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null | {
"abstract": " During the start of a survey program using FORS2 long slit spectroscopy on\nplanetary nebulae (PN) and their haloes, we serendipitously discovered six\nbackground emission line galaxies (ELG) with redshifts of z = 0.2057, 0.3137,\n0.37281, 0.4939, 0.7424 and 0.8668. Thus they clearly do not belong to a common\ncluster structure. We derived the major physical properties of the targets.\nSince the used long slit covers a sky area of only 570 arcsec^2, we discuss\nfurther potential of serendipitous discoveries in archival data, beside the\ndeep systematic work of the ongoing and upcoming big surveys. We conclude that\narchival data provide a decent potential for extending the overall data on ELGs\nwithout any selection bias.\n",
"title": "Emission line galaxies behind the planetary nebula IC 5148: Potential for a serendipity survey with archival data"
} | null | null | null | null | true | null | 2901 | null | Default | null | null |
null | {
"abstract": " For $n\\in \\mathbb{N}$ let $S_n$ be the smallest number $S>0$ satisfying the\ninequality $$ \\int_K f \\le S \\cdot |K|^{\\frac 1n} \\cdot \\max_{\\xi\\in S^{n-1}}\n\\int_{K\\cap \\xi^\\bot} f $$ for all centrally-symmetric convex bodies $K$ in\n$\\mathbb{R}^n$ and all even, continuous probability densities $f$ on $K$. Here\n$|K|$ is the volume of $K$. It was proved by the second-named author that\n$S_n\\le 2\\sqrt{n}$, and in analogy with Bourgain's slicing problem, it was\nasked whether $S_n$ is bounded from above by a universal constant. In this note\nwe construct an example showing that $S_n\\ge c\\sqrt{n}/\\sqrt{\\log \\log n},$\nwhere $c > 0$ is an absolute constant. Additionally, for any $0 < \\alpha < 2$\nwe describe a related example that satisfies the so-called\n$\\psi_{\\alpha}$-condition.\n",
"title": "An example related to the slicing inequality for general measures"
} | null | null | null | null | true | null | 2902 | null | Default | null | null |
null | {
"abstract": " The advection equation is the basis for mathematical models of continuum\nmechanics. In the approximate solution of nonstationary problems it is\nnecessary to inherit main properties of the conservatism and monotonicity of\nthe solution. In this paper, the advection equation is written in the symmetric\nform, where the advection operator is the half-sum of advection operators in\nconservative (divergent) and non-conservative (characteristic) forms. The\nadvection operator is skew-symmetric. Standard finite element approximations in\nspace are used. The standart explicit two-level scheme for the advection\nequation is absolutly unstable. New conditionally stable regularized schemes\nare constructed, on the basis of the general theory of stability\n(well-posedness) of operator-difference schemes, the stability conditions of\nthe explicit Lax-Wendroff scheme are established. Unconditionally stable and\nconservative schemes are implicit schemes of the second (Crank-Nicolson scheme)\nand fourth order. The conditionally stable implicit Lax-Wendroff scheme is\nconstructed. The accuracy of the investigated explicit and implicit two-level\nschemes for an approximate solution of the advection equation is illustrated by\nthe numerical results of a model two-dimensional problem.\n",
"title": "Two-level schemes for the advection equation"
} | null | null | null | null | true | null | 2903 | null | Default | null | null |
null | {
"abstract": " Functional time series have become an integral part of both functional data\nand time series analysis. Important contributions to methodology, theory and\napplication for the prediction of future trajectories and the estimation of\nfunctional time series parameters have been made in the recent past. This paper\ncontinues this line of research by proposing a first principled approach to\nestimate invertible functional time series by fitting functional moving average\nprocesses. The idea is to estimate the coefficient operators in a functional\nlinear filter. To do this a functional Innovations Algorithm is utilized as a\nstarting point to estimate the corresponding moving average operators via\nsuitable projections into principal directions. In order to establish\nconsistency of the proposed estimators, asymptotic theory is developed for\nincreasing subspaces of these principal directions. For practical purposes,\nseveral strategies to select the number of principal directions to include in\nthe estimation procedure as well as the choice of order of the functional\nmoving average process are discussed. Their empirical performance is evaluated\nthrough simulations and an application to vehicle traffic data.\n",
"title": "Estimating functional time series by moving average model fitting"
} | null | null | [
"Statistics"
]
| null | true | null | 2904 | null | Validated | null | null |
null | {
"abstract": " Benford's law is an empirical observation, first reported by Simon Newcomb in\n1881 and then independently by Frank Benford in 1938: the first significant\ndigits of numbers in large data are often distributed according to a\nlogarithmically decreasing function. Being contrary to intuition, the law was\nforgotten as a mere curious observation. However, in the last two decades,\nrelevant literature has grown exponentially, - an evolution typical of\n\"Sleeping Beauties\" (SBs) publications that go unnoticed (sleep) for a long\ntime and then suddenly become center of attention (are awakened). Thus, in the\npresent study, we show that Newcomb (1881) and Benford (1938) papers are\nclearly SBs. The former was in deep sleep for 110 years whereas the latter was\nin deep sleep for a comparatively lesser period of 31 years up to 1968, and in\na state of less deep sleep for another 27 years up to 1995. Both SBs were\nawakened in the year 1995 by Hill (1995a). In so doing, we show that the waking\nprince (Hill, 1995a) is more often quoted than the SB whom he kissed, - in this\nBenford's law case, wondering whether this is a general effect, - to be\nusefully studied.\n",
"title": "Benford's law: a 'sleeping beauty' sleeping in the dirty pages of logarithmic tables"
} | null | null | null | null | true | null | 2905 | null | Default | null | null |
null | {
"abstract": " Synchronization, that occurs both for non-chaotic and chaotic systems, is a\nstriking phenomenon with many practical implications in natural phenomena.\nHowever, even before synchronization, strong correlations occur in the\ncollective dynamics of complex systems. To characterize their nature is\nessential for the understanding of phenomena in physical and social sciences.\nThe emergence of strong correlations before synchronization is illustrated in a\nfew piecewise linear models. They are shown to be associated to the behavior of\nergodic parameters which may be exactly computed in some models. The models are\nalso used as a testing ground to find general methods to characterize and\nparametrize the correlated nature of collective dynamics.\n",
"title": "Characterizing correlations and synchronization in collective dynamics"
} | null | null | null | null | true | null | 2906 | null | Default | null | null |
null | {
"abstract": " The deformation of disordered solids relies on swift and localised\nrearrangements of particles. The inspection of soft vibrational modes can help\npredict the locations of these rearrangements, while the strain that they\nactually redistribute mediates collective effects. Here, we study soft modes\nand strain redistribution in a two-dimensional continuous mesoscopic model\nbased on a Ginzburg-Landau free energy for perfect solids, supplemented with a\nplastic disorder potential that accounts for shear softening and\nrearrangements. Regardless of the disorder strength, our numerical simulations\nshow soft modes that are always sharply peaked at the softest point of the\nmaterial (unlike what happens for the depinning of an elastic interface).\nContrary to widespread views, the deformation halo around this peak does not\nalways have a quadrupolar (Eshelby-like) shape. Instead, for finite and\nnarrowly-distributed disorder, it looks like a fracture, with a strain field\nthat concentrates along some easy directions. These findings are rationalised\nwith analytical calculations in the case where the plastic disorder is confined\nto a point-like `impurity'. In this case, we unveil a continuous family of\nelastic propagators, which are identical for the soft modes and for the\nequilibrium configurations. This family interpolates between the standard\nquadrupolar propagator and the fracture-like one as the anisotropy of the\nelastic medium is increased. Therefore, we expect to see a fracture-like\npropagator when extended regions on the brink of failure have already softened\nalong the shear direction and thus rendered the material anisotropic, but not\nfailed yet. We speculate that this might be the case in carefully aged glasses\njust before macroscopic failure.\n",
"title": "Soft modes and strain redistribution in continuous models of amorphous plasticity: the Eshelby paradigm, and beyond?"
} | null | null | null | null | true | null | 2907 | null | Default | null | null |
null | {
"abstract": " The reproducing kernel Hilbert space (RKHS) embedding of distributions offers\na general and flexible framework for testing problems in arbitrary domains and\nhas attracted considerable amount of attention in recent years. To gain\ninsights into their operating characteristics, we study here the statistical\nperformance of such approaches within a minimax framework. Focusing on the case\nof goodness-of-fit tests, our analyses show that a vanilla version of the\nkernel-embedding based test could be suboptimal, and suggest a simple remedy by\nmoderating the embedding. We prove that the moderated approach provides optimal\ntests for a wide range of deviations from the null and can also be made\nadaptive over a large collection of interpolation spaces. Numerical experiments\nare presented to further demonstrate the merits of our approach.\n",
"title": "On the Optimality of Kernel-Embedding Based Goodness-of-Fit Tests"
} | null | null | null | null | true | null | 2908 | null | Default | null | null |
null | {
"abstract": " In this work we consider the presence of contrarian agents in discrete\n3-state kinetic exchange opinion models. The contrarians are individuals that\nadopt the choice opposite to the prevailing choice of their contacts, whatever\nthis choice is. We consider binary as well as three-agent interactions, with\nstochastic parameters, in a fully-connected population. Our numerical results\nsuggest that the presence of contrarians destroys the absorbing state of the\noriginal model, changing the transition to the para-ferromagnetic type. In this\ncase, the consequence for the society is that the three opinions coexist in the\npopulation, in both phases (ordered and disordered). Furthermore, the\norder-disorder transition is suppressed for a sufficient large fraction of\ncontrarians. In some cases the transition is discontinuous, and it changes to\ncontinuous before it is suppressed. Some of our results are complemented by\nanalytical calculations based on the master equation.\n",
"title": "The influence of contrarians in the dynamics of opinion formation"
} | null | null | [
"Physics"
]
| null | true | null | 2909 | null | Validated | null | null |
null | {
"abstract": " We develop a unified valuation theory that incorporates credit risk\n(defaults), collateralization and funding costs, by expanding the replication\napproach to a generality that has not yet been studied previously and reaching\nvaluation when replication is not assumed. This unifying theoretical framework\nclarifies the relationship between the two valuation approaches: the adjusted\ncash flows approach pioneered for example by Brigo, Pallavicini and co-authors\n([12, 13, 34]) and the classic replication approach illustrated for example by\nBielecki and Rutkowski and co-authors ([3, 8]). In particular, results of this\nwork cover most previous papers where the authors studied specific replication\nmodels.\n",
"title": "Risk-neutral valuation under differential funding costs, defaults and collateralization"
} | null | null | [
"Quantitative Finance"
]
| null | true | null | 2910 | null | Validated | null | null |
null | {
"abstract": " We use trace class scattering theory to exclude the possibility of absolutely\ncontinuous spectrum in a large class of self-adjoint operators with an\nunderlying hierarchical structure and provide applications to certain random\nhierarchical operators and matrices. We proceed to contrast the localizing\neffect of the hierarchical structure in the deterministic setting with previous\nresults and conjectures in the random setting. Furthermore, we survey stronger\nlocalization statements truly exploiting the disorder for the hierarchical\nAnderson model and report recent results concerning the spectral statistics of\nthe ultrametric random matrix ensemble.\n",
"title": "Singular Spectrum and Recent Results on Hierarchical Operators"
} | null | null | null | null | true | null | 2911 | null | Default | null | null |
null | {
"abstract": " Weyl fermions are shown to exist inside a parabolic band, where the kinetic\nenergy of carriers is given by the non-relativistic Schroedinger equation.\nThere are Fermi arcs as a direct consequence of the folding of a ring shaped\nFermi surface inside the first Brillouin zone. Our results stem from the\ndecomposition of the kinetic energy into the sum of the square of the Weyl\nstate, the coupling to the local magnetic field and the Rashba interaction. The\nWeyl fermions break the time and reflection symmetries present in the kinetic\nenergy, thus allowing for the onset of a weak three-dimensional magnetic field\naround the layer. This field brings topological stability to the current\ncarrying states through a Chern number. In the special limit that the Weyl\nstate becomes gapless this magnetic interaction is shown to be purely\nattractive, thus suggesting the onset of a superconducting condensate of zero\nhelicity states.\n",
"title": "Weyl states and Fermi arcs in parabolic bands"
} | null | null | null | null | true | null | 2912 | null | Default | null | null |
null | {
"abstract": " The recent success of Deep Neural Networks (DNNs) has drastically improved\nthe state of the art for many application domains. While achieving high\naccuracy performance, deploying state-of-the-art DNNs is a challenge since they\ntypically require billions of expensive arithmetic computations. In addition,\nDNNs are typically deployed in ensemble to boost accuracy performance, which\nfurther exacerbates the system requirements. This computational overhead is an\nissue for many platforms, e.g. data centers and embedded systems, with tight\nlatency and energy budgets. In this article, we introduce flexible DNNs\nensemble processing technique, which achieves large reduction in average\ninference latency while incurring small to negligible accuracy drop. Our\ntechnique is flexible in that it allows for dynamic adaptation between quality\nof results (QoR) and execution runtime. We demonstrate the effectiveness of the\ntechnique on AlexNet and ResNet-50 using the ImageNet dataset. This technique\ncan also easily handle other types of networks.\n",
