Structure formation in a Dirac-Milne universe: comparison with the standard cosmological model

TL;DR

This study compares structure formation in the standard $ m f ext{Lambda CDM}$ cosmology and the Dirac-Milne universe, revealing differences in formation speed and redshift endpoints, with implications for observed matter power spectra.

Contribution

It provides the first numerical comparison of structure formation in the Dirac-Milne universe with the standard cosmological model, highlighting key differences and potential observational signatures.

Findings

Structure formation is faster in the Dirac-Milne universe.

Both models predict structure formation ends near redshift 3 and 0.5 respectively.

Matter-antimatter domains of small initial size could explain observed matter power spectrum.

Abstract

The presence of complex hierarchical gravitational structures is one of the main features of the observed universe. Here, structure formation is studied both for the standard ($\Lambda \rm CDM$) cosmological model and for the Dirac-Milne universe, a matter-antimatter symmetric universe that was {\gm recently} proposed as an alternative "coasting" cosmological scenario. One-dimensional numerical simulations reveal the analogies and differences between the two models. Although structure formation is faster in the Dirac-Milne universe, both models predict that it ends shortly before the present epoch, at cosmological redshift $z \approx 3$ for the Dirac-Milne cosmology, and at $z \approx 0.5$ for the $\Lambda \rm CDM$ universe. The present results suggest that the matter power spectrum observed by the Sloan Digital Sky Survey might be entirely due to the nonlinear evolution of matter and antimatter domains of relatively small initial dimensions, of the order of a few tens of parsecs comoving at cosmological redshift $z =1080$.