# Gravitino/Axino as Decaying Dark Matter and Cosmological Tensions

## TL;DR

This paper explores supersymmetric axion models where gravitino or axino serve as decaying dark matter, potentially addressing cosmological tensions by extending the standard ΛCDM model.

## Contribution

It demonstrates that in these models, the next-to-lightest supersymmetric particle naturally has a lifetime comparable to the universe's age, providing a viable decaying dark matter scenario.

## Key findings

- NLSP lifetime is comparable to the universe's age in certain parameter regions
- Decaying dark matter can help alleviate cosmological tensions
- Supersymmetric axion models offer a well-motivated framework for such scenarios

## Abstract

In supersymmetric axion models, if the gravitino or axino is the lightest SUSY particle (LSP), the other is often the next-to-LSP (NLSP). We investigate the cosmology of such a scenario and point out that the lifetime of the NLSP naturally becomes comparable to the present age of the universe in a viable parameter region. This is a well-motivated example of the so-called decaying dark matter model, which is recently considered as an extension of the $\Lambda$CDM model to relax some cosmological tensions.