"title": "Flexible Deep Neural Network Processing"
} | null | null | null | null | true | null | 2913 | null | Default | null | null |
null | {
"abstract": " Despite a long record of intense efforts, the basic mechanisms by which\ndissipation emerges from the microscopic dynamics of a relativistic fluid still\nelude a complete understanding. In particular, no unique pathway from kinetic\ntheory to hydrodynamics has been identified as yet, with different approaches\nleading to different values of the transport coefficients. In this Letter, we\napproach the problem by matching data from lattice kinetic simulations with\nanalytical predictions. Our numerical results provide neat evidence in favour\nof the Chapman-Enskog procedure, as suggested by recently theoretical analyses,\nalong with qualitative hints at the basic reasons why the Chapman-Enskog\nexpansion might be better suited than Grad's method to capture the emergence of\ndissipative effects in relativistic fluids.\n",
"title": "Kinetic approach to relativistic dissipation"
} | null | null | null | null | true | null | 2914 | null | Default | null | null |
null | {
"abstract": " This paper addresses image classification through learning a compact and\ndiscriminative dictionary efficiently. Given a structured dictionary with each\natom (columns in the dictionary matrix) related to some label, we propose\ncross-label suppression constraint to enlarge the difference among\nrepresentations for different classes. Meanwhile, we introduce group\nregularization to enforce representations to preserve label properties of\noriginal samples, meaning the representations for the same class are encouraged\nto be similar. Upon the cross-label suppression, we don't resort to\nfrequently-used $\\ell_0$-norm or $\\ell_1$-norm for coding, and obtain\ncomputational efficiency without losing the discriminative power for\ncategorization. Moreover, two simple classification schemes are also developed\nto take full advantage of the learnt dictionary. Extensive experiments on six\ndata sets including face recognition, object categorization, scene\nclassification, texture recognition and sport action categorization are\nconducted, and the results show that the proposed approach can outperform lots\nof recently presented dictionary algorithms on both recognition accuracy and\ncomputational efficiency.\n",
"title": "Cross-label Suppression: A Discriminative and Fast Dictionary Learning with Group Regularization"
} | null | null | [
"Computer Science",
"Statistics"
]
| null | true | null | 2915 | null | Validated | null | null |
null | {
"abstract": " Recurrent neural nets (RNN) and convolutional neural nets (CNN) are widely\nused on NLP tasks to capture the long-term and local dependencies,\nrespectively. Attention mechanisms have recently attracted enormous interest\ndue to their highly parallelizable computation, significantly less training\ntime, and flexibility in modeling dependencies. We propose a novel attention\nmechanism in which the attention between elements from input sequence(s) is\ndirectional and multi-dimensional (i.e., feature-wise). A light-weight neural\nnet, \"Directional Self-Attention Network (DiSAN)\", is then proposed to learn\nsentence embedding, based solely on the proposed attention without any RNN/CNN\nstructure. DiSAN is only composed of a directional self-attention with temporal\norder encoded, followed by a multi-dimensional attention that compresses the\nsequence into a vector representation. Despite its simple form, DiSAN\noutperforms complicated RNN models on both prediction quality and time\nefficiency. It achieves the best test accuracy among all sentence encoding\nmethods and improves the most recent best result by 1.02% on the Stanford\nNatural Language Inference (SNLI) dataset, and shows state-of-the-art test\naccuracy on the Stanford Sentiment Treebank (SST), Multi-Genre natural language\ninference (MultiNLI), Sentences Involving Compositional Knowledge (SICK),\nCustomer Review, MPQA, TREC question-type classification and Subjectivity\n(SUBJ) datasets.\n",
"title": "DiSAN: Directional Self-Attention Network for RNN/CNN-Free Language Understanding"
} | null | null | null | null | true | null | 2916 | null | Default | null | null |
null | {
"abstract": " We derive new estimates for the number of discrete eigenvalues of compactly\nperturbed operators on Banach spaces, assuming that the perturbing operator is\nan element of a weak entropy number ideal. Our results improve upon earlier\nresults by the author and by Demuth et al. The main tool in our proofs is an\ninequality of Carl. In particular, in contrast to all previous results we do\nnot rely on tools from complex analysis.\n",
"title": "Eigenvalues of compactly perturbed operators via entropy numbers"
} | null | null | null | null | true | null | 2917 | null | Default | null | null |
null | {
"abstract": " Recently low displacement rank (LDR) matrices, or so-called structured\nmatrices, have been proposed to compress large-scale neural networks. Empirical\nresults have shown that neural networks with weight matrices of LDR matrices,\nreferred as LDR neural networks, can achieve significant reduction in space and\ncomputational complexity while retaining high accuracy. We formally study LDR\nmatrices in deep learning. First, we prove the universal approximation property\nof LDR neural networks with a mild condition on the displacement operators. We\nthen show that the error bounds of LDR neural networks are as efficient as\ngeneral neural networks with both single-layer and multiple-layer structure.\nFinally, we propose back-propagation based training algorithm for general LDR\nneural networks.\n",
"title": "Theoretical Properties for Neural Networks with Weight Matrices of Low Displacement Rank"
} | null | null | null | null | true | null | 2918 | null | Default | null | null |
null | {
"abstract": " Classification rules can be severely affected by the presence of disturbing\nobservations in the training sample. Looking for an optimal classifier with\nsuch data may lead to unnecessarily complex rules. So, simpler effective\nclassification rules could be achieved if we relax the goal of fitting a good\nrule for the whole training sample but only consider a fraction of the data. In\nthis paper we introduce a new method based on trimming to produce\nclassification rules with guaranteed performance on a significant fraction of\nthe data. In particular, we provide an automatic way of determining the right\ntrimming proportion and obtain in this setting oracle bounds for the\nclassification error on the new data set.\n",
"title": "A data driven trimming procedure for robust classification"
} | null | null | null | null | true | null | 2919 | null | Default | null | null |
null | {
"abstract": " Finding the exact integrality gap $\\alpha$ for the LP relaxation of the\nmetric Travelling Salesman Problem (TSP) has been an open problem for over\nthirty years, with little progress made. It is known that $4/3 \\leq \\alpha \\leq\n3/2$, and a famous conjecture states $\\alpha = 4/3$. For this problem,\nessentially two \"fundamental\" classes of instances have been proposed. This\nfundamental property means that in order to show that the integrality gap is at\nmost $\\rho$ for all instances of metric TSP, it is sufficient to show it only\nfor the instances in the fundamental class. However, despite the importance and\nthe simplicity of such classes, no apparent effort has been deployed for\nimproving the integrality gap bounds for them. In this paper we take a natural\nfirst step in this endeavour, and consider the $1/2$-integer points of one such\nclass. We successfully improve the upper bound for the integrality gap from\n$3/2$ to $10/7$ for a superclass of these points, as well as prove a lower\nbound of $4/3$ for the superclass. Our methods involve innovative applications\nof tools from combinatorial optimization which have the potential to be more\nbroadly applied.\n",
"title": "The Salesman's Improved Tours for Fundamental Classes"
} | null | null | null | null | true | null | 2920 | null | Default | null | null |
null | {
"abstract": " Gaussian mixture models are widely used in Statistics. A fundamental aspect\nof these distributions is the study of the local maxima of the density, or\nmodes. In particular, it is not known how many modes a mixture of $k$ Gaussians\nin $d$ dimensions can have. We give a brief account of this problem's history.\nThen, we give improved lower bounds and the first upper bound on the maximum\nnumber of modes, provided it is finite.\n",
"title": "Maximum Number of Modes of Gaussian Mixtures"
} | null | null | null | null | true | null | 2921 | null | Default | null | null |
null | {
"abstract": " In this paper we will consider a generalized extension of the Eisenberg-Noe\nmodel of financial contagion to allow for time dynamics in both discrete and\ncontinuous time. Derivation and interpretation of the financial implications\nwill be provided. Emphasis will be placed on the continuous-time framework and\nits formulation as a differential equation driven by the operating cash flows.\nMathematical results on existence and uniqueness of firm wealths under the\ndiscrete and continuous-time models will be provided. Finally, the financial\nimplications of time dynamics will be considered. The focus will be on how the\ndynamic clearing solutions differ from those of the static Eisenberg-Noe model.\n",
"title": "Dynamic Clearing and Contagion in Financial Networks"
} | null | null | null | null | true | null | 2922 | null | Default | null | null |
null | {
"abstract": " Intensionality is a phenomenon that occurs in logic and computation. In the\nmost general sense, a function is intensional if it operates at a level finer\nthan (extensional) equality. This is a familiar setting for computer\nscientists, who often study different programs or processes that are\ninterchangeable, i.e. extensionally equal, even though they are not implemented\nin the same way, so intensionally distinct. Concomitant with intensionality is\nthe phenomenon of intensional recursion, which refers to the ability of a\nprogram to have access to its own code. In computability theory, intensional\nrecursion is enabled by Kleene's Second Recursion Theorem. This thesis is\nconcerned with the crafting of a logical toolkit through which these phenomena\ncan be studied. Our main contribution is a framework in which mathematical and\ncomputational constructions can be considered either extensionally, i.e. as\nabstract values, or intensionally, i.e. as fine-grained descriptions of their\nconstruction. Once this is achieved, it may be used to analyse intensional\nrecursion.\n",
"title": "On the Semantics of Intensionality and Intensional Recursion"
} | null | null | null | null | true | null | 2923 | null | Default | null | null |
null | {
"abstract": " This two-part paper details a theory of solvability for the power flow\nequations in lossless power networks. In Part I, we derive a new formulation of\nthe lossless power flow equations, which we term the fixed-point power flow.\nThe model is stated for both meshed and radial networks, and is parameterized\nby several graph-theoretic matrices -- the power network stiffness matrices --\nwhich quantify the internal coupling strength of the network. The model leads\nimmediately to an explicit approximation of the high-voltage power flow\nsolution. For standard test cases, we find that iterates of the fixed-point\npower flow converge rapidly to the high-voltage power flow solution, with the\napproximate solution yielding accurate predictions near base case loading. In\nPart II, we leverage the fixed-point power flow to study power flow\nsolvability, and for radial networks we derive conditions guaranteeing the\nexistence and uniqueness of a high-voltage power flow solution. These\nconditions (i) imply exponential convergence of the fixed-point power flow\niteration, and (ii) properly generalize the textbook two-bus system results.\n",
"title": "A Theory of Solvability for Lossless Power Flow Equations -- Part I: Fixed-Point Power Flow"
} | null | null | null | null | true | null | 2924 | null | Default | null | null |
null | {
"abstract": " It is a neat result from functional programming that libraries of parser\ncombinators can support rapid construction of decoders for quite a range of\nformats. With a little more work, the same combinator program can denote both a\ndecoder and an encoder. Unfortunately, the real world is full of gnarly\nformats, as with the packet formats that make up the standard Internet protocol\nstack. Most past parser-combinator approaches cannot handle these formats, and\nthe few exceptions require redundancy -- one part of the natural grammar needs\nto be hand-translated into hints in multiple parts of a parser program. We show\nhow to recover very natural and nonredundant format specifications, covering\nall popular network packet formats and generating both decoders and encoders\nautomatically. The catch is that we use the Coq proof assistant to derive both\nkinds of artifacts using tactics, automatically, in a way that guarantees that\nthey form inverses of each other. We used our approach to reimplement packet\nprocessing for a full Internet protocol stack, inserting our replacement into\nthe OCaml-based MirageOS unikernel, resulting in minimal performance\ndegradation.\n",
"title": "Narcissus: Deriving Correct-By-Construction Decoders and Encoders from Binary Formats"
} | null | null | null | null | true | null | 2925 | null | Default | null | null |
null | {
"abstract": " In this article we study the role of the Green function for the Laplacian in\na compact Riemannian manifold as a tool for obtaining well-distributed points.\nIn particular, we prove that a sequence of minimizers for the Green energy is\nasymptotically uniformly distributed. We pay special attention to the case of\nlocally harmonic manifolds.\n",
"title": "Discrete and Continuous Green Energy on Compact Manifolds"
} | null | null | null | null | true | null | 2926 | null | Default | null | null |
null | {
"abstract": " The rising need of secret image sharing with high security has led to much\nadvancement in lucrative exchange of important images which contain vital and\nconfidential information. Multi secret image sharing system (MSIS) is an\nefficient and robust method for transmitting one or more secret images\nsecurely. In recent research, n secret images are encrypted into n or n+ 1\nshared images and stored in different database servers. The decoder has to\nreceive all n or n+1 encrypted images to reproduce the secret image. One can\nrecover partial secret information from n-1 or fewer shared images, which poses\nrisk for the confidential information encrypted. In this proposed paper we\ndeveloped a novel algorithm to increase the sharing capacity by using (n, n/8)\nmulti-secret sharing scheme with increased security by generating a unique\nsecurity key. A unrevealed comparison image is used to produce shares which\nmakes the secret image invulnerable to the hackers\n",
