A number of challenges to the standard Λ CDM model have been emerging during the past
few years as the accuracy of cosmological observations improves. In this review we discuss …

Gravitational wave (GW) detection in space probes the GW spectrum that is inaccessible
from the Earth. In addition to the LISA project led by the European Space Agency, and the …

Multiple pulsar timing array (PTA) collaborations recently announced the evidence of
common-spectral processes caused by gravitational waves (GWs). These can be the …

Gravitational waves (GWs) have a great potential to probe cosmology. We review early
universe sources that can lead to cosmological backgrounds of GWs. We begin by …

A bstract Gravitational waves (GWs) from strong first-order phase transitions (SFOPTs) in the
early Universe are a prime target for upcoming GW experiments. In this paper, I construct …

Axions comprise a broad class of particles that can play a major role in explaining the
unknown aspects of cosmology. They are also well-motivated within high energy physics …

A stochastic background of gravitational waves could be created by the superposition of a
large number of independent sources. The physical processes occurring at the earliest …

We present a new frequency-domain phenomenological model of the gravitational-wave
signal from the inspiral, merger and ringdown of nonprecessing (aligned-spin) black-hole …

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 …

In this paper we discuss the anatomy of frequency-domain gravitational-wave signals from
nonprecessing black-hole coalescences with the goal of constructing accurate …