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 …

We provide a review on the state-of-the-art of gravitational waves induced by primordial
fluctuations, so-called induced gravitational waves. We present the intuitive physics behind …

Pulsar timing arrays (PTAs) have reported evidence for a stochastic gravitational wave (GW)
background at nanohertz frequencies, possibly originating in the early Universe. We show …

Pulsar timing arrays gathered evidence of the presence of a gravitational wave background
around nHz frequencies. If the gravitational wave background was induced by large and …

We perform a Bayesian analysis of NANOGrav 15-yr and IPTA DR2 pulsar timing residuals
and show that the recently detected stochastic gravitational-wave background is compatible …

In the recent years, primordial black holes (PBHs) have emerged as one of the most
interesting and hotly debated topics in cosmology. Among other possibilities, PBHs could …

Cosmological gravitational particle production (CGPP) is the creation of particles in an
expanding universe due solely to their gravitational interaction. These particles can play an …

Detection of a gravitational-wave signal of non-astrophysical origin would be a landmark
discovery, potentially providing a significant clue to some of our most basic, big-picture …

We discuss cosmic domain walls described by a tension redshifting with the expansion of
the Universe. These melting domain walls emit gravitational waves with the low-frequency …

Models that produce axionlike particles (ALPs) after cosmological inflation due to
spontaneous U (1) symmetry breaking also produce cosmic-string networks. Those axionic …