"title": "High Capacity, Secure (n, n/8) Multi Secret Image Sharing Scheme with Security Key"
} | null | null | null | null | true | null | 2927 | null | Default | null | null |
null | {
"abstract": " In this paper we introduce MATMPC, an open source software built in MATLAB\nfor nonlinear model predictive control (NMPC). It is designed to facilitate\nmodelling, controller design and simulation for a wide class of NMPC\napplications. MATMPC has a number of algorithmic modules, including automatic\ndifferentiation, direct multiple shooting, condensing, linear quadratic program\n(QP) solver and globalization. It also supports a unique Curvature-like Measure\nof Nonlinearity (CMoN) MPC algorithm. MATMPC has been designed to provide\nstate-of-the-art performance while making the prototyping easy, also with\nlimited programming knowledge. This is achieved by writing each module directly\nin MATLAB API for C. As a result, MATMPC modules can be compiled into MEX\nfunctions with performance comparable to plain C/C++ solvers. MATMPC has been\nsuccessfully used in operating systems including WINDOWS, LINUX AND OS X.\nSelected examples are shown to highlight the effectiveness of MATMPC.\n",
"title": "MATMPC - A MATLAB Based Toolbox for Real-time Nonlinear Model Predictive Control"
} | null | null | null | null | true | null | 2928 | null | Default | null | null |
null | {
"abstract": " We propose a copula based method to handle missing values in multivariate\ndata of mixed types in multilevel data sets. Building upon the extended rank\nlikelihood of \\cite{hoff2007extending} and the multinomial probit model, our\nmodel is a latent variable model which is able to capture the relationship\namong variables of different types as well as accounting for the clustering\nstructure. We fit the model by approximating the posterior distribution of the\nparameters and the missing values through a Gibbs sampling scheme. We use the\nmultiple imputation procedure to incorporate the uncertainty due to missing\nvalues in the analysis of the data. Our proposed method is evaluated through\nsimulations to compare it with several conventional methods of handling missing\ndata. We also apply our method to a data set from a cluster randomized\ncontrolled trial of a multidisciplinary intervention in acute stroke units. We\nconclude that our proposed copula based imputation model for mixed type\nvariables achieves reasonably good imputation accuracy and recovery of\nparameters in some models of interest, and that adding random effects enhances\nperformance when the clustering effect is strong.\n",
"title": "A Copula-based Imputation Model for Missing Data of Mixed Type in Multilevel Data Sets"
} | null | null | [
"Statistics"
]
| null | true | null | 2929 | null | Validated | null | null |
null | {
"abstract": " Cooling the rotation and the vibration of molecules by broadband light\nsources was possible for trapped molecular ions or ultracold molecules. Because\nof a low power spectral density, the cooling timescale has never fell below\nthan a few milliseconds. Here we report on rotational and vibrational cooling\nof a supersonic beam of barium monofluoride molecules in less than 440 $\\mu$s.\nVibrational cooling was optimized by enhancing the spectral power density of a\nsemiconductor light source at the underlying molecular transitions allowing us\nto transfer all the populations of $v''=1-3$ into the vibrational ground state\n($v''=0$). Rotational cooling, that requires an efficient vibrational pumping,\nwas then achieved. According to a Boltzmann fit, the rotation temperature was\nreduced by almost a factor of 10. In this fashion, the population of the lowest\nrotational levels increased by more than one order of magnitude.\n",
"title": "Rovibrational optical cooling of a molecular beam"
} | null | null | [
"Physics"
]
| null | true | null | 2930 | null | Validated | null | null |
null | {
"abstract": " Numerous pattern recognition applications can be formed as learning from\ngraph-structured data, including social network, protein-interaction network,\nthe world wide web data, knowledge graph, etc. While convolutional neural\nnetwork (CNN) facilitates great advances in gridded image/video understanding\ntasks, very limited attention has been devoted to transform these successful\nnetwork structures (including Inception net, Residual net, Dense net, etc.) to\nestablish convolutional networks on graph, due to its irregularity and\ncomplexity geometric topologies (unordered vertices, unfixed number of adjacent\nedges/vertices). In this paper, we aim to give a comprehensive analysis of when\nwork matters by transforming different classical network structures to graph\nCNN, particularly in the basic graph recognition problem. Specifically, we\nfirstly review the general graph CNN methods, especially in its spectral\nfiltering operation on the irregular graph data. We then introduce the basic\nstructures of ResNet, Inception and DenseNet into graph CNN and construct these\nnetwork structures on graph, named as G_ResNet, G_Inception, G_DenseNet. In\nparticular, it seeks to help graph CNNs by shedding light on how these\nclassical network structures work and providing guidelines for choosing\nappropriate graph network frameworks. Finally, we comprehensively evaluate the\nperformance of these different network structures on several public graph\ndatasets (including social networks and bioinformatic datasets), and\ndemonstrate how different network structures work on graph CNN in the graph\nrecognition task.\n",
"title": "When Work Matters: Transforming Classical Network Structures to Graph CNN"
} | null | null | null | null | true | null | 2931 | null | Default | null | null |
null | {
"abstract": " When participating in electricity markets, owners of battery energy storage\nsystems must bid in such a way that their revenues will at least cover their\ntrue cost of operation. Since cycle aging of battery cells represents a\nsubstantial part of this operating cost, the cost of battery degradation must\nbe factored in these bids. However, existing models of battery degradation\neither do not fit market clearing software or do not reflect the actual battery\naging mechanism. In this paper we model battery cycle aging using a piecewise\nlinear cost function, an approach that provides a close approximation of the\ncycle aging mechanism of electrochemical batteries and can be incorporated\neasily into existing market dispatch programs. By defining the marginal aging\ncost of each battery cycle, we can assess the actual operating profitability of\nbatteries. A case study demonstrates the effectiveness of the proposed model in\nmaximizing the operating profit of a battery energy storage system taking part\nin the ISO New England energy and reserve markets.\n",
"title": "Factoring the Cycle Aging Cost of Batteries Participating in Electricity Markets"
} | null | null | [
"Mathematics"
]
| null | true | null | 2932 | null | Validated | null | null |
null | {
"abstract": " We design and analyse variations of the classical Thompson sampling (TS)\nprocedure for Bayesian optimisation (BO) in settings where function evaluations\nare expensive, but can be performed in parallel. Our theoretical analysis shows\nthat a direct application of the sequential Thompson sampling algorithm in\neither synchronous or asynchronous parallel settings yields a surprisingly\npowerful result: making $n$ evaluations distributed among $M$ workers is\nessentially equivalent to performing $n$ evaluations in sequence. Further, by\nmodeling the time taken to complete a function evaluation, we show that, under\na time constraint, asynchronously parallel TS achieves asymptotically lower\nregret than both the synchronous and sequential versions. These results are\ncomplemented by an experimental analysis, showing that asynchronous TS\noutperforms a suite of existing parallel BO algorithms in simulations and in a\nhyper-parameter tuning application in convolutional neural networks. In\naddition to these, the proposed procedure is conceptually and computationally\nmuch simpler than existing work for parallel BO.\n",
"title": "Asynchronous Parallel Bayesian Optimisation via Thompson Sampling"
} | null | null | null | null | true | null | 2933 | null | Default | null | null |
null | {
"abstract": " We experimentally study steady Marangoni-driven surfactant transport on the\ninterface of a deep water layer. Using hydrodynamic measurements, and without\nusing any knowledge of the surfactant physico-chemical properties, we show that\nsodium dodecyl sulphate and Tergitol 15-S-9 introduced in low concentrations\nresult in a flow driven by adsorbed surfactant. At higher surfactant\nconcentration, the flow is dominated by the dissolved surfactant. Using\nCamphoric acid, whose properties are {\\it a priori} unknown, we demonstrate\nthis method's efficacy by showing its spreading is adsorption dominated.\n",
"title": "Hydrodynamic signatures of stationary Marangoni-driven surfactant transport"
} | null | null | null | null | true | null | 2934 | null | Default | null | null |
null | {
"abstract": " We study the asymptotic behavior of the homotopy groups of simply connected\nfinite $p$-local complexes, and define a space to be locally hyperbolic if its\nhomotopy groups have exponential growth. Under some certain conditions related\nto the functorial decomposition of loop suspension, we prove that the suspended\nfinite complexes are locally hyperbolic if suitable but accessible information\nof the homotopy groups is known. In particular, we prove that Moore spaces are\nlocally hyperbolic, and other candidates are also given.\n",
"title": "Exponential growth of homotopy groups of suspended finite complexes"
} | null | null | [
"Mathematics"
]
| null | true | null | 2935 | null | Validated | null | null |
null | {
"abstract": " In rectangle packing problems we are given the task of placing axis-aligned\nrectangles in a given plane region, so that they do not overlap with each\nother. In Maximum Weight Independent Set of Rectangles (MWISR), their position\nis given and we can only select which rectangles to choose, while trying to\nmaximize their total weight. In Strip Packing (SP), we have to pack all the\ngiven rectangles in a rectangular region of fixed width, while minimizing its\nheight. In 2-Dimensional Geometric Knapsack (2DGK), the target region is a\nsquare of a given size, and our goal is to select and pack a subset of the\ngiven rectangles of maximum weight. We study a generalization of MWISR and use\nit to improve the approximation for a resource allocation problem called\nbagUFP. We revisit some classical results on SP and 2DGK, by proposing a\nframework based on smaller containers that are packed with simpler rules; while\nvariations of this scheme are indeed a standard technique in this area, we\nabstract away some of the problem-specific differences, obtaining simpler\nalgorithms that work for different problems. We obtain improved approximations\nfor SP in pseudo-polynomial time, and for a variant of 2DGK where one can to\nrotate the rectangles by 90°. For the latter, we propose the first\nalgorithms with approximation factor better than 2. For the main variant of\n2DGK (without rotations), a container-based approach seems to face a natural\nbarrier of 2 in the approximation factor. Thus, we consider a generalized kind\nof packing that combines container packings with another packing problem that\nwe call L-packing problem, where we have to pack rectangles in an L-shaped\nregion of the plane. By finding a (1 + {\\epsilon})-approximation for this\nproblem and exploiting the combinatorial structure of 2DGK, we obtain the first\nalgorithms that break the barrier of 2 for the approximation factor of this\nproblem.\n",
"title": "Approximation Algorithms for Rectangle Packing Problems (PhD Thesis)"
} | null | null | null | null | true | null | 2936 | null | Default | null | null |
null | {
"abstract": " The aim of this work is to study the existence of a periodic solutions of\nthird order differential equations $z'''(t) = Az(t) + f(t)$ with the periodic\ncondition $x(0) = x(2\\pi), x'(0) = x'(2\\pi)$ and $x''(0) = x''(2\\pi)$. Our\napproach is based on the R-boundedness and $L^{p}$-multiplier of linear\noperators.\n",
"title": "R-boundedness Approach to linear third differential equations in a UMD Space"
} | null | null | [
"Mathematics"
]
| null | true | null | 2937 | null | Validated | null | null |
null | {
"abstract": " Understanding the entanglement structure of out-of-equilibrium many-body\nsystems is a challenging yet revealing task. Here we investigate the\nentanglement dynamics after a quench from a piecewise homogeneous initial state\nin integrable systems. This is the prototypical setup for studying quantum\ntransport, and it consists in the sudden junction of two macroscopically\ndifferent and homogeneous states. By exploiting the recently developed\nintegrable hydrodynamic approach and the quasiparticle picture for the\nentanglement dynamics, we conjecture a formula for the entanglement production\nrate after joining two semi-infinite reservoirs, as well as the steady-state\nentanglement entropy of a finite subregion. We show that both quantities are\ndetermined by the quasiparticles created in the Non Equilibrium steady State\n(NESS) appearing at large times at the interface between the two reservoirs.\nSpecifically, the steady-state entropy coincides with the thermodynamic entropy\nof the NESS, whereas the entropy production rate reflects its spreading into\nthe bulk of the two reservoirs. Our results are numerically corroborated using\ntime-dependent Density Matrix Renormalization Group (tDMRG) simulations in the\nparadigmatic XXZ spin-1/2 chain.\n",
"title": "Entanglement and quantum transport in integrable systems"
} | null | null | null | null | true | null | 2938 | null | Default | null | null |
null | {
