Illuminating the dark universe in the multi-messenger era

TL;DR

This review discusses how multi-messenger astronomy and various astrophysical observations are used to explore and constrain the nature of dark matter, dark energy, and modifications to gravity, highlighting recent advances and future prospects.

Contribution

It provides a comprehensive overview of observational constraints on dark matter and modified gravity models across multiple scales and phenomena, integrating recent data and future experimental prospects.

Findings

Current observations place strong limits on dark matter properties.

Gravitational wave data constrains alternative gravity theories.

Upcoming experiments will further test dark sector models.

Abstract

The precision era of multi-messenger astronomy, together with modern astrophysical, cosmological, and gravitational wave observations, increasingly points toward the existence of a ``dark" sector that cannot be explained within the framework of the Standard Model of particle physics and General Relativity. In this review, we explore extensions of standard physics and examine how observational data can be used to probe new particles and interactions. We consider a wide range of scales, from Solar System tests to galactic and cosmological observations, and investigate both conventional dark matter candidates, such as weakly interacting massive particles, and alternative scenarios including ultralight fields and primordial black holes. We discuss constraints derived from compact objects such as neutron stars, black holes, pulsars, and magnetars observations as well as from high-energy astrophysical phenomena. In addition, we analyze extensions of General Relativity involving additional scalar fields and their impact on gravitational wave signals and stochastic backgrounds from primordial black holes. We also study the capture and accumulation of dark matter in compact objects, which can alter properties such as mass, radius, and tidal deformability, and consider scenarios in which dark matter decays into Standard Model particles. While current observations already place significant limits on dark matter and modified-gravity models, upcoming experiments and observatories are expected to further probe or discover such new physics by improving constraints on particle masses and interaction strengths.