# Selected topics in theory and observations of Dark Energy (ITP Cosmology Tunch) + Journal Club

#### Tuesday, PW 12, Room 056

##### 13:00 - 15:00

Go to the calendar of Wednesday Cosmology seminars (Normally on Wednesday, 5pm, Phil 16)

### Seminar calendar

##### 20th March 2018: Selected topics in theory and observations of Dark Energy (Tunch)

Tunch available ()

##### 6th March 2018: Selected topics in theory and observations of Dark Energy (Tunch)

Tunch available ()

##### 20th February 2018: Selected topics in theory and observations of Dark Energy (Tunch)

Tunch available ()

##### 6th February 2018: Selected topics in theory and observations of Dark Energy (Tunch)

Tunch available ()

##### 23rd January 2018: Selected topics in theory and observations of Dark Energy (Tunch)

Tunch available ()

##### 19th December 2018: Selected topics in theory and observations of Dark Energy (Tunch)

Tunch available ()

##### 28th November 2017: Selected topics in theory and observations of Dark Energy (Tunch)

Tunch available ()

##### 16th November 2017: Selected topics in theory and observations of Dark Energy (Tunch)

Lorenzo Pizzuti- “Modified gravity with galaxy cluster mass profiles: from data to simulations”

Abstract: I will provide a brief overview of my work concerning constraints on modified gravity models obtained using galaxy cluster mass profile determinations. In particular, I will present the results of a paper in which we combined the information given by the kinematics of galaxies in clusters with the information provided by lensing analyses for 2 galaxy clusters of the CLASH-CLASH\VLT collaboration to get constraints on f(R) models. In order to discuss the applicability of the proposed method in view of future imaging and spectroscopic surveys, I will further introduce my current study of cosmological simulations, aiming at estimating and calibrating the impact of systematics.

##### 7th November 2017: Journal Club

An alternative to the LCDM model: the case of scale invariance

arXiv arXiv:1701.03964

##### 26th October 2017, 13:30, Ground Floor of Philosophenweg 16: Journal Club (NOTE UNUSUAL DATE AND TIME)

Special JC on Gravitational Waves detection

Caroline Heneka - Strong constraints on cosmological gravity from GW170817 and GRB 170817A - 1710.06394

Martin Pauly - GW170817 Falsifies Dark Matter Emulators - 1710.06168

Ana Marta Pinho - Welcome to the multi-messenger Era! Lessons from a neutron star and the landscape ahead - 1710.05931

Alessio Spurio Mancini - Dark Energy after GW170817 - 1710.05901

##### 11th July : Selected topics in theory and observations of Dark Energy (Tunch)

Martin Pauly (ITP, Heidelberg) - “Predictions of renormalized Higgs inflation”

Abstract: Higgs inflation is a model, that allows to explain inflation with the standard model degrees of freedom by introducing an additional coupling between the Higgs field and gravity. In this talk, I am going to explore the influence of the running of the standard model couplings on the observational predictions of Higgs inflation. In particular, the running of the Higgs-self-coupling and sudden changes in that coupling will be important. These sudden changes can be induced by the effective-field-theory nature of Higgs inflation. I will show that as long as the coupling stays sufficiently large in the inflationary region the predictions are insensitive to the running and become sensitive once the coupling approaches the critical point.

##### 4th July : Journal Club

Caroline Heneka
Safely smoothing spacetime: backreaction in relativistic cosmological simulations
arXiv:1706.09309

Javier Rubio
Primordial Black Hole production in Critical Higgs Inflation
arXiv:1705.04861

##### 27th June : Selected topics in theory and observations of Dark Energy (Tunch)

Cornelius Rampf (ITP, Heidelberg University ) - “Shell-crossing in quasi one-dimensional flow ”

Abstract: So far exact analytic solutions to the cosmological fluid equations existed for initial data that only depend on one space variable. Exact solutions (until shell-crossing) play an important role in cosmology, not only because they are simple but because the breakdown of smooth 3D solution through the development of infinite density caustics begins generically as an almost 1D phenomenon with the formation of pancakes. I present recent work on quasi-one-dimensional (Q1D) flow that depends on all three coordinates but differs only slightly from a strictly 1D flow, thereby allowing a perturbative treatment of shell-crossing using the Euler-Poisson equations written in Lagrangian coordinates. The signature of shell-crossing is then just the vanishing of the Jacobian of the Lagrangian map, a regular perturbation problem. In essence, the problem of the first shell-crossing, which is highly singular in Eulerian coordinates, has been desingularized by switching to Lagrangian coordinates, and can then be handled by perturbation theory. All-order recursion relations are obtained for the time-Taylor coefficients of the displacement field, and it is shown that the Taylor series has an infinite radius of convergence. This allows the determination of the time and location of the first shell-crossing, which is generically shown to be taking place earlier than for the unperturbed 1D flow.

##### 20th June : Journal Club

Caroline Heneka
Improving constraints on the growth rate of structure by modelling the density-velocity cross-correlation in the 6dF Galaxy Survey
arXiv:1706.05205

##### 13th June : Selected topics in theory and observations of Dark Energy (Tunch)

Santiago Casas (ITP, Heidelberg University) - “Non-linear structure formation”

##### 30th May : Selected topics in theory and observations of Dark Energy (Tunch)

Javier Rubio (ITP, Heidelberg University) - “Scale invariance: connecting inflation and dark energy”

Abstract: Inflation and dark energy share many essential properties. I will show that these two eras can be accommodated into a common framework based on scale invariance. I will discuss the phenomenological consequences of two scenarios based on i) exact scale symmetry and ii) broken scale invariance with symmetry resurgence at UV and IR fixed points.

##### 23rd May : Journal Club

Henrik Nersisyan
A Nonlocal Approach to the Cosmological Constant Problem
arXiv:1703.09715

Martin Pauly
Primordial black hole constraints for extended mass functions
arXiv:1705.05567

##### 16th May : Selected topics in theory and observations of Dark Energy (Tunch)

Alefe Almeida(ITP, Heidelberg University) - ” A method for evaluating models that use galaxy rotation curves to derive matter density profiles”

Abstract: There are some approaches, either based on GR or modified gravity that use galaxy rotation to derive the matter density of the corresponding galaxy. In this work, we proposed a test for evaluating them.

##### 9th May Journal Club

Kevin Wolz

Ana Marta Pinho
Stability of fundamental couplings: a global analysis
arXiv:1701.08724

##### 25th April : Selected topics in theory and observations of Dark Energy (Tunch)

Yves Dirian (Geneva University ) - “A numerical relativity scheme for cosmological simulations”

Abstract: I present a new 3+1 integration scheme which allows one to pass an adaptation of the robustness test to the cosmological context, at least in the case of General Relativity with a pressureless perfect fluid field. As an interesting by-product of this construction, a novel constraint-damping method is obtained.

##### 18th April : Journal Club

Viviana Niro

Dario Bettoni
Gravitational Waves in Doubly Coupled Bigravity
arXiv:1703.08016
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