Domain Wall Network: A Dual Solution for Gravitational Waves and Hubble Tension?

TL;DR

This paper investigates whether domain wall networks can simultaneously explain the stochastic gravitational wave background observed in pulsar timing data and alleviate the Hubble tension, proposing a dual solution with specific parameter ranges.

Contribution

It introduces a model linking domain wall parameters to gravitational wave signals and Hubble tension, providing analytical relationships and observational constraints.

Findings

Domain wall tension around (29-414 TeV)^3 can explain gravitational wave background.

Decay of particles from domain walls into dark radiation can ease Hubble tension.

Constraints on wall tension and decay temperature if domain walls are not the source.

Abstract

We explore the possibility that domain wall networks generate the stochastic gravitational wave background (SGWB) observed as a strong common power-law process in the Data Release-2 of Parkes Pulsar Timing Array. We find that a broad range of parameters, specifically wall tension around $\sigma_{\textrm{DW}} \sim (29-414 , \textrm{TeV})^3$ and wall-decay temperature within $T_d \sim 20-257 , \textrm{MeV}$, can explain this phenomenon at a $68\%$ credible level. Meanwhile, the same parameters could ease the Hubble tension if particles from these domain wall networks decay into dark radiation. We establish a direct analytical relationship, $\Omega_{\textrm{GW}}(f_p,T_0) h^2 \sim \Omega_{\textrm{rad}} h^2 ( \Omega_\nu \Delta N_{\textrm{eff}})^2$, to illustrate this coincidence, underlining its importance in the underlying physics and potential applicability to a wider range of models and data. Conversely, if the common power-law process is not attributed to domain wall networks, our findings impose tight limits on the wall tension and decay temperature.