Abstract:

The inflationary paradigm, already in its simplest disguises, has been spectacularly successful when it comes to agreement with observations. However, there’s a lot we do not yet know about inflation:

- what is its energy scale?

- how about its particle content?

- how did inflation begin?

…

New cosmological probes (at all scales, from CMB to interferometers) will soon put some...

The search for primordial gravitational waves through their imprint on the polarization of the CMB is one of the most promising avenues for new discoveries in cosmology. The next generation of measurements will be carried out by ground-based facilities, which must face a number of observational challenges. In this talk I will review the current state of the art and discuss the main strategies...

GW170817 with its coincident optical counterpart led to a first "standard siren" measurement of the Hubble constant independent of the cosmological distance ladder. The Schutz "statistical" method with galaxy catalogues, which is expected to work in the absence of uniquely identified hosts, has also started bringing in its first estimates. In this talk we report the latest results of the...

The groundbreaking progresses in the detection of gravitational waves, and the possibility to gain insight into the black holes that populate our Universe, have recently attracted attention on the proposal of Primordial Black Holes, which could constitute the dark matter. If such objects were generated during the early stages of the cosmological history, they would be accompanied by a...

We present the computation of the spin of primordial black holes produced by the collapse of large inhomogeneities in the early universe. Since such primordial black holes originate from overdensity peaks, we resort to peak theory to obtain the probability distribution of the spin at formation. We show that the spin is a first-order effect in perturbation theory: it results from the action of...

Current observational constraints leave only a few mass ranges for the primordial black holes (PBHs) to be the totality of dark matter in the universe.

One of them is around $10^{-12}$ solar masses. If PBHs with this mass are formed due to an enhanced scalar-perturbation amplitude, their formation is inevitably accompanied by the generation of gravitational waves (GWs) with frequency peaked...

Although Cosmic Microwave Background and Large Scale Structure probe the largest scales of our universe with ever increasing precision, our knowledge about the smaller scales is still very limited other than the bounds on Primordial Black Holes(PBHs). We show that the statistical properties of the small scale quantum fluctuations can be probed via the stochastic gravitational wave background,...

We explore gravitational wave signals arising from first-order phase transitions occurring in a secluded hidden sector, allowing for the possibility that the hidden sector may have a different temperature than the Standard Model sector. We present the sensitivity to such scenarios for both current and future gravitational wave detectors in a model-independent fashion. Since secluded hidden...

The effects of gravitational waves on the arrival times of pulses from pulsars produce a characteristic angular correlation in the pulsar timing residuals. It is still not understood, however, whether the local GW signal due to super massive black hole (SMBH) mergers will be the type of stochastic background that arises as the sum of a large number of cosmological sources, or whether it will...

Microlensing of gravitational waves by can result in interference patterns in the observed strain. The spècific form of these interference patterns depend on the mass of the microlens and the abundance of microlenses. We demonstrate how microleneses with masses of a few tens of solar masses (similar to the masses of the black holes observed by LIGO-Virgo) can produce observable effects in the...

I will discuss recent collaborative studies on the potential of advanced GW detectors for improving the current knowledge of cosmological parameters and testing the dark-energy sector, using standard sirens. We consider second generation network made by the two advanced LIGO detectors+advanced Virgo+LIGO India+Kagra, and third-generation detectors such as the Einstein Telescope and Cosmic...

Independently of the order of the phase transition, topology of the defects, and nature, global or gauge, of the symmetry broken, defect networks emit gravitational waves (GWs). In this talk I will review how any scaling defect network emits an irreducible GW background, which has scale-invariant amplitude for $f\gg f_{\rm eq}$. I will show results of numerical experiments where we compute,...

The stochastic gravitational wave background (SGWB) expected from cosmic string loops contains relevant information on the properties of the string network itself. In this talk, we analyze the ability of the Laser Interferometer Space Antenna (LISA) to measure this background under different hypothesis, determining the relevant parameter information that can be extracted from it.

Although in the Standard Model the electroweak phase transition is a crossover, many well-motivated extensions can generate a first-order phase transition at the electroweak scale. For a sufficiently strong phase transition, LISA would be able to observe gravitational waves sourced by plasma motion generated by expanding and colliding bubbles. While numerical simulations have examined ‘weak’...

We revisit the effects of an early matter dominated era on gravitational waves induced by scalar perturbations. We carefully take into account the evolution of the gravitational potential, the source of these induced gravitational waves, during a gradual transition from an early matter dominated era to the radiation dominated era, where the transition timescale is comparable to the Hubble time...

We study gravitational waves induced from the primordial scalar perturbations at second order around the reheating of the Universe. We consider reheating scenarios in which a transition from an early matter dominated era to the radiation dominated era completes within a timescale much shorter than the Hubble time at that time. We find that an enhanced production of induced gravitational waves...

Although Weakly Interacting Massive Particles (WIMPs) are promising candidates of dark matter, null results from various experiments cast doubt on WIMPs, implying the need to search for other candidates. Ultralight scalar fi?eld is one of the other dark matter candidates that is motivated by string theory. Interestingly, if it couples with Standard Model particles, it oscillates mirrors in...

The astrophysical stochastic gravitational-wave background is created by incoherent superposition of sources, such as merging binary black holes and binary neutron stars. The estimated merger rate of binary compact objects suggests that this background may be detected with ongoing and future gravitational-wave experiments. In this talk I will describe the theoretical predictions for the...