High-redshift Cosmology by Gamma-Ray Bursts: an overview

TL;DR

This paper reviews how Gamma-Ray Bursts can be used as cosmological tools, discussing correlations, theoretical models, and methods to improve their application in understanding the universe's evolution and addressing cosmological tensions.

Contribution

It provides a comprehensive overview of GRB correlations, their theoretical basis, and their potential in cosmology, including new methods like machine learning and cosmography.

Findings

GRBs extend observations up to redshift ~9.

Correcting for biases improves intrinsic relations.

Combining multiple probes enhances cosmological constraints.

Abstract

Several correlations among Gamma-Ray Bursts (GRBs) quantities, both in the prompt and afterglow emissions, have been established during the last decades, thus enabling the standardization of GRBs as cosmological probes. Since GRBs are observed up to redshift $z \sim 9$, they represent a valuable tool to fill in the gap of information on the Universe evolution between the farthest type Ia supernovae and the Cosmic Microwave Background Radiation and to shed new light on the current challenging cosmological tensions. Without claiming for completeness, here we describe the state of the art of GRB correlations, their theoretical interpretations, and their cosmological applications both as standalone probes and in combination with other probes. In this framework, we pinpoint the importance of correcting the correlations for selection biases and redshift evolution to derive intrinsic relations, the assets of combining probes at different scales, and the need for the employment of the appropriate cosmological likelihood to precisely constrain cosmological parameters. Furthermore, we emphasize the benefits of the cosmographic approach to avoid any cosmological assumptions and the valuable applications of machine learning techniques to reconstruct GRB light curves and predict unknown GRB redshifts. Finally, we stress the relevance of all these factors, along with future observations, to definitely boost the power of GRBs in cosmology.