# Exploring New Physics Beyond the Standard Cosmology with Dark Energy Survey Year 1 Data

## TL;DR

This study uses DES Year 1 data combined with other observations to test three alternative dark energy models, finding no evidence for new physics but alleviating the $\sigma_8$ tension.

## Contribution

It provides updated constraints on interacting, viscous, and dynamical dark energy models using combined cosmological datasets, exploring their potential to resolve the $\sigma_8$ tension.

## Key findings

- No evidence for dark matter-dark energy interaction.
- Stringent limit on dark energy viscosity coefficient.
- No indication of dynamical dark energy.

## Abstract

With the recent data from the first year of the Dark Energy Survey (DES Y1), we attempt to probe whether there is new physics beyond the standard cosmology and to reconcile the $\sigma_8$ tension between the DES Y1 and Planck datasets in three alternative cosmological models. Combining the galaxy clustering and weak gravitational lensing data from the DES Y1 with other cosmological observations including cosmic microwave background radiation, baryon acoustic oscillations, Type Ia supernovae (SNe Ia) and Planck lensing, we find that: (i) For the interacting dark energy model, we have an updated constraint on the modified matter expansion rate $\epsilon=-0.00004\pm 0.00031$, which indicates that there is no hint of interaction between dark matter and dark energy in the dark sector of the universe; (ii) For the viscous dark energy model, up to now, the strictest constraint on the bulk viscosity coefficient $\eta<0.00152$ at the $2\sigma$ confidence level is obtained; (iii) For the dynamical dark energy model, our constraint on the typical parameter $\beta=-0.04\pm0.12$ implies that there is still no evidence of dynamical dark energy. Meanwhile, we find the $\sigma_8$ tension can be effectively alleviated in the above three alternatives by constraining them with the DES Y1 and Planck datasets separately.