Dark Energy and Dark Matter Interaction: Kernels of Volterra Type and Coincidence Problem

TL;DR

This paper introduces an exactly solvable cosmological model with Volterra-type kernels describing Dark Energy and Dark Matter interaction, offering solutions that address the Coincidence problem and various Rip regimes.

Contribution

It presents a novel, exactly solvable model of Dark Sector interaction using Volterra kernels, with explicit solutions and asymptotic analysis.

Findings

Exact solutions classified by discriminant sign

Model can realize Big Rip, Little Rip, Pseudo Rip scenarios

Memory effects can solve the Coincidence problem

Abstract

We study a new exactly solvable model of coupling of the Dark Energy and Dark Matter, in the framework of which the kernel of non-gravitational interaction is presented by the integral Volterra-type operator well-known in the classical theory of fading memory. Exact solutions of this isotropic homogeneous cosmological model were classified with respect to the sign of the discriminant of the cubic characteristic polynomial associated with the key equation of the model. Energy-density scalars of the Dark Energy and Dark Matter, the Hubble function and acceleration parameter are presented explicitly; the scale factor is found in quadratures. Asymptotic analysis of the exact solutions has shown that the Big Rip, Little Rip, Pseudo Rip regimes can be realized with the specific choice of guiding parameters of the model. We show that the Coincidence problem can be solved if we consider the memory effect associated with the interactions in the Dark Sector of the Universe.