Abstract

Observations of the universe on very small and large scales have revealed a surprising economy in its basic laws and structure. In this light, we have attempted to find new, far more minimal solution to cosmology’s central puzzles. Instead of postulating a pre-hot big bang period such as inflation, we extrapolate the observed universe all the way back to the singularity. Instead of adding new particles and forces, we assume only the Standard Model (including right handed neutrinos) and improve it to maintain local scale symmetry. With this improvement, the hot plasma does not “see” space shrink away at the bang, which becomes a kind of mirror. The simplest-yet proposed dark matter candidate—a stable, right handed neutrino—is then viable. We calculate the gravitational entropy for realistic cosmologies, with radiation, matter, lambda and space curvature and find it favours flat, homogeneous and isotropic universes like ours, with a small positive cosmological constant. Recently, we have also computed the primordial fluctuations in terms of Standard Model couplings. Subject to a couple of key assumptions, the amplitude and spectral tilt agree with the observed values, with no free parameters. (See arXiv:2302.00344 and references therein). In principle, all features of the LCDM model are thereby explained without requiring inflation or any new particles. I’ll also briefly discuss future observational tests.