Indications of a Late-Time Transition to a Strongly Interacting Dark Sector

TL;DR

This paper investigates a model where dark energy and dark matter interact strongly after a certain redshift, using cosmological data to identify the epoch of this transition and its implications for dark sector physics.

Contribution

It introduces a redshift-dependent interaction model between dark energy and dark matter, constrained by multiple late-time cosmological observations, revealing a late-time transition to strong interaction.

Findings

Indicates a late-time transition redshift below 0.624.

Supports a strong energy transfer from dark energy to dark matter at low redshifts.

Fits observational data similarly to CPL parametrization without crossing the phantom divide.

Abstract

We explore the transition from the $\Lambda$CDM to an interacting dark sector by introducing a model with a redshift threshold that controls the onset of the energy transfer between the dark energy and the dark matter. Below the transition redshift, the interaction between dark matter and dark energy becomes active, while at earlier times the cosmological evolution coincides with that of $\Lambda$CDM. This approach allows us to determine the epoch in the comic history where the interacting effects have an impact in the description of the dark sector. We constrain the free parameters of the model using late-time cosmological observations, namely Cosmic Chronometers, DESI DR2 Baryonic Acoustic Oscillations, and Supernova data from the Pantheon Plus, Union3.0, and DES-Dovekie catalogues. The analysis provides an indication of a strong interacting term that describes energy transfer from dark energy to dark matter, which is activated at low redshifts. The PantheonPlus sample provides a threshold of $z_{T}<0.624$, the Union3.0 sample yields $z_{T}=0.400_{-0.23}^{+0.021}$, and the DES-Dovekie sample gives $z_{T}=0.371_{-0.26}^{+0.028}$. The model fits the data in a similar way to the CPL parametrization, without the dark energy to cross the phantom divide line.