The integrated Sachs-Wolfe effect in cosmologies with coupled dark matter and dark energy

TL;DR

This paper derives the integrated Sachs-Wolfe effect in cosmologies with coupled dark matter and dark energy, highlighting how such couplings alter the effect's characteristics and potential observational signatures.

Contribution

It provides a theoretical derivation of the iSW effect in coupled dark sector models and explores how decay rates and equations of state influence the signal.

Findings

iSW spectra are affected by dark matter decay and dark energy properties

Coupled models can be distinguished through precise iSW measurements

Analogies with gravitational lensing are discussed

Abstract

The subject of this paper is the derivation of the integrated Sachs-Wolfe (iSW) effect in cosmologies with coupled dark matter and dark energy fluids. These couplings influence the iSW-effect in three ways: The Hubble function assumes a different scaling, the structure growth rate shows a different time evolution, and in addition, the Poisson equation, which relates the density perturbations to fluctuations in the gravitational potential, is changed, due to the violation of the scaling rho ~ a^{-3} of the matter density rho with scale factor a. Exemplarily, I derive the iSW-spectra for a model in which dark matter decays into dark energy, investigate the influence of the dark matter decay rate and the dark energy equation of state on the iSW-signal, and discuss the analogies for gravitational lensing. Quite generally iSW-measurements should reach similar accuracy in determining the dark energy equation of state parameter and the coupling constant.