My talk summarizes the results of several works to assess the prospects of measuring Stochastic GW Background (SGWB) with LISA. After a brief introduction to the topic, I will present some of the expected astrophysical and cosmological SGWBs at LISA scales and discuss the possible implications of their measurement. The last part of my seminar will be devoted to conclusions and future perspectives.
Even if Primordial Black Holes (PBHs) represent only a subdominant component of the dark matter sector, their mere presence can inform us about physical processes that happened at energy scales not reachable by future Particle Physics experiments. Therefore, it is extremely interesting to investigate whether a small fraction of these objects can be detectable by future gravitational wave...
The detection of a subsolar object in a compact binary merger is regarded as one of the smoking gun signatures of a population of primordial black holes (PBHs). We critically assess whether these systems could be distinguished from stellar binaries, for example composed of white dwarfs or neutron stars, which could also populate the subsolar mass range. At variance with PBHs, the...
I will review the several new effects emerging from the combined non-linear action of scalar and tensor modes. Among these: scalar-induced gravitational waves, scalar fluctuation modulation of gravitational waves, anisotropies of the gravitational-wave background induced by large-scale scalar and tensor cosmological inhomogeneities, tensor-induced scalar perturbations. I'll also discuss the...
The theory of inflation provides a mechanism to explain the structures we observe today in the Universe, starting from quantum-mechanically generated fluctuations. However, this leaves the question of: how did the quantum-to-classical transition, occur? During inflation, tensor perturbations interact (at least gravitationally) with other fields, meaning that we need to view these perturbations...
While cooling down, the early universe is believed to have witnessed symmetry breaking phase transitions. With the increasing need to look at beyond the Standard Model theories, one particularly attractive possibility is extending the Standard Model such that phase transitions are of the first order. Not only could they explain e.g. the baryon asymmetry, they are also expected to produce...
Gravitational wave signals from compact binary mergers are of huge interest to the cosmology community due to their ability to act as standard sirens, providing measurements of luminosity distance which are independent of the cosmic distance ladder. Using standard sirens to measure the Hubble constant could shed light on the current tension, which lies above 4σ between early-universe and local...
The ‘spectral siren’ method is a powerful probe of cosmology using gravitational waves observed from compact binary coalescences (CBCs). By exploiting the features of the mass spectrum of CBCs, the degeneracy between mass and redshift can be broken - allowing for the use of such events to constrain cosmological parameters. Previously, these mass spectra have been separated by binary type, with...
Gravitational waves (GWs) induce correlated perturbations to the arrival times of pulses from an array of galactic millisecond pulsars. The expected correlations, obtained by averaging over many pairs of pulsars having the same angular separation (pulsar averaging) and over an ensemble of model universes (ensemble averaging), are described by the Hellings and Downs curve. As shown by Allen...
