Did the nHZ Gravitational Waves Signatures Observed By NANOGrav Indicate Multiple Sector SUSY Breaking?

TL;DR

This paper explores how gravitational wave signals observed by NANOGrav could originate from domain wall collapse caused by multiple sector SUSY breaking, suggesting a low SUSY breaking scale and potential light goldstini.

Contribution

It proposes a novel connection between NANOGrav gravitational wave signals and multiple sector SUSY breaking, highlighting a low SUSY breaking scale as a natural scenario.

Findings

Gravitational waves from domain wall collapse can peak at nHz frequencies.

Low SUSY breaking scale (~1 GeV) is consistent with observed GW signals.

Light goldstini at eV scale may be indicated by the GW observations.

Abstract

Discrete R symmetries always play an important role in low energy SUSY. The spontaneously broken of such discrete R symmetries, for example, by gaugino condensation, can lead to domain walls, which need to be either inflated away or collapse to avoid cosmic difficulties. We propose that explicitly R symmetry violation needed for collapse of domain walls can be the consequence of multiple sector SUSY breaking. The consistency constraints for the generation of non-problematic domain walls from gaugino condensation are discussed. We also study the emitted gravitational waves related to the collapse of domain walls. We find that, for SUSY breaking scale of order ${\cal O}(1)$ ${\rm GeV}$ in one of the sequestered sector (and also a low reheating temperature of order ${\rm MeV}$ if the reheating is not completed when the domain walls collapse), the peak frequency of gravitational waves emitted can lie at nHz. Such a low SUSY breaking scale can be consistency and natural in multiple sector SUSY breaking scenario. The GWs signal by NANOGrav could be a signal of such multiple sector SUSY breaking scenario and it may also indicate the existences of light goldstini at ${\rm eV}$ mass scale.