# Cosmic Anisotropy and Fast Radio Bursts

## TL;DR

This study uses simulations of fast radio bursts to determine the number of observations needed to detect or rule out cosmic anisotropy, focusing on dipole structures with varying amplitudes.

## Contribution

It provides the first estimates of the sample size of FRBs required to detect cosmic dipoles of different amplitudes through simulations.

## Key findings

- At least 2800 FRBs are needed to detect a dipole with amplitude 0.01.
- Approximately 190 FRBs are sufficient for a dipole with amplitude 0.03.
- Only 20 FRBs could detect a large dipole with amplitude 0.1.

## Abstract

In the recent years, the field of fast radio bursts (FRBs) is thriving and growing rapidly. It is of interest to study cosmology by using FRBs with known redshifts. In the present work, we try to test the possible cosmic anisotropy with the simulated FRBs. In particular, we only consider the possible dipole in FRBs, rather than the cosmic anisotropy in general, while the analysis is only concerned with finding the rough number of necessary data points to distinguish a dipole from a monopole structure through simulations. Noting that there is no a large sample of actual data of FRBs with known redshifts by now, simulations are necessary to this end. We find that at least 2800, 190, 100 FRBs are competent to find the cosmic dipole with amplitude 0.01, 0.03, 0.05, respectively. Unfortunately, even 10000 FRBs are not competent to find the tiny cosmic dipole with amplitude of ${\cal O}(10^{-3})$. On the other hand, at least 20 FRBs with known redshifts are competent to find the cosmic dipole with amplitude 0.1. We expect that such a big cosmic dipole could be ruled out by using only a few tens of FRBs with known redshifts in the near future.