Probing Matter Scaling Beyond ΛCDM with Roman Simulations

The ΛCDM model has had remarkable success in explaining largescale

cosmological observations. But the phenomenological nature of our

assumptions about the dark sector motivates us to investigate any possible

discrepancies with them. For instance, the standard ΛCDM model

assumes that the matter density scales as the inverse cubic power of the

scale factor, that is, ρ_m(a) ∼ a⁻³ or equivalently ρ_m(z) ∼ (1 + z)³.

We will investigate a potential deviation from cubic behavior, such as

ρ_m(z) ∼ (1 + z)^3+ε. The parameter ε will encode the said deviation.

These deviations are enhanced and noticeable at higher redshifts, making

the Roman Space Telescope (z ∼ 2) the ideal probe to help us investigate

them. Using SNANA, we simulate Roman-like SN Ia observations, treating

ΛCDM (ε = 0) as our baseline model, and testing a few alternative

scenarios (ε ≠ 0). Through these simulations, we will obtain a better constraint

on ε, and any departure from the cubic nature of matter scaling

will hint at a beyond ΛCDM universe.