Several observational phenomena suggest that the standard model of cosmology and
particle physics requires revision. To address this, we consider the extension
of general relativity known as massive gravity (MG). In this Letter, we explore
the imprints of MG on the propagation of gravitational waves (GWs): their
modified dispersion relation and their additional (two vector and one scalar)
polarization modes on the stochastic GW background (SGWB) detected by pulsar
timing arrays (PTAs). We analyze the effects of massive GWs on the Hellings-
Downs curve induced by modification of the overlap reduction function. Our study
consists of analyzing observational data from the NANOGrav 15-year dataset and
the Chinese PTA Data Release I, and is independent of the origin of the SGWB
(astrophysical or cosmological). By considering the bound on the graviton mass
imposed through the dispersion relation, we scrutinize the possibility of
detecting traces of MG in the PTA observational data. We find that massive GWs
predict better fits for the observed pulsar correlations. Future PTA missions
with more precise data will hopefully be able to detect the GW additional
polarization modes and might be effectively used to constrain the graviton mass.
@article{Choi:2025rfr,author={Choi, Chris and Kahniashvili, Tina},title={{Do Pulsar Timing Datasets Favor Massive Gravity?}},eprint={2507.02059},archiveprefix={arXiv},primaryclass={astro-ph.CO},month=jul,year={2025},keywords={General relativity (GR) and modified gravity (MG), Gravitational waves (GWs) theory & observations},url={https://inspirehep.net/literature/2941986},}
2024
Phys. Rev. D
Stochastic gravitational wave background detection using NANOGrav 15-year data set in the context of massive gravity
Chris Choi, Jacob Magallanes, Murman Gurgenidze, and Tina Kahniashvili
Convincing evidence of a stochastic gravitational wave (GW) background has been
found by the NANOGrav Collaboration in the 15-year data set. From this signal,
we can evaluate the possibility of its source being from the early Universe
through the tensor perturbations induced by a massive spin-2 graviton field. We
consider a time-dependent model of the minimal theory of massive gravity and
find values of the graviton mass, mass cutoff time, and Hubble rate of inflation
that amplify the energy spectra of primordial GWs sufficiently to reproduce the
signal from the NANOGrav data within 1-3 standard deviation. However, a
suppression mechanism for high-frequency modes must be introduced to
conservatively obey the big bang nucleosynthesis (BBN) bound. While there are
regions of the parameter space that reproduce the signal, it remains a challenge
to simultaneously respect the BBN and cosmic microwave background bounds without
making the graviton mass cutoff time too deep into the matter-dominated era.
@article{Choi:2023tun,author={Choi, Chris and Magallanes, Jacob and Gurgenidze, Murman and Kahniashvili, Tina},title={{Stochastic gravitational wave background detection using NANOGrav 15-year data set in the context of massive gravity}},eprint={2312.03932},archiveprefix={arXiv},primaryclass={astro-ph.CO},doi={10.1103/PhysRevD.110.063525},journal={Phys. Rev. D},volume={110},number={6},pages={063525},year={2024},keywords={Big-bang-nucleosynthesis (BBN), Cosmic microwave background (CMB), Gravitational waves (GWs) theory & observations, Inflation, Perturbations,General relativity (GR) and modified gravity (MG)},}