"abstract": " Transfer learning has the potential to reduce the burden of data collection\nand to decrease the unavoidable risks of the training phase. In this letter, we\nintroduce a multirobot, multitask transfer learning framework that allows a\nsystem to complete a task by learning from a few demonstrations of another task\nexecuted on another system. We focus on the trajectory tracking problem where\neach trajectory represents a different task, since many robotic tasks can be\ndescribed as a trajectory tracking problem. The proposed multirobot transfer\nlearning framework is based on a combined $\\mathcal{L}_1$ adaptive control and\nan iterative learning control approach. The key idea is that the adaptive\ncontroller forces dynamically different systems to behave as a specified\nreference model. The proposed multitask transfer learning framework uses\ntheoretical control results (e.g., the concept of vector relative degree) to\nlearn a map from desired trajectories to the inputs that make the system track\nthese trajectories with high accuracy. This map is used to calculate the inputs\nfor a new, unseen trajectory. Experimental results using two different\nquadrotor platforms and six different trajectories show that, on average, the\nproposed framework reduces the first-iteration tracking error by 74% when\ninformation from tracking a different single trajectory on a different\nquadrotor is utilized.\n",
"title": "Data-Efficient Multirobot, Multitask Transfer Learning for Trajectory Tracking"
} | null | null | null | null | true | null | 2939 | null | Default | null | null |
null | {
"abstract": " The Erdős-Ginzburg-Ziv constant of an abelian group $G$, denoted\n$\\mathfrak{s}(G)$, is the smallest $k\\in\\mathbb{N}$ such that any sequence of\nelements of $G$ of length $k$ contains a zero-sum subsequence of length\n$\\exp(G)$. In this paper, we use the partition rank, which generalizes the\nslice rank, to prove that for any odd prime $p$, \\[\n\\mathfrak{s}\\left(\\mathbb{F}_{p}^{n}\\right)\\leq(p-1)2^{p}\\left(J(p)\\cdot\np\\right)^{n} \\] where $0.8414<J(p)<0.91837$ is the constant appearing in\nEllenberg and Gijswijt's bound on arithmetic progression-free subsets of\n$\\mathbb{F}_{p}^{n}$. For large $n$, and $p>3$, this is the first exponential\nimprovement to the trivial bound. We also provide a near optimal result\nconditional on the conjecture that $\\left(\\mathbb{Z}/k\\mathbb{Z}\\right)^{n}$\nsatisfies property $D$, showing that in this case \\[\n\\mathfrak{s}\\left(\\left(\\mathbb{Z}/k\\mathbb{Z}\\right)^{n}\\right)\\leq(k-1)4^{n}+k.\n\\]\n",
"title": "Exponential Bounds for the Erdős-Ginzburg-Ziv Constant"
} | null | null | null | null | true | null | 2940 | null | Default | null | null |
null | {
"abstract": " The success of deep learning in numerous application domains created the de-\nsire to run and train them on mobile devices. This however, conflicts with\ntheir computationally, memory and energy intense nature, leading to a growing\ninterest in compression. Recent work by Han et al. (2015a) propose a pipeline\nthat involves retraining, pruning and quantization of neural network weights,\nobtaining state-of-the-art compression rates. In this paper, we show that\ncompetitive compression rates can be achieved by using a version of soft\nweight-sharing (Nowlan & Hinton, 1992). Our method achieves both quantization\nand pruning in one simple (re-)training procedure. This point of view also\nexposes the relation between compression and the minimum description length\n(MDL) principle.\n",
"title": "Soft Weight-Sharing for Neural Network Compression"
} | null | null | null | null | true | null | 2941 | null | Default | null | null |
null | {
"abstract": " We show that discourse structure, as defined by Rhetorical Structure Theory\nand provided by an existing discourse parser, benefits text categorization. Our\napproach uses a recursive neural network and a newly proposed attention\nmechanism to compute a representation of the text that focuses on salient\ncontent, from the perspective of both RST and the task. Experiments consider\nvariants of the approach and illustrate its strengths and weaknesses.\n",
"title": "Neural Discourse Structure for Text Categorization"
} | null | null | null | null | true | null | 2942 | null | Default | null | null |
null | {
"abstract": " Grid based binary holography (GBH) is an attractive method for patterning\nwith light or matter waves. It is an approximate technique in which different\nholographic masks can be used to produce similar patterns. Here we present an\noptimal design method for GBH masks that allows for freely selecting the\nfraction of open holes in the mask from below 10% to above 90%. Open-fraction\nis an important design parameter when making masks for use in lithography\nsystems. The method also includes a rescaling feature that potentially enables\na better contrast of the generated patterns. Through simulations we investigate\nthe contrast and robustness of the patterns formed by masks generated by the\nproposed optimal design method. It is demonstrated that high contrast patterns\nare achievable for a wide range of open-fractions. We conclude that reaching a\ndesired open-fraction is a trade-off with the contrast of the pattern generated\nby the mask.\n",
"title": "On the optimal design of grid-based binary holograms for matter wave lithography"
} | null | null | [
"Physics"
]
| null | true | null | 2943 | null | Validated | null | null |
null | {
"abstract": " We present spatially and spectrally-resolved observations of CH$_3$OH\nemission from comet C/2012 K1 (PanSTARRS) using The Atacama Large\nMillimeter/submillimeter Array (ALMA) on 2014 June 28-29. Two-dimensional maps\nof the line-of-sight average rotational temperature ($T_{rot}$) were derived,\ncovering spatial scales $0.3''-1.8''$ (corresponding to sky-projected distances\n$\\rho\\sim500$-2500 km). The CH$_3$OH column density distributions are\nconsistent with isotropic, uniform outflow from the nucleus, with no evidence\nfor extended sources of CH$_3$OH in the coma. The $T_{rot}(\\rho)$ radial\nprofiles show a significant drop within a few thousand kilometers of the\nnucleus, falling from about 60 K to 20 K between $\\rho=0$ and 2500 km on June\n28, whereas on June 29, $T_{rot}$ fell from about 120 K to 40 K between $\\rho=$\n0 km and 1000 km. The observed $T_{rot}$ behavior is interpreted primarily as a\nresult of variations in the coma kinetic temperature due to adiabatic cooling\nof the outflowing gas, as well as radiative cooling of the CH$_3$OH rotational\nlevels. Our excitation model shows that radiative cooling is more important for\nthe $J=7-6$ transitions (at 338 GHz) than for the $K=3-2$ transitions (at 252\nGHz), resulting in a strongly sub-thermal distribution of levels in the $J=7-6$\nband at $\\rho\\gtrsim1000$ km. For both bands, the observed temperature drop\nwith distance is less steep than predicted by standard coma theoretical models,\nwhich suggests the presence of a significant source of heating in addition to\nthe photolytic heat sources usually considered.\n",
"title": "Thermal physics of the inner coma: ALMA studies of the methanol distribution and excitation in comet C/2012 K1 (PanSTARRS)"
} | null | null | null | null | true | null | 2944 | null | Default | null | null |
null | {
"abstract": " Nowadays, the availability of large-scale data in disparate application\ndomains urges the deployment of sophisticated tools for extracting valuable\nknowledge out of this huge bulk of information. In that vein, low-rank\nrepresentations (LRRs) which seek low-dimensional embeddings of data have\nnaturally appeared. In an effort to reduce computational complexity and improve\nestimation performance, LRR has been viewed via a matrix factorization (MF)\nperspective. Recently, low-rank MF (LRMF) approaches have been proposed for\ntackling the inherent weakness of MF i.e., the unawareness of the dimension of\nthe low-dimensional space where data reside. Herein, inspired by the merits of\niterative reweighted schemes for rank minimization, we come up with a generic\nlow-rank promoting regularization function. Then, focusing on a specific\ninstance of it, we propose a regularizer that imposes column-sparsity jointly\non the two matrix factors that result from MF, thus promoting low-rankness on\nthe optimization problem. The problems of denoising, matrix completion and\nnon-negative matrix factorization (NMF) are redefined according to the new LRMF\nformulation and solved via efficient Newton-type algorithms with proven\ntheoretical guarantees as to their convergence and rates of convergence to\nstationary points. The effectiveness of the proposed algorithms is verified in\ndiverse simulated and real data experiments.\n",
"title": "Alternating Iteratively Reweighted Minimization Algorithms for Low-Rank Matrix Factorization"
} | null | null | null | null | true | null | 2945 | null | Default | null | null |
null | {
"abstract": " We present a homogeneous set of accurate atmospheric parameters for a\ncomplete sample of very and extremely metal-poor stars in the dwarf spheroidal\ngalaxies (dSphs) Sculptor, Ursa Minor, Sextans, Fornax, Boötes I, Ursa Major\nII, and Leo IV. We also deliver a Milky Way (MW) comparison sample of giant\nstars covering the -4 < [Fe/H] < -1.7 metallicity range. We show that, in the\n[Fe/H] > -3.5 regime, the non-local thermodynamic equilibrium (NLTE)\ncalculations with non-spectroscopic effective temperature (Teff) and surface\ngravity (log~g) based on the photometric methods and known distance provide\nconsistent abundances of the Fe I and Fe II lines. This justifies the Fe I/Fe\nII ionisation equilibrium method to determine log g for the MW halo giants with\nunknown distance. The atmospheric parameters of the dSphs and MW stars were\nchecked with independent methods. In the [Fe/H] > -3.5 regime, the Ti I/Ti II\nionisation equilibrium is fulfilled in the NLTE calculations. In the log~g -\nTeff plane, all the stars sit on the giant branch of the evolutionary tracks\ncorresponding to [Fe/H] = -2 to -4, in line with their metallicities. For some\nof the most metal-poor stars of our sample, we hardly achieve consistent NLTE\nabundances from the two ionisation stages for both iron and titanium. We\nsuggest that this is a consequence of the uncertainty in the Teff-colour\nrelation at those metallicities. The results of these work provide the base for\na detailed abundance analysis presented in a companion paper.\n",
"title": "The formation of the Milky Way halo and its dwarf satellites, a NLTE-1D abundance analysis. I. Homogeneous set of atmospheric parameters"
} | null | null | [
"Physics"
]
| null | true | null | 2946 | null | Validated | null | null |
null | {
"abstract": " A procedure for the design of fixed-gain tracking filters, using an\naugmented-state observer with signal and interference subspaces, is proposed.\nThe signal subspace incorporates an integrating Newtonian model and a\nsecond-order maneuver model that is matched to a sustained constant-g turn; the\ndeterministic interference model creates a Nyquist null for smoother track\nestimates. The selected models provide a simple means of shaping and analyzing\nthe (transient and steady-state) response of tracking-filters of elevated\norder.\n",
"title": "Fixed-Gain Augmented-State Tracking-Filters"
} | null | null | null | null | true | null | 2947 | null | Default | null | null |
null | {
"abstract": " Magnetically active stars possess stellar winds whose interaction with\nplanetary magnetic fields produces radio auroral emission. We examine the\ndetectability of radio auroral emission from Proxima b, the closest known\nexosolar planet orbiting our nearest neighboring star, Proxima Centauri. Using\nthe Radiometric Bode's Law, we estimate the radio flux produced by the\ninteraction of Proxima Centauri's stellar wind and Proxima b's magnetosphere\nfor different planetary magnetic field strengths. For plausible planetary\nmasses, Proxima b produces 6-83 mJy of auroral radio flux at frequencies of\n0.3-0.8 MHz for planetary magnetic field strengths of 1-3 B$_{\\oplus}$.\nAccording to recent MHD models that vary the orbital parameters of the system,\nthis emission is expected to be highly variable. This variability is due to\nlarge fluctuations in the size of Proxima b's magnetosphere as it crosses the\nequatorial streamer regions of the dense stellar wind and high dynamic\npressure. Using the MHD model of Garraffo et al. 2016 for the variation of the\nmagnetosphere radius during the orbit, we estimate that the observed radio flux\ncan vary nearly by an order of magnitude over the 11.2 day period of Proxima b.\nThe detailed amplitude variation depends on the stellar wind, orbital, and\nplanetary magnetic field parameters. We discuss observing strategies for\nproposed future space-based observatories to reach frequencies below the\nionospheric cut off ($\\sim 10$ MHz) as would be required to detect the signal\nwe investigate.\n",
"title": "The Detectability of Radio Auroral Emission from Proxima B"
} | null | null | [
"Physics"
]
| null | true | null | 2948 | null | Validated | null | null |
null | {
"abstract": " We report the electronic band structures and concomitant Fermi surfaces for a\nfamily of exfoliable tetradymite compounds with the formula $T_2$$Ch_2$$Pn$,\nobtained as a modification to the well-known topological insulator binaries\nBi$_2$(Se,Te)$_3$ by replacing one chalcogen ($Ch$) with a pnictogen ($Pn$) and\nBi with the tetravalent transition metals $T$ $=$ Ti, Zr, or Hf. This\nimbalances the electron count and results in layered metals characterized by\nrelatively high carrier mobilities and bulk two-dimensional Fermi surfaces\nwhose topography is well-described by first principles calculations.\nIntriguingly, slab electronic structure calculations predict Dirac-like surface\nstates. In contrast to Bi$_2$Se$_3$, where the surface Dirac bands are at the\n$\\Gamma-$point, for (Zr,Hf)$_2$Te$_2$(P,As) there are Dirac cones of strong\ntopological character around both the $\\bar {\\Gamma}$- and $\\bar {M}$-points\nwhich are above and below the Fermi energy, respectively. For Ti$_2$Te$_2$P the\nsurface state is predicted to exist only around the $\\bar {M}$-point. In\nagreement with these predictions, the surface states that are located below the\nFermi energy are observed by angle resolved photoemission spectroscopy\nmeasurements, revealing that they coexist with the bulk metallic state. Thus,\nthis family of materials provides a foundation upon which to develop novel\nphenomena that exploit both the bulk and surface states (e.g., topological\nsuperconductivity).\n",
"title": "Converting topological insulators into topological metals within the tetradymite family"
} | null | null | null | null | true | null | 2949 | null | Default | null | null |
null | {
"abstract": " Given a set of data, one central goal is to group them into clusters based on\nsome notion of similarity between the individual objects. One of the most\npopular and widely-used approaches is k-means despite the computational\nhardness to find its global minimum. We study and compare the properties of\ndifferent convex relaxations by relating them to corresponding proximity\nconditions, an idea originally introduced by Kumar and Kannan. Using conic\nduality theory, we present an improved proximity condition under which the\nPeng-Wei relaxation of k-means recovers the underlying clusters exactly. Our\nproximity condition improves upon Kumar and Kannan, and is comparable to that\nof Awashti and Sheffet where proximity conditions are established for\nprojective k-means. In addition, we provide a necessary proximity condition for\nthe exactness of the Peng-Wei relaxation. For the special case of equal cluster\nsizes, we establish a different and completely localized proximity condition\nunder which the Amini-Levina relaxation yields exact clustering, thereby having\naddressed an open problem by Awasthi and Sheffet in the balanced case. Our\nframework is not only deterministic and model-free but also comes with a clear\ngeometric meaning which allows for further analysis and generalization.\nMoreover, it can be conveniently applied to analyzing various data generative\nmodels such as the stochastic ball models and Gaussian mixture models. With\nthis method, we improve the current minimum separation bound for the stochastic\nball models and achieve the state-of-the-art results of learning Gaussian\nmixture models.\n",
