Signals on the power spectra of a cosmology modeled with Chebyshev polynomials

TL;DR

This paper models interactions between dark matter and dark energy using Chebyshev polynomials, analyzing their effects on cosmic structure growth and power spectra, and constrains these models with observational data.

Contribution

It introduces a novel phenomenological interaction model with Chebyshev polynomial parametrization for dark sector interactions and constrains it using MCMC analysis.

Findings

Structure growth deviates from the standard model.

Matter power spectrum is sensitive to the interaction term.

CMB temperature spectrum amplitude varies with interaction parameters.

Abstract

We present an interacting model with a phenomenological interaction, $\bar{Q}$, between a cold dark matter (DM) fluid and a dark energy (DE) fluid, which takes a time-varying equation of state (EoS) parameter, $\mathrm{\omega_{DE}}$. Here, both $\bar{Q}$ and $\mathrm{\omega_{DE}}$ are modeled in terms of the Chebyschev polynomials. In a Newtonian gauge and on sub-horizon scales, a set of perturbed equations is obtained when the momentum transfer potential becomes null in the DM rest-frame. This leads to different cases of the interacting model. Then, via a Markov-Chain Monte Carlo (MCMC) method, we constrain such cases by using a combined analysis of geometric and dynamical data. Our results show that in such cases the evolution curves of the structure growth of the matter deviate strongly from the standard model. In addition, we also found that the matter power spectrum is sensitive to $\bar{Q}$. In this way, the coupling modifies the matter scale and generates a slight variation of the turnover point to smaller scales. Likewise, the amplitude of the CMB temperature power spectrum is sensitive the values of $\bar{Q}$ and $\mathrm{\omega_{DE}}$ at low and high multipoles $\it l$, respectively. Here, $\bar{Q}$ can cross twice the line $\bar{Q}=0$ during its background evolution.