The recent detection of a stochastic signal in the NANOGrav 15-year dataset has aroused
great interest in uncovering its origin. However, the evidence for the Hellings-Downs …

A series of pulsar timing arrays (PTAs) recently observed gravitational waves at the
nanohertz frequencies. Motivated by this remarkable result, we present a novel class of Pati …

Recently, multiple pulsar timing array collaborations have presented compelling evidence
for a stochastic signal at nanohertz frequencies, potentially originating from cosmic strings …

We show that, when connected with monopoles, the flat D-flat direction breaking the local U
(1) BL symmetry as an extension of the minimal supersymmetric standard model can be …

The existence of a stochastic gravitational wave background is indicated by the recent
pulsar timing array (PTA) experiments. We study the enhanced production of second-order …

We discuss E 6 based extensions of the Standard Model (SM) containing two varieties of
superheavy metastable cosmic strings (CSs) that respectively have neutral and electrically …

In a recent paper (Phys. Rev. D 108 (2023) 095053), we have demonstrated that the 2023
PTA results, which hint at a stochastic gravitational wave (GW) background at nanohertz …

We consider F-term hybrid inflation (FHI) and SUSY breaking in the context of a B− L
extension of the MSSM that largely respects a global U (1) R symmetry. The hidden sector …

We revisit the hybrid inflation model within the framework of the Grand Unified Theory (GUT),
focusing on cases where the waterfall phase transition extends over several e-foldings to …

A bstract We present an SO (10) model in which a dimension five operator induces kinetic
mixing at the GUT scale between the abelian subgroups U (1) B− L and U (1) R. We discuss …