Abstract The Laser Interferometer Space Antenna (LISA) has two scientific objectives of
cosmological focus: to probe the expansion rate of the universe, and to understand …

The first direct measurement of gravitational waves by the LIGO and Virgo collaborations
has opened up new avenues to explore our Universe. This white paper outlines the …

We discuss the interpretation of the detected signal by pulsar timing array (PTA)
observations as a gravitational wave background of cosmological origin. We combine …

The existence of nonzero neutrino masses points to the likely existence of multiple Standard
Model neutral fermions. When such states are heavy enough that they cannot be produced …

The North American Nanohertz Observatory for Gravitational Waves has recently reported
strong evidence for a stochastic common-spectrum process affecting the pulsar timing …

In this work, we construct promising model-building routes towards SO (10) grand unified
theory inflation and examine their ability to explain the recent pulsar timing arrays (PTAs) …

Many symmetry breaking patterns in grand unified theories (GUTs) give rise to cosmic
strings that eventually decay when pairs of GUT monopoles spontaneously nucleate along …

The current status of baryogenesis is reviewed, with an emphasis on electroweak
baryogenesis and leptogenesis. The first detailed studies were carried out for SU (5) grand …

The symmetry breaking of grand unified gauge groups in the early Universe often leaves
behind relic topological defects such as cosmic strings, domain walls, or monopoles. For …

We interpret the recent NANOGrav results in terms of a stochastic gravitational wave
background from metastable cosmic strings. The observed amplitude of a stochastic signal …