On the initial conditions of the $\nu$HDM cosmological model

TL;DR

This paper investigates initial conditions for the $ u$HDM cosmological model based on Milgromian Dynamics, using Bayesian analysis of CMB data to inform structure formation simulations, revealing distinct evolution scenarios and parameter estimates.

Contribution

It provides the first Bayesian analysis of $ u$HDM initial conditions derived from CMB data, highlighting differences from standard cosmology and setting the stage for further simulations.

Findings

H0 approximately 56 km/s/Mpc, lower than standard models

Omega_m0 around 0.5, indicating different matter density evolution

Distinct power spectrum evolution scenario suggested by excess power

Abstract

The $\nu$HDM is the only cosmological model based on Milgromian Dynamics (MOND) with available structure formation simulations. While MOND accounts for galaxies, with a priori predictions for spirals and ellipticals, a light sterile neutrino of 11 eV can assist in recovering scaling relations on the galaxy-cluster scales. In order to perform MONDian cosmological simulations in this theoretical approach, initial conditions derived from a fit to the angular power spectrum of Cosmic Microwave Background (CMB) fluctuations are required. In this work, we employ CosmoSIS to perform a Bayesian study of the $\nu$HDM model. Using the best-fit values of the posterior, the CMB power spectrum is reevaluated. The excess of power in the transfer function implies a distinct evolution scenario, which can be used further as an input for a set of hydro-dynamical calculations. The resulting values H0 $\approx$ 56 km/s/Mpc and ${\Omega}_{m_{0}} \approx 0.5$ are far from agreement with respect to the best fit ones in the canonical Cold Dark Matter model, but may be significant in MONDian cosmology. The assumed Planck CMB initial conditions are only valid for the $\Lambda$CDM cosmology. This work constitutes a first step in an iterative procedure needed to disentangle the model dependence of the derived initial density and velocity fields.