theory. The reason for this is, among other things, that quantum field theories of gravity generally break down before reaching the Planck scale. As a consequence, we have no reliable theory for the very early universe. Some physicists consider it to be ad hoc and inelegant, requiring 19 numerical constants whose values are unrelated and arbitrary. Although the Standard Model, as it now stands, can explain why neutrinos have masses, the specifics of neutrino mass are still unclear. It is believed that explaining neutrino mass will require an additional 7 or 8 constants, which are also arbitrary parameters. The Higgs mechanism gives rise to the hierarchy problem if some new physics (coupled to the Higgs) is present at high energy scales. In these cases, in order for the weak scale to be much smaller than the Planck scale, severe fine tuning of the parameters is required; there are, however, other scenarios that include quantum gravity in which such fine tuning can be avoided. There are also issues of quantum triviality, which suggests that it may not be possible to create a consistent quantum field theory involving elementary scalar particles. The model is inconsistent with the emerging Lambda-CDM model of cosmology. Contentions include the absence of an explanation in the Standard Model of particle physics for the observed amount of cold dark matter (CDM) and its contributions to dark energy, which are many orders of magnitude too large. It is also difficult to accommodate the observed predominance of matter over antimatter (matter/antimatter asymmetry). The isotropy and homogeneity of the visible universe over large distances seems to require a mechanism like cosmic inflation, which would also constitute an extension of the Standard Model. Currently, no proposed theory of everything has been widely accepted or verified. See also Yang–Mills theory Fundamental interaction: Quantum electrodynamics Strong interaction: Color charge, Quantum chromodynamics, Quark model Weak interaction: Electroweak interaction, Fermi's interaction, Weak hypercharge, Weak isospin Gauge theory: Introduction to gauge theory Generation Higgs mechanism: Higgs boson, Alternatives to the Standard Higgs Model Lagrangian Open questions: CP violation, Neutrino masses, QCD matter, Quantum triviality Quantum field theory Standard Model: Mathematical formulation of, Physics beyond the Standard Model Electron electric dipole moment Notes References Further reading Introductory textbooks Advanced textbooks Highlights the gauge theory aspects of the Standard Model. Highlights dynamical and phenomenological aspects of the Standard Model. 920 pages. 952 pages. 670 pages. Highlights group-theoretical aspects of