"title": "When Do Birds of a Feather Flock Together? k-Means, Proximity, and Conic Programming"
} | null | null | [
"Mathematics"
]
| null | true | null | 2950 | null | Validated | null | null |
null | {
"abstract": " Active particles, which interact hydrodynamically, display a remarkable\nvariety of emergent collective phenomena. We use squirmers to model spherical\nmicroswimmers and explore the collective behavior of thousands of them under\nthe influence of strong gravity using the method of multi-particle collision\ndynamics for simulating fluid flow. The sedimentation profile depends on the\nratio of swimming to sedimentation velocity as well as on the squirmer type. It\nshows close packed squirmer layers at the bottom and a highly dynamic region\nwith exponential density dependence towards the top. The mean vertical\norientation of the squirmers strongly depends on height. For swimming\nvelocities larger than the sedimentation velocity, squirmers show strong\nconvection in the exponential region. We quantify the strength of convection\nand the extent of convection cells by the vertical current density and its\ncurrent dipole, which are large for neutral squirmers as well as for weak\npushers and pullers.\n",
"title": "Collective Sedimentation of Squirmers under Gravity"
} | null | null | null | null | true | null | 2951 | null | Default | null | null |
null | {
"abstract": " Many applications of machine learning, for example in health care, would\nbenefit from methods that can guarantee privacy of data subjects. Differential\nprivacy (DP) has become established as a standard for protecting learning\nresults. The standard DP algorithms require a single trusted party to have\naccess to the entire data, which is a clear weakness. We consider DP Bayesian\nlearning in a distributed setting, where each party only holds a single sample\nor a few samples of the data. We propose a learning strategy based on a secure\nmulti-party sum function for aggregating summaries from data holders and the\nGaussian mechanism for DP. Our method builds on an asymptotically optimal and\npractically efficient DP Bayesian inference with rapidly diminishing extra\ncost.\n",
"title": "Differentially Private Bayesian Learning on Distributed Data"
} | null | null | null | null | true | null | 2952 | null | Default | null | null |
null | {
"abstract": " We experimentally study the stability of a bosonic Mott-insulator against the\nformation of a density wave induced by long-range interactions, and\ncharacterize the intrinsic dynamics between these two states. The\nMott-insulator is created in a quantum degenerate gas of 87-Rubidium atoms,\ntrapped in a three-dimensional optical lattice. The gas is located inside and\nglobally coupled to an optical cavity. This causes interactions of global\nrange, mediated by photons dispersively scattered between a transverse lattice\nand the cavity. The scattering comes with an atomic density modulation, which\nis measured by the photon flux leaking from the cavity. We initialize the\nsystem in a Mott-insulating state and then rapidly increase the global coupling\nstrength. We observe that the system falls into either of two distinct final\nstates. One is characterized by a low photon flux, signaling a Mott insulator,\nand the other is characterized by a high photon flux, which we associate with a\ndensity wave. Ramping the global coupling slowly, we observe a hysteresis loop\nbetween the two states - a further signature of metastability. A comparison\nwith a theoretical model confirms that the metastability originates in the\ncompetition between short- and global-range interactions. From the increasing\nphoton flux monitored during the switching process, we find that several\nthousand atoms tunnel to a neighboring site on the time scale of the single\nparticle dynamics. We argue that a density modulation, initially forming in the\ncompressible surface of the trapped gas, triggers an avalanche tunneling\nprocess in the Mott-insulating region.\n",
"title": "Metastability and avalanche dynamics in strongly-correlated gases with long-range interactions"
} | null | null | null | null | true | null | 2953 | null | Default | null | null |
null | {
"abstract": " We present a scheme for nanoscopic imaging of a quantum mechanical two-level\nsystem using an optical probe in the far-field. Existing super-resolution\nschemes require more than two-levels and depend on an incoherent response to\nthe lasers. Here, quantum control of the two states proceeds via rapid\nadiabatic passage. We implement this scheme on an array of semiconductor\nself-assembled quantum dots. Each quantum dot results in a bright spot in the\nimage with extents down to 30 nm ({\\lambda}/31). Rapid adiabatic passage is\nestablished as a versatile tool in the super-resolution toolbox.\n",
"title": "Optical nanoscopy via quantum control"
} | null | null | null | null | true | null | 2954 | null | Default | null | null |
null | {
"abstract": " We present a deep learning approach to the ISIC 2017 Skin Lesion\nClassification Challenge using a multi-scale convolutional neural network. Our\napproach utilizes an Inception-v3 network pre-trained on the ImageNet dataset,\nwhich is fine-tuned for skin lesion classification using two different scales\nof input images.\n",
"title": "Skin Lesion Classification Using Deep Multi-scale Convolutional Neural Networks"
} | null | null | null | null | true | null | 2955 | null | Default | null | null |
null | {
"abstract": " In nonlinear dynamics, and to a lesser extent in other fields, a widely used\nmeasure of complexity is the Permutation Entropy. But there is still no known\nmethod to determine the accuracy of this measure. There has been little\nresearch on the statistical properties of this quantity that characterize time\nseries. The literature describes some resampling methods of quantities used in\nnonlinear dynamics - as the largest Lyapunov exponent - but all of these seems\nto fail. In this contribution we propose a parametric bootstrap methodology\nusing a symbolic representation of the time series in order to obtain the\ndistribution of the Permutation Entropy estimator. We perform several time\nseries simulations given by well known stochastic processes: the 1=f? noise\nfamily, and show in each case that the proposed accuracy measure is as\nefficient as the one obtained by the frequentist approach of repeating the\nexperiment. The complexity of brain electrical activity, measured by the\nPermutation Entropy, has been extensively used in epilepsy research for\ndetection in dynamical changes in electroencephalogram (EEG) signal with no\nconsideration of the variability of this complexity measure. An application of\nthe parametric bootstrap methodology is used to compare normal and pre-ictal\nEEG signals.\n",
"title": "Confidence Intervals and Hypothesis Testing for the Permutation Entropy with an application to Epilepsy"
} | null | null | null | null | true | null | 2956 | null | Default | null | null |
null | {
"abstract": " The ungrammatical sentence \"The key to the cabinets are on the table\" is\nknown to lead to an illusion of grammaticality. As discussed in the\nmeta-analysis by Jaeger et al., 2017, faster reading times are observed at the\nverb are in the agreement-attraction sentence above compared to the equally\nungrammatical sentence \"The key to the cabinet are on the table\". One\nexplanation for this facilitation effect is the feature percolation account:\nthe plural feature on cabinets percolates up to the head noun key, leading to\nthe illusion. An alternative account is in terms of cue-based retrieval (Lewis\n& Vasishth, 2005), which assumes that the non-subject noun cabinets is\nmisretrieved due to a partial feature-match when a dependency completion\nprocess at the auxiliary initiates a memory access for a subject with plural\nmarking. We present evidence for yet another explanation for the observed\nfacilitation. Because the second sentence has two nouns with identical number,\nit is possible that these are, in some proportion of trials, more difficult to\nkeep distinct, leading to slower reading times at the verb in the first\nsentence above; this is the feature overwriting account of Nairne, 1990. We\nshow that the feature overwriting proposal can be implemented as a finite\nmixture process. We reanalysed ten published data-sets, fitting hierarchical\nBayesian mixture models to these data assuming a two-mixture distribution. We\nshow that in nine out of the ten studies, a mixture distribution corresponding\nto feature overwriting furnishes a superior fit over both the feature\npercolation and the cue-based retrieval accounts.\n",
"title": "Feature overwriting as a finite mixture process: Evidence from comprehension data"
} | null | null | null | null | true | null | 2957 | null | Default | null | null |
null | {
"abstract": " This is a photographic dataset collected for testing image processing\nalgorithms. The idea is to have images that can exploit the properties of total\nvariation, therefore a set of playing cards was distributed on the scene. The\ndataset is made available at www.fips.fi/photographic_dataset2.php\n",
"title": "Photographic dataset: playing cards"
} | null | null | [
"Computer Science",
"Physics"
]
| null | true | null | 2958 | null | Validated | null | null |
null | {
"abstract": " Human learning is a complex process in which future behavior is altered via\nthe modulation of neural activity. Yet, the degree to which brain activity and\nfunctional connectivity during learning is constrained across subjects, for\nexample by conserved anatomy and physiology or by the nature of the task,\nremains unknown. Here, we measured brain activity and functional connectivity\nin a longitudinal experiment in which healthy adult human participants learned\nthe values of novel objects over the course of four days. We assessed the\npresence of constraints on activity and functional connectivity using an\ninter-subject correlation approach. Constraints on activity and connectivity\nwere greater in magnitude than expected in a non-parametric permutation-based\nnull model, particularly in primary sensory and motor systems, as well as in\nregions associated with the learning of value. Notably, inter-subject\nconnectivity in activity and connectivity displayed marked temporal variations,\nwith inter-subject correlations in activity exceeding those in connectivity\nduring early learning and \\emph{visa versa} in later learning. Finally,\nindividual differences in performance accuracy tracked the degree to which a\nsubject's connectivity, but not activity, tracked subject-general patterns.\nTaken together, our results support the notion that brain activity and\nconnectivity are constrained across subjects in early learning, with\nconstraints on activity, but not connectivity, decreasing in later learning.\n",
"title": "Dynamic constraints on activity and connectivity during the learning of value"
} | null | null | null | null | true | null | 2959 | null | Default | null | null |
null | {
"abstract": " We follow the dual approach to Coxeter systems and show for Weyl groups a\ncriterium which decides whether a set of reflections is generating the group\ndepending on the root and the coroot lattice. Further we study special\ngenerating sets involving a parabolic subgroup and show that they are very\ntame.\n",
"title": "A note on Weyl groups and crystallographic root lattices"
} | null | null | null | null | true | null | 2960 | null | Default | null | null |
null | {
"abstract": " In the emerging advancement in the branch of autonomous robotics, the ability\nof a robot to efficiently localize and construct maps of its surrounding is\ncrucial. This paper deals with utilizing thermal-infrared cameras, as opposed\nto conventional cameras as the primary sensor to capture images of the robot's\nsurroundings. For localization, the images need to be further processed before\nfeeding them to a navigational system. The main motivation of this paper was to\ndevelop an edge detection methodology capable of utilizing the low-SNR poor\noutput from such a thermal camera and effectively detect smooth edges of the\nsurrounding environment. The enhanced edge detector proposed in this paper\ntakes the raw image from the thermal sensor, denoises the images, applies Canny\nedge detection followed by CSS method. The edges are ranked to remove any noise\nand only edges of the highest rank are kept. Then, the broken edges are linked\nby computing edge metrics and a smooth edge of the surrounding is displayed in\na binary image. Several comparisons are also made in the paper between the\nproposed technique and the existing techniques.\n",
"title": "Smoothness-based Edge Detection using Low-SNR Camera for Robot Navigation"
} | null | null | null | null | true | null | 2961 | null | Default | null | null |
null | {
"abstract": " Game theory has emerged as a novel approach for the coordination of\nmultiagent systems. A fundamental component of this approach is the design of a\nlocal utility function for each agent so that their selfish maximization\nachieves the global objective. In this paper we propose a novel framework to\ncharacterize and optimize the worst case performance (price of anarchy) of any\nresulting equilibrium as a function of the chosen utilities, thus providing a\nperformance certificate for a large class of algorithms. More specifically, we\nconsider a class of resource allocation problems, where each agent selects a\nsubset of the resources with the goal of maximizing a welfare function. First,\nwe show that any smoothness argument is inconclusive for the design problems\nconsidered. Motivated by this, we introduce a new approach providing a tight\nexpression for the price of anarchy (PoA) as a function of the chosen utility\nfunctions. Leveraging this result, we show how to design the utilities so as to\nmaximize the PoA through a tractable linear program. In Part II we specialize\nthe results to submodular and supermodular welfare functions, discuss\ncomplexity issues and provide two applications.\n",
"title": "Distributed resource allocation through utility design - Part I: optimizing the performance certificates via the price of anarchy"
