Testing cosmological isotropy with gravitational waves and gamma-ray bursts

TL;DR

This study tests the cosmological principle's assumption of isotropy using recent gravitational wave and gamma-ray burst data, employing multiple statistical methods, and finds no significant evidence of anisotropy.

Contribution

It extends previous analyses by incorporating the latest datasets and multiple statistical tests to assess cosmological isotropy.

Findings

No significant anisotropy detected in GW and GRB data.

Results are consistent with the cosmological principle.

Uses multiple statistical methods for robust analysis.

Abstract

The cosmological principle asserts that the Universe is homogeneous and isotropic on large enough scales. However, alternative cosmological models can bring about anisotropies through local inhomogeneities, anisotropic evolution, or exotic physics. In addition, select studies have also hinted at mild evidence of anisotropies in SNe Ia, CMB, and GRB data, though these remain unconfirmed. In this work, we test for cosmological anisotropies using gravitational waves and gamma-ray bursts, adopting the latest O4a release from the LIGO-Virgo-KAGRA collaboration and GRBWeb (including all known GRBs since 1991). If the cosmological principle holds, the sky localisation and the characteristics of the GRBs and GWs (masses, luminosities, redshifts) should be statistically isotropic when corrected for selection biases. We employ a couple statistical methods, including angular power spectra and two-point correlation functions, and compare the results against synthetic data. The work extends previous analyses by including the most recent datasets, and the use of multiple complementary statistical tests. We find no significant evidence for anisotropy in the current GW and GRB datasets, consistent with the cosmological principle.