Search for Stochastic Gravitational-Wave Background from Massive Gravity in the NANOGrav 12.5-Year Data Set

TL;DR

This paper investigates the potential for a stochastic gravitational-wave background from massive gravity using NANOGrav data, finding no significant evidence for graviton mass effects and setting upper limits on the amplitude for small graviton masses.

Contribution

It introduces an analysis of NANOGrav data to test for massive gravity effects, providing new upper limits on graviton mass and the SGWB amplitude.

Findings

Massless graviton is preferred based on Bayes factor.

No significant evidence of dispersion-related correlations.

Upper limit on SGWB amplitude for graviton mass < 10^{-23} eV.

Abstract

Gravitational waves offer a new window to probe the nature of gravity, including answering if the mediating particle, graviton, has a non-zero mass or not. Pulsar timing arrays measure stochastic gravitational wave background (SGWB) at $\sim1-100$~nanohertz. Recently, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration reported an uncorrelated common-spectrum process in their 12.5-year data set with no substantial evidence that the process comes from the SGWB predicted by general relativity. In this work, we explore the possibility of an SGWB from massive gravity in the data set and find that a massless graviton is preferred because of the relatively larger Bayes factor. Without statistically significant evidence for dispersion-related correlations predicted by massive gravity, we place upper limits on the amplitude of the SGWB for graviton mass smaller than $10^{-23}$~eV as $A_{\rm{MG}}<3.21\times 10^{-15}$ at $95\%$ confidence level.