} | null | null | null | null | true | null | 2962 | null | Default | null | null |
null | {
"abstract": " Advances in deep learning have led to substantial increases in prediction\naccuracy but have been accompanied by increases in the cost of rendering\npredictions. We conjecture that fora majority of real-world inputs, the recent\nadvances in deep learning have created models that effectively \"overthink\" on\nsimple inputs. In this paper, we revisit the classic question of building model\ncascades that primarily leverage class asymmetry to reduce cost. We introduce\nthe \"I Don't Know\"(IDK) prediction cascades framework, a general framework to\nsystematically compose a set of pre-trained models to accelerate inference\nwithout a loss in prediction accuracy. We propose two search based methods for\nconstructing cascades as well as a new cost-aware objective within this\nframework. The proposed IDK cascade framework can be easily adopted in the\nexisting model serving systems without additional model re-training. We\nevaluate the proposed techniques on a range of benchmarks to demonstrate the\neffectiveness of the proposed framework.\n",
"title": "IDK Cascades: Fast Deep Learning by Learning not to Overthink"
} | null | null | null | null | true | null | 2963 | null | Default | null | null |
null | {
"abstract": " Being able to fall safely is a necessary motor skill for humanoids performing\nhighly dynamic tasks, such as running and jumping. We propose a new method to\nlearn a policy that minimizes the maximal impulse during the fall. The\noptimization solves for both a discrete contact planning problem and a\ncontinuous optimal control problem. Once trained, the policy can compute the\noptimal next contacting body part (e.g. left foot, right foot, or hands),\ncontact location and timing, and the required joint actuation. We represent the\npolicy as a mixture of actor-critic neural network, which consists of n control\npolicies and the corresponding value functions. Each pair of actor-critic is\nassociated with one of the n possible contacting body parts. During execution,\nthe policy corresponding to the highest value function will be executed while\nthe associated body part will be the next contact with the ground. With this\nmixture of actor-critic architecture, the discrete contact sequence planning is\nsolved through the selection of the best critics while the continuous control\nproblem is solved by the optimization of actors. We show that our policy can\nachieve comparable, sometimes even higher, rewards than a recursive search of\nthe action space using dynamic programming, while enjoying 50 to 400 times of\nspeed gain during online execution.\n",
"title": "Learning a Unified Control Policy for Safe Falling"
} | null | null | null | null | true | null | 2964 | null | Default | null | null |
null | {
"abstract": " The collisional shift of a transition constitutes an important systematic\neffect in high-precision spectroscopy. Accurate values for van der\nWaalsinteraction coefficients are required in order to evaluate the\ndistance-dependent frequency shift. We here consider the interaction of excited\nhydrogen 6P atoms with metastable atoms (in the 2S state), in order to explore\nthe influence of quasi-degenerate 2P, and 6S states on the dipole-dipole\ninteraction. The motivation for the calculation is given by planned\nhigh-precision measurements of the transition. Due to the presence of\nquasi-degenerate levels, one can use the non-retarded approximation for the\ninteraction terms over wide distance ranges.\n",
"title": "Long-Range Interactions for Hydrogen: 6P-1S and 6P-2S"
} | null | null | null | null | true | null | 2965 | null | Default | null | null |
null | {
"abstract": " Generating music medleys is about finding an optimal permutation of a given\nset of music clips. Toward this goal, we propose a self-supervised learning\ntask, called the music puzzle game, to train neural network models to learn the\nsequential patterns in music. In essence, such a game requires machines to\ncorrectly sort a few multisecond music fragments. In the training stage, we\nlearn the model by sampling multiple non-overlapping fragment pairs from the\nsame songs and seeking to predict whether a given pair is consecutive and is in\nthe correct chronological order. For testing, we design a number of puzzle\ngames with different difficulty levels, the most difficult one being music\nmedley, which requiring sorting fragments from different songs. On the basis of\nstate-of-the-art Siamese convolutional network, we propose an improved\narchitecture that learns to embed frame-level similarity scores computed from\nthe input fragment pairs to a common space, where fragment pairs in the correct\norder can be more easily identified. Our result shows that the resulting model,\ndubbed as the similarity embedding network (SEN), performs better than\ncompeting models across different games, including music jigsaw puzzle, music\nsequencing, and music medley. Example results can be found at our project\nwebsite, this https URL.\n",
"title": "Generating Music Medleys via Playing Music Puzzle Games"
} | null | null | null | null | true | null | 2966 | null | Default | null | null |
null | {
"abstract": " We investigate the focusing coupled PT-symmetric nonlocal nonlinear\nSchrodinger equation employing Darboux transformation approach. We find a\nfamily of exact solutions including pairs of Bright-Bright, Dark-Dark and\nBright-Dark solitons in addition to solitary waves. We show that one can\nconvert bright bound state onto a dark bound state in a two-soliton solution by\nselectively fine tuning the amplitude dependent parameter. We also show that\nthe energy in each mode remains conserved unlike the celebrated Manakov model.\nWe also characterize the behaviour of the soliton solutions in detail. We\nemphasize that the above phenomenon occurs due to the nonlocality of the model.\n",
"title": "Collisional Dynamics of Solitons in the Coupled PT symmetric Nonlocal nonlinear Schrodinger equations"
} | null | null | null | null | true | null | 2967 | null | Default | null | null |
null | {
"abstract": " We have performed magnetic susceptibility, heat capacity, muon spin\nrelaxation, and neutron scattering measurements on three members of the family\nBa3MRu2O9, where M = In, Y and Lu. These systems consist of mixed-valence Ru\ndimers on a triangular lattice with antiferromagnetic interdimer exchange.\nAlthough previous work has argued that charge order within the dimers or\nintradimer double exchange plays an important role in determining the magnetic\nproperties, our results suggest that the dimers are better described as\nmolecular units due to significant orbital hybridization, resulting in one\nspin-1/2 moment distributed equally over the two Ru sites. These molecular\nbuilding blocks form a frustrated, quasi-two-dimensional triangular lattice.\nOur zero and longitudinal field muSR results indicate that the molecular\nmoments develop a collective, static magnetic ground state, with oscillations\nof the zero field muon spin polarization indicative of long-range magnetic\norder in the Lu sample. The static magnetism is much more disordered in the Y\nand In samples, but they do not appear to be conventional spin glasses.\n",
"title": "Frustrated spin-1/2 molecular magnetism in the mixed-valence antiferromagnets Ba3MRu2O9 (M = In, Y, Lu)"
} | null | null | [
"Physics"
]
| null | true | null | 2968 | null | Validated | null | null |
null | {
"abstract": " The goal of this paper is to present an end-to-end, data-driven framework to\ncontrol Autonomous Mobility-on-Demand systems (AMoD, i.e. fleets of\nself-driving vehicles). We first model the AMoD system using a time-expanded\nnetwork, and present a formulation that computes the optimal rebalancing\nstrategy (i.e., preemptive repositioning) and the minimum feasible fleet size\nfor a given travel demand. Then, we adapt this formulation to devise a Model\nPredictive Control (MPC) algorithm that leverages short-term demand forecasts\nbased on historical data to compute rebalancing strategies. We test the\nend-to-end performance of this controller with a state-of-the-art LSTM neural\nnetwork to predict customer demand and real customer data from DiDi Chuxing: we\nshow that this approach scales very well for large systems (indeed, the\ncomputational complexity of the MPC algorithm does not depend on the number of\ncustomers and of vehicles in the system) and outperforms state-of-the-art\nrebalancing strategies by reducing the mean customer wait time by up to to\n89.6%.\n",
"title": "Data-Driven Model Predictive Control of Autonomous Mobility-on-Demand Systems"
} | null | null | null | null | true | null | 2969 | null | Default | null | null |
null | {
"abstract": " The SPIRou near infrared spectro-polarimeter is destined to begin science\noperations at the Canada-France-Hawaii Telescope in mid-2018. One of the\ninstrument's primary science goals is to discover the closest exoplanets to the\nSolar System by conducting a 3-5 year long radial velocity survey of nearby M\ndwarfs at an expected precision of $\\sim 1$ m s$^{-1}$; the SPIRou Legacy\nSurvey-Planet Search (SLS-PS). In this study we conduct a detailed Monte-Carlo\nsimulation of the SLS-PS using our current understanding of the occurrence rate\nof M dwarf planetary systems and physical models of stellar activity. From\nsimultaneous modelling of planetary signals and activity, we predict the\npopulation of planets detected in the SLS-PS. With our fiducial survey strategy\nand expected instrument performance over a nominal survey length of $\\sim 3$\nyears, we expect SPIRou to detect $85.3^{+29.3}_{-12.4}$ planets including\n$20.0^{+16.8}_{-7.2}$ habitable zone planets and $8.1^{+7.6}_{-3.2}$ Earth-like\nplanets from a sample of 100 M1-M8.5 dwarfs out to 11 pc. By studying\nmid-to-late M dwarfs previously inaccessible to existing optical velocimeters,\nSPIRou will put meaningful constraints on the occurrence rate of planets around\nthose stars including the value of $\\eta_{\\oplus}$ at an expected level of\nprecision of $\\lesssim 45$%. We also predict a subset of $46.7^{+16.0}_{-6.0}$\nplanets may be accessible with dedicated high-contrast imagers on the next\ngeneration of ELTs including $4.9^{+4.7}_{-2.0}$ potentially imagable\nEarth-like planets. Lastly, we compare the results of our fiducial survey\nstrategy to other foreseeable survey versions to quantify which strategy is\noptimized to reach the SLS-PS science goals. The results of our simulations are\nmade available to the community on github.\n",
"title": "Predictions of planet detections with near infrared radial velocities in the up-coming SPIRou Legacy Survey-Planet Search"
} | null | null | null | null | true | null | 2970 | null | Default | null | null |
null | {
"abstract": " We construct energy-dependent potentials for which the Schroedinger equations\nadmit solu- tions in terms of exceptional orthogonal polynomials. Our method of\nconstruction is based on certain point transformations, applied to the\nequations of exceptional Hermite, Jacobi and Laguerre polynomials. We present\nseveral examples of boundary-value problems with energy-dependent potentials\nthat admit a discrete spectrum and the corresponding normalizable solutions in\nclosed form.\n",
"title": "Quantum models with energy-dependent potentials solvable in terms of exceptional orthogonal polynomials"
} | null | null | null | null | true | null | 2971 | null | Default | null | null |
null | {
"abstract": " This paper is intended both an introduction to the algebraic geometry of\nholomorphic Poisson brackets, and as a survey of results on the classification\nof projective Poisson manifolds that have been obtained in the past twenty\nyears. It is based on the lecture series delivered by the author at the Poisson\n2016 Summer School in Geneva. The paper begins with a detailed treatment of\nPoisson surfaces, including adjunction, ruled surfaces and blowups, and leading\nto a statement of the full birational classification. We then describe several\nconstructions of Poisson threefolds, outlining the classification in the\nregular case, and the case of rank-one Fano threefolds (such as projective\nspace). Following a brief introduction to the notion of Poisson subspaces, we\ndiscuss Bondal's conjecture on the dimensions of degeneracy loci on Poisson\nFano manifolds. We close with a discussion of log symplectic manifolds with\nsimple normal crossings degeneracy divisor, including a new proof of the\nclassification in the case of rank-one Fano manifolds.\n",
"title": "Constructions and classifications of projective Poisson varieties"
} | null | null | null | null | true | null | 2972 | null | Default | null | null |
null | {
"abstract": " The principle of the common cause claims that if an improbable coincidence\nhas occurred, there must exist a common cause. This is generally taken to mean\nthat positive correlations between non-causally related events should disappear\nwhen conditioning on the action of some underlying common cause. The extended\ninterpretation of the principle, by contrast, urges that common causes should\nbe called for in order to explain positive deviations between the estimated\ncorrelation of two events and the expected value of their correlation. The aim\nof this paper is to provide the extended reading of the principle with a\ngeneral probabilistic model, capturing the simultaneous action of a system of\nmultiple common causes. To this end, two distinct models are elaborated, and\nthe necessary and sufficient conditions for their existence are determined.\n",
"title": "Generalised Reichenbachian Common Cause Systems"
} | null | null | null | null | true | null | 2973 | null | Default | null | null |
null | {
"abstract": " We report the discovery and analysis of the most metal-poor damped\nLyman-alpha (DLA) system currently known, based on observations made with the\nKeck HIRES spectrograph. The metal paucity of this system has only permitted\nthe determination of three element abundances: [C/H] = -3.43 +/- 0.06, [O/H] =\n-3.05 +/- 0.05, and [Si/H] = -3.21 +/- 0.05, as well as an upper limit on the\nabundance of iron: [Fe/H] < -2.81. This DLA is among the most carbon-poor\nenvironment currently known with detectable metals. By comparing the abundance\npattern of this DLA to detailed models of metal-free nucleosynthesis, we find\nthat the chemistry of the gas is consistent with the yields of a 20.5 M_sun\nmetal-free star that ended its life as a core-collapse supernova; the\nabundances we measure are inconsistent with the yields of pair-instability\nsupernovae. Such a tight constraint on the mass of the progenitor Population\nIII star is afforded by the well-determined C/O ratio, which we show depends\nalmost monotonically on the progenitor mass when the kinetic energy of the\nsupernova explosion is E_exp > 1.5x10^51 erg. We find that the DLA presented\nhere has just crossed the critical 'transition discriminant' threshold,\nrendering the DLA gas now suitable for low mass star formation. We also discuss\nthe chemistry of this system in the context of recent models that suggest some\nof the most metal-poor DLAs are the precursors of the 'first galaxies', and are\nthe antecedents of the ultra-faint dwarf galaxies.\n",
