Dark matter from Modified Friedmann Dynamics

TL;DR

This paper explores Modified Friedmann Dynamics (MOFD) as a relativistic framework to explain dark matter and cosmic acceleration, comparing it with MOND and observational data, and analyzing its viability against standard models.

Contribution

It introduces a relativistic MOFD model based on generalized Raychaudhuri equations, linking it to MOND and assessing its compatibility with cosmological observations.

Findings

MOFD can explain some dark matter effects in the accelerating universe.

MOND cosmologies are compatible with acceleration only at high cosmological constant values.

Statistical analysis shows limited evidence favoring MOFD over ΛCDM, with parameter values inconsistent with galaxy rotation curves.

Abstract

The contemporary cosmic expansion is considered in the context of Modified Friedmann Dynamics (MOFD). We discuss some relativistic model exploring analogy to MOND modification of Newtonian dynamics. We argue that MOFD cosmologies can explain fraction of dark matter in the accelerating Universe. We discuss some observational constraints on possible evolutional MOFD scenarios of cosmological models coming from SN Ia distant supernovae. We show that Modified Newtonian Dynamics can be obtained as a Newtonian limit of more general relativistic models with polytropic component of Equation of State. They constitute a special subclass of generalized Cardassian models basing on generalization of the Raychaudhuri equation rather than on generalization of the Friedmann first integral. We demonstrate that MOND cosmologies are compatible with observed accelerated phase of expansion of current universe only for high value of cosmological constant. The Bayesian framework of model selection favored this model over $\Lambda$CDM model if $\Omega_{m,o}$ is fixed but this evidence is not significant. Moreover obtained from statistical analysis value of the MOND characteristic $\beta$ parameter is far from value required for explanation of the flat rotation curves of spiral galaxies.