2025/09/14 by Kazem Rezazadeh, Rezazadeh, Kazem, E. Yusofi +3
Physics and Astronomy · Earth and Planetary Sciences · #Cosmology and Gravitation Theories #Geophysics and Gravity Measurements #Relativity and Gravitational Theory
paper · pdf · doi:10.48550/arxiv.2509.11138
We propose that dark matter (DM) possesses a quadratic equation of state, which becomes significant at high densities, altering the Universe's evolution during its early stages. We derive the modified background evolution equations for the Hubble parameter H(z) and the DM density parameter Ωdm(z). We then perturb the governing equations to study the linear growth of matter fluctuations, computing the observable growth factor fσ8(z). Finally, we compare the model with the latest cosmological data, including Hubble parameter H(z) measurements, and growth factor fσ8(z) data, up to z=3. Our results indicate that the quadratic model, while remaining consistent with background observations, offers a distinct imprint on the growth of structure, providing not only a new phenomenological avenue to address cosmological tensions but also shedding light on the nature of DM.