"title": "Discovery of the most metal-poor damped Lyman-alpha system"
} | null | null | null | null | true | null | 2974 | null | Default | null | null |
null | {
"abstract": " In this paper, we explore remarkable similarities between multi-transactional\nbehaviors of smart contracts in cryptocurrencies such as Ethereum and classical\nproblems of shared-memory concurrency. We examine two real-world examples from\nthe Ethereum blockchain and analyzing how they are vulnerable to bugs that are\nclosely reminiscent to those that often occur in traditional concurrent\nprograms. We then elaborate on the relation between observable contract\nbehaviors and well-studied concurrency topics, such as atomicity, interference,\nsynchronization, and resource ownership. The described\ncontracts-as-concurrent-objects analogy provides deeper understanding of\npotential threats for smart contracts, indicate better engineering practices,\nand enable applications of existing state-of-the-art formal verification\ntechniques.\n",
"title": "A Concurrent Perspective on Smart Contracts"
} | null | null | null | null | true | null | 2975 | null | Default | null | null |
null | {
"abstract": " Existing works on building a soliton transmission system only encode\ninformation using the imaginary part of the eigenvalue, which fails to make\nfull use of the signal degree-of-freedoms. Motivated by this observation, we\nmake the first step of encoding information using (discrete) spectral\namplitudes by proposing analytical noise models for the spectral amplitudes of\n$N$-solitons ($N\\geq 1$). To our best knowledge, this is the first work in\nbuilding an analytical noise model for spectral amplitudes, which leads to many\ninteresting information theoretic questions, such as channel capacity analysis,\nand has a potential of increasing the transmission rate. The noise statistics\nof the spectral amplitude of a soliton are also obtained without the Gaussian\napproximation.\n",
"title": "Noise Models in the Nonlinear Spectral Domain for Optical Fibre Communications"
} | null | null | null | null | true | null | 2976 | null | Default | null | null |
null | {
"abstract": " In this paper we are concerned with the approach to shape analysis based on\nthe so called Square Root Velocity Transform (SRVT). We propose a\ngeneralisation of the SRVT from Euclidean spaces to shape spaces of curves on\nLie groups and on homogeneous manifolds. The main idea behind our approach is\nto exploit the geometry of the natural Lie group actions on these spaces.\n",
"title": "Shape analysis on Lie groups and homogeneous spaces"
} | null | null | null | null | true | null | 2977 | null | Default | null | null |
null | {
"abstract": " Health economic evaluation studies are widely used in public health to assess\nhealth strategies in terms of their cost-effectiveness and inform public\npolicies. We developed an R package for Markov models implementing most of the\nmodelling and reporting features described in reference textbooks and\nguidelines: deterministic and probabilistic sensitivity analysis, heterogeneity\nanalysis, time dependency on state-time and model-time (semi-Markov and\nnon-homogeneous Markov models), etc. In this paper we illustrate the features\nof heemod by building and analysing an example Markov model. We then explain\nthe design and the underlying implementation of the package.\n",
"title": "Markov Models for Health Economic Evaluations: The R Package heemod"
} | null | null | null | null | true | null | 2978 | null | Default | null | null |
null | {
"abstract": " Today freshwater is more important than ever before and it is contaminated\nfrom textile industry. Removal of dyes from effluent of textile using amorphous\nalloys has been studied extensively by many researchers. In this review article\nit is presented up to date development on the azo dye degradation performance\nof amorphous alloys, a new class of catalytic materials. Numerous amorphous\nalloys have been developed for increasing higher degradation efficiency in\ncomparison to conventional ones for the removal of azo dyes in wastewater. One\nof the objectives of this review article is to organize the scattered available\ninformation on various aspects on a wide range of potentially effective in the\nremoval of dyes by using amorphous alloys. This study comprises the affective\nremoval factors of azo dye such as solution pH, initial dye concentration, and\nadsorbent dosage. It was concluded that Fe, Mg, Co, Al and Mn-based amorphous\nalloys with wide availability have appreciable for removing several types of\nazo dyes from wastewater. Concerning amorphous alloys for future research, some\nsuggestions are proposed and conclusions have been drawn.\n",
"title": "Amorphous Alloys, Degradation Performance of Azo Dyes: Review"
} | null | null | null | null | true | null | 2979 | null | Default | null | null |
null | {
"abstract": " Despite of the appearance of numerous new materials, the iron based alloys\nand steels continue to play an essential role in modern technology. The\nproperties of a steel are determined by its structural state (ferrite,\ncementite, pearlite, bainite, martensite, and their combination) that is formed\nunder thermal treatment as a result of the shear lattice reconstruction \"gamma\"\n(fcc) -> \"alpha\" (bcc) and carbon diffusion redistribution. We present a review\non a recent progress in the development of a quantitative theory of the phase\ntransformations and microstructure formation in steel that is based on an ab\ninitio parameterization of the Ginzburg-Landau free energy functional. The\nresults of computer modeling describe the regular change of transformation\nscenario under cooling from ferritic (nucleation and diffusion-controlled\ngrowth of the \"alpha\" phase to martensitic (the shear lattice instability\n\"gamma\" -> \"alpha\"). It has been shown that the increase in short-range\nmagnetic order with decreasing the temperature plays a key role in the change\nof transformation scenarios. Phase-field modeling in the framework of a\ndiscussed approach demonstrates the typical transformation patterns.\n",
"title": "Towards the ab initio based theory of the phase transformations in iron and steel"
} | null | null | null | null | true | null | 2980 | null | Default | null | null |
null | {
"abstract": " We study the bulk and surface nonlinear modes of the modified one-dimensional\ndiscrete nonlinear Schroedinger (mDNLS) equation. A linear and a modulational\nstability analysis of the lowest-order modes is carried out. While for the\nfundamental bulk mode there is no power threshold, the fundamental surface mode\nneeds a minimum power level to exist. Examination of the time evolution of\ndiscrete solitons in the limit of strongly localized modes, suggests ways to\nmanage the Peierls- Nabarro barrier, facilitating in this way a degree of\nsteering. The long-time propagation of an initially localized excitation shows\nthat, at long evolution times, nonlinear effects become negligible and as a\nresult, the propagation becomes ballistic. The similarity of all these results\nto the ones obtained for the DNLS equation, points out to the robustness of the\ndiscrete soliton phenomenology.\n",
"title": "Solitons in a modified discrete nonlinear Schroedinger equation"
} | null | null | [
"Physics"
]
| null | true | null | 2981 | null | Validated | null | null |
null | {
"abstract": " A possibility of the topological Kosterlitz-Thouless~(KT) transition in the\nPokrovsky-Talapov~(PT) model is investigated by using the functional\nrenormalization-group (RG) approach by Wetterich. Our main finding is that the\nnonzero misfit parameter of the model, which can be related with the linear\ngradient term (Dzyaloshinsky-Moriya interaction), makes such a transition\nimpossible, what contradicts the previous consideration of this problem by\nnon-perturbative RG methods. To support the conclusion the initial PT model is\nreformulated in terms of the 2D theory of relativistic fermions using an\nanalogy between the 2D sine-Gordon and the massive Thirring models. In the new\nformalism the misfit parameter corresponds to an effective gauge field that\nenables to include it in the RG procedure on an equal footing with the other\nparameters of the theory. The Wetterich equation is applied to obtain flow\nequations for the parameters of the new fermionic action. We demonstrate that\nthese equations reproduce the KT type of behavior if the misfit parameter is\nzero. However, any small nonzero value of the quantity rules out a possibility\nof the KT transition. To confirm the finding we develop a description of the\nproblem in terms of the 2D Coulomb gas model. Within the approach the breakdown\nof the KT scenario gains a transparent meaning, the misfit gives rise to an\neffective in-plane electric field that prevents a formation of bound\nvortex-antivortex pairs.\n",
"title": "Functional renormalization-group approach to the Pokrovsky-Talapov model via modified massive Thirring fermion model"
} | null | null | null | null | true | null | 2982 | null | Default | null | null |
null | {
"abstract": " The short coherence lengths characteristic of low-dimensional superconductors\nare associated with usefully high critical fields or temperatures.\nUnfortunately, such materials are often sensitive to disorder and suffer from\nphase fluctuations in the superconducting order parameter which diverge with\ntemperature $T$, magnetic field $H$ or current $I$. We propose an approach to\novercome synthesis and fluctuation problems: building superconductors from\ninhomogeneous composites of nanofilaments. Macroscopic crystals of\nquasi-one-dimensional Na$_{2-\\delta}$Mo$_6$Se$_6$ featuring Na vacancy disorder\n($\\delta\\approx$~0.2) are shown to behave as percolative networks of\nsuperconducting nanowires. Long range order is established via transverse\ncoupling between individual one-dimensional filaments, yet phase coherence\nremains unstable to fluctuations and localization in the zero-($T$,$H$,$I$)\nlimit. However, a region of reentrant phase coherence develops upon raising\n($T$,$H$,$I$). We attribute this phenomenon to an enhancement of the transverse\ncoupling due to electron delocalization. Our observations of reentrant phase\ncoherence coincide with a peak in the Josephson energy $E_J$ at non-zero\n($T$,$H$,$I$), which we estimate using a simple analytical model for a\ndisordered anisotropic superconductor. Na$_{2-\\delta}$Mo$_6$Se$_6$ is therefore\na blueprint for a future generation of nanofilamentary superconductors with\ninbuilt resilience to phase fluctuations at elevated ($T$,$H$,$I$).\n",
"title": "Reentrant Phase Coherence in Superconducting Nanowire Composites"
} | null | null | null | null | true | null | 2983 | null | Default | null | null |
null | {
"abstract": " In this work we investigate the potential of tetragonal L1$_0$ ordered FeNi\nas candidate phase for rare earth free permanent magnets taking into account\nanisotropy values from recently synthesized, partially ordered FeNi thin films.\nIn particular, we estimate the maximum energy product ($BH$)$_\\mathrm{max}$ of\nL1$_0$-FeNi nanostructures using micromagnetic simulations. The maximum energy\nproduct is limited due to the small coercive field of partially ordered\nL1$_0$-FeNi. Nano-structured magnets consisting of 128 equi-axed, platelet-like\nand columnar-shaped grains show a theoretical maximum energy product of 228\nkJ/m$^3$, 208 kJ/m$^3$, 252 kJ/m$^3$, respectively.\n",
"title": "Micromagnetic Simulations for Coercivity Improvement through Nano-Structuring of Rare-Earth Free L1$_0$-FeNi Magnets"
} | null | null | null | null | true | null | 2984 | null | Default | null | null |
null | {
"abstract": " The joint Value at Risk (VaR) and expected shortfall (ES) quantile regression\nmodel of Taylor (2017) is extended via incorporating a realized measure, to\ndrive the tail risk dynamics, as a potentially more efficient driver than daily\nreturns. Both a maximum likelihood and an adaptive Bayesian Markov Chain Monte\nCarlo method are employed for estimation, whose properties are assessed and\ncompared via a simulation study; results favour the Bayesian approach, which is\nsubsequently employed in a forecasting study of seven market indices and two\nindividual assets. The proposed models are compared to a range of parametric,\nnon-parametric and semi-parametric models, including GARCH, Realized-GARCH and\nthe joint VaR and ES quantile regression models in Taylor (2017). The\ncomparison is in terms of accuracy of one-day-ahead Value-at-Risk and Expected\nShortfall forecasts, over a long forecast sample period that includes the\nglobal financial crisis in 2007-2008. The results favor the proposed models\nincorporating a realized measure, especially when employing the sub-sampled\nRealized Variance and the sub-sampled Realized Range.\n",
"title": "Semi-parametric Dynamic Asymmetric Laplace Models for Tail Risk Forecasting, Incorporating Realized Measures"
} | null | null | null | null | true | null | 2985 | null | Default | null | null |
null | {
"abstract": " The paper addresses the hydrodynamic behavior of a sphere close to a\nmicro-patterned superhydrophobic surface described in terms of alternated\nno-slip and perfect-slip stripes. Physically, the perfect-slip stripes model\nthe parallel grooves where a large gas cushion forms between fluid and solid\nwall, giving rise to slippage at the gas-liquid interface. The potential of the\nboundary element method (BEM) in dealing with mixed no-slip/perfect-slip\nboundary conditions is exploited to systematically calculate the mobility\ntensor for different particle-to-wall relative positions and for different\nparticle radii. The particle hydrodynamics is characterized by a non trivial\nmobility field which presents a distinct near wall behavior where the wall\npatterning directly affects the particle motion. In the far field, the effects\nof the wall pattern can be accurately represented via an effective description\nin terms of a homogeneous wall with a suitably defined apparent slippage. The\ntrajectory of the sphere under the action of an external force is also\ndescribed in some detail. A resonant regime is found when the frequency of the\ntransversal component of the force matches a characteristic crossing frequency\nimposed by the wall pattern. It is found that, under resonance, the particle\nundergoes a mean transversal drift. Since the resonance condition depends on\nthe particle radius the effect can in principle be used to conceive devices for\nparticle sorting based on superhydrophobic surfaces.\n",
"title": "Mobility tensor of a sphere moving on a super-hydrophobic wall: application to particle separation"
} | null | null | null | null | true | null | 2986 | null | Default | null | null |
null | {
"abstract": " In many real-world binary classification tasks (e.g. detection of certain\nobjects from images), an available dataset is imbalanced, i.e., it has much\nless representatives of a one class (a minor class), than of another.\nGenerally, accurate prediction of the minor class is crucial but it's hard to\nachieve since there is not much information about the minor class. One approach\nto deal with this problem is to preliminarily resample the dataset, i.e., add\nnew elements to the dataset or remove existing ones. Resampling can be done in\nvarious ways which raises the problem of choosing the most appropriate one. In\nthis paper we experimentally investigate impact of resampling on classification\naccuracy, compare resampling methods and highlight key points and difficulties\nof resampling.\n",
"title": "Influence of Resampling on Accuracy of Imbalanced Classification"
} | null | null | null | null | true | null | 2987 | null | Default | null | null |
null | {
"abstract": " Researchers have attempted to model information diffusion and topic trends\nand lifecycle on online social networks. They have investigated the role of\ncontent, social connections and communities, familiarity and behavioral\nsimilarity in this context. The current article presents a survey of\nrepresentative models that perform topic analysis, capture information\ndiffusion, and explore the properties of social connections in the context of\nonline social networks. The article concludes with a set of outlines of open\nproblems and possible directions of future research interest. This article is\nintended for researchers to identify the current literature, and explore\npossibilities to improve the art.\n",
"title": "Literature Survey on Interplay of Topics, Information Diffusion and Connections on Social Networks"
} | null | null | [
"Computer Science"
]
| null | true | null | 2988 | null | Validated | null | null |
null | {
"abstract": " The extended form of the classical polynomial cubic B-spline function is used\nto set up a collocation method for some initial boundary value problems derived\nfor the Korteweg-de Vries-Burgers equation. Having nonexistence of third order\nderivatives of the cubic B-splines forces us to reduce the order of the term\nuxxx to give a coupled system of equations. The space discretization of this\nsystem is accomplished by the collocation method following the time\ndiscretization with Crank-Nicolson method. Two initial boundary value problems,\none having analytical solution and the other is set up with a non analytical\ninitial condition, have been simulated by the proposed method.\n",
"title": "Extended B-Spline Collocation Method For KdV-Burgers Equation"
} | null | null | null | null | true | null | 2989 | null | Default | null | null |
null | {
"abstract": " We develop a method to study the implied volatility for exotic options and\nvolatility derivatives with European payoffs such as VIX options. Our approach,\nbased on Malliavin calculus techniques, allows us to describe the properties of\nthe at-the-money implied volatility (ATMI) in terms of the Malliavin\nderivatives of the underlying process. More precisely, we study the short-time\nbehaviour of the ATMI level and skew. As an application, we describe the\nshort-term behavior of the ATMI of VIX and realized variance options in terms\nof the Hurst parameter of the model, and most importantly we describe the class\nof volatility processes that generate a positive skew for the VIX implied\nvolatility. In addition, we find that our ATMI asymptotic formulae perform very\nwell even for large maturities. Several numerical examples are provided to\nsupport our theoretical results.\n",
"title": "On smile properties of volatility derivatives and exotic products: understanding the VIX skew"
} | null | null | null | null | true | null | 2990 | null | Default | null | null |
null | {
"abstract": " We consider the problem of designing risk-sensitive optimal control policies\nfor scheduling packet transmissions in a stochastic wireless network. A single\nclient is connected to an access point (AP) through a wireless channel. Packet\ntransmission incurs a cost $C$, while packet delivery yields a reward of $R$\nunits. The client maintains a finite buffer of size $B$, and a penalty of $L$\nunits is imposed upon packet loss which occurs due to finite queueing buffer.\nWe show that the risk-sensitive optimal control policy for such a simple\nset-up is of threshold type, i.e., it is optimal to carry out packet\ntransmissions only when $Q(t)$, i.e., the queue length at time $t$ exceeds a\ncertain threshold $\\tau$. It is also shown that the value of threshold $\\tau$\nincreases upon increasing the cost per unit packet transmission $C$.\nFurthermore, it is also shown that a threshold policy with threshold equal to\n$\\tau$ is optimal for a set of problems in which cost $C$ lies within an\ninterval $[C_l,C_u]$. Equations that need to be solved in order to obtain\n$C_l,C_u$ are also provided.\n",
"title": "Risk-Sensitive Optimal Control of Queues"
} | null | null | null | null | true | null | 2991 | null | Default | null | null |
null | {
"abstract": " One of the most significant goals of modern science is establishing whether\nlife exists around other suns. The most direct path towards its achievement is\nthe detection and atmospheric characterization of terrestrial exoplanets with\npotentially habitable surface conditions. The nearest ultracool dwarfs (UCDs),\ni.e. very-low-mass stars and brown dwarfs with effective temperatures lower\nthan 2700 K, represent a unique opportunity to reach this goal within the next\ndecade. The potential of the transit method for detecting potentially habitable\nEarth-sized planets around these objects is drastically increased compared to\nEarth-Sun analogs. Furthermore, only a terrestrial planet transiting a nearby\nUCD would be amenable for a thorough atmospheric characterization, including\nthe search for possible biosignatures, with near-future facilities such as the\nJames Webb Space Telescope. In this chapter, we first describe the physical\nproperties of UCDs as well as the unique potential they offer for the detection\nof potentially habitable Earth-sized planets suitable for atmospheric\ncharacterization. Then, we present the SPECULOOS ground-based transit survey,\nthat will search for Earth-sized planets transiting the nearest UCDs, as well\nas its prototype survey on the TRAPPIST telescopes. We conclude by discussing\nthe prospects offered by the recent detection by this prototype survey of a\nsystem of seven temperate Earth-sized planets transiting a nearby UCD,\nTRAPPIST-1.\n",
"title": "SPECULOOS exoplanet search and its prototype on TRAPPIST"
} | null | null | [
"Physics"
]
| null | true | null | 2992 | null | Validated | null | null |
null | {
"abstract": " For $G$ an algebraic group of type $A_l$ over an algebraically closed field\nof characteristic $p$, we determine all irreducible rational representations of\n$G$ in defining characteristic with dimensions $\\le (l+1)^s$ for $s = 3, 4$,\nprovided that $l > 18$, $l > 35$ respectively. We also give explicit\ndescriptions of the corresponding modules for $s = 3$.\n",
"title": "Small-dimensional representations of algebraic groups of type $A_l$"
} | null | null | null | null | true | null | 2993 | null | Default | null | null |
null | {
"abstract": " We report the detection of the prebiotic molecule CH3NCO in a solar-type\nprotostar, IRAS16293-2422 B. A significant abundance of this species on the\nsurface of the comet 67P/Churyumov-Gerasimenko has been proposed, and it has\nrecently been detected in hot cores around high-mass protostars. We observed\nIRAS16293-2422 B with ALMA in the 90 GHz to 265 GHz range, and detected 8\nunblended transitions of CH3NCO. From our Local Thermodynamic Equilibrium\nanalysis we derived an excitation temperature of 110+-19 K and a column density\nof (4.0+-0.3)x10^15 cm^-2 , which results in an abundance of\n<=(1.4+-0.1)x10^-10 with respect to molecular hydrogen. This implies a\nCH3NCO/HNCO and CH3NCO/NH2CHO column density ratios of ~0.08. Our modelling of\nthe chemistry of CH3NCO suggests that both ice surface and gas phase formation\nreactions of this molecule are needed to explain the observations.\n",
"title": "Detection of methylisocyanate (CH3NCO) in a solar-type protostar"
} | null | null | null | null | true | null | 2994 | null | Default | null | null |
null | {
"abstract": " A qualgebra $G$ is a set having two binary operations that satisfy\ncompatibility conditions which are modeled upon a group under conjugation and\nmultiplication. We develop a homology theory for qualgebras and describe a\nclassifying space for it. This space is constructed from $G$-colored prisms\n(products of simplices) and simultaneously generalizes (and includes)\nsimplicial classifying spaces for groups and cubical classifying spaces for\nquandles. Degenerate cells of several types are added to the regular prismatic\ncells; by duality, these correspond to \"non-rigid\" Reidemeister moves and their\nhigher dimensional analogues. Coupled with $G$-coloring techniques, our\nhomology theory yields invariants of knotted trivalent graphs in $\\mathbb{R}^3$\nand knotted foams in $\\mathbb{R}^4$. We re-interpret these invariants as\nhomotopy classes of maps from $S^2$ or $S^3$ to the classifying space of $G$.\n",
"title": "A prismatic classifying space"
} | null | null | null | null | true | null | 2995 | null | Default | null | null |
null | {
"abstract": " Dimension reduction and visualization is a staple of data analytics. Methods\nsuch as Principal Component Analysis (PCA) and Multidimensional Scaling (MDS)\nprovide low dimensional (LD) projections of high dimensional (HD) data while\npreserving an HD relationship between observations. Traditional biplots assign\nmeaning to the LD space of a PCA projection by displaying LD axes for the\nattributes. These axes, however, are specific to the linear projection used in\nPCA. MDS projections, which allow for arbitrary stress and dissimilarity\nfunctions, require special care when labeling the LD space. We propose an\niterative scheme to plot an LD axis for each attribute based on the\nuser-specified stress and dissimilarity metrics. We discuss the details of our\ngeneral biplot methodology, its relationship with PCA-derived biplots, and\nprovide examples using real data.\n",
"title": "Generalized Biplots for Multidimensional Scaled Projections"
} | null | null | null | null | true | null | 2996 | null | Default | null | null |
null | {
"abstract": " We introduce a new model for building conditional generative models in a\nsemi-supervised setting to conditionally generate data given attributes by\nadapting the GAN framework. The proposed semi-supervised GAN (SS-GAN) model\nuses a pair of stacked discriminators to learn the marginal distribution of the\ndata, and the conditional distribution of the attributes given the data\nrespectively. In the semi-supervised setting, the marginal distribution (which\nis often harder to learn) is learned from the labeled + unlabeled data, and the\nconditional distribution is learned purely from the labeled data. Our\nexperimental results demonstrate that this model performs significantly better\ncompared to existing semi-supervised conditional GAN models.\n",
"title": "Semi-supervised Conditional GANs"
} | null | null | null | null | true | null | 2997 | null | Default | null | null |
null | {
"abstract": " In this work, we build on recent advances in distributional reinforcement\nlearning to give a generally applicable, flexible, and state-of-the-art\ndistributional variant of DQN. We achieve this by using quantile regression to\napproximate the full quantile function for the state-action return\ndistribution. By reparameterizing a distribution over the sample space, this\nyields an implicitly defined return distribution and gives rise to a large\nclass of risk-sensitive policies. We demonstrate improved performance on the 57\nAtari 2600 games in the ALE, and use our algorithm's implicitly defined\ndistributions to study the effects of risk-sensitive policies in Atari games.\n",
"title": "Implicit Quantile Networks for Distributional Reinforcement Learning"
} | null | null | [
"Statistics"
]
| null | true | null | 2998 | null | Validated | null | null |
null | {
"abstract": " The bacterial genome is organized in a structure called the nucleoid by a\nvariety of associated proteins. These proteins can form complexes on DNA that\nplay a central role in various biological processes, including chromosome\nsegregation. A prominent example is the large ParB-DNA complex, which forms an\nessential component of the segregation machinery in many bacteria. ChIP-Seq\nexperiments show that ParB proteins localize around centromere-like parS sites\non the DNA to which ParB binds specifically, and spreads from there over large\nsections of the chromosome. Recent theoretical and experimental studies suggest\nthat DNA-bound ParB proteins can interact with each other to condense into a\ncoherent 3D complex on the DNA. However, the structural organization of this\nprotein-DNA complex remains unclear, and a predictive quantitative theory for\nthe distribution of ParB proteins on DNA is lacking. Here, we propose the\nLooping and Clustering (LC) model, which employs a statistical physics approach\nto describe protein-DNA complexes. The LC model accounts for the extrusion of\nDNA loops from a cluster of interacting DNA-bound proteins. Conceptually, the\nstructure of the protein-DNA complex is determined by a competition between\nattractive protein interactions and the configurational and loop entropy of\nthis protein-DNA cluster. Indeed, we show that the protein interaction strength\ndetermines the \"tightness\" of the loopy protein-DNA complex. With this approach\nwe consider the genomic organization of such a protein-DNA cluster around a\nsingle high-affinity binding site. Thus, our model provides a theoretical\nframework to quantitatively compute the binding profiles of ParB-like proteins\naround a cognate (parS) binding site.\n",
"title": "Looping and Clustering model for the organization of protein-DNA complexes on the bacterial genome"
} | null | null | null | null | true | null | 2999 | null | Default | null | null |
null | {
"abstract": " For a single equation in a system of linear equations, estimation by\ninstrumental variables is the standard approach. In practice, however, it is\noften difficult to find valid instruments. This paper proposes a maximum\nlikelihood method that does not require instrumental variables; it is\nillustrated by simulation and with a real data set.\n",
"title": "Simultaneous-equation Estimation without Instrumental Variables"
} | null | null | [
"Mathematics",
"Statistics"
]
| null | true | null | 3000 | null | Validated | null | null |
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