Gravitation

The landmark detection of a gravitational wave (GW) from the Binary Neutron Star Merger (BNS) GW170817 and its electromagnetic counterparts allowed us to study the Universe in an entirely new way. Among the several discoveries made possible by GW170817, we can find the tightest constraints on the speed of gravity and the measurement of the Hubble constant (H0). Both of these measurements were made thanks to several assumptions and conditions that might not hold for future detections.

The small-scale physics of inflation can leave unique observational signatures in the gravitational wave background and may also generate primordial black holes as a dark matter candidate. These phenomena often involve a significant enhancement of inflationary fluctuations, potentially leading to the breakdown of standard perturbation theory. In this talk, I will discuss how lattice simulations provide a crucial tool for addressing these challenges.

One of the major predictions of Einstein’s general relativity is gravitational lensing, the deflection or amplification of light by mass distributions. In my talk, I focus on gravitational wave lensing in wave optics (very long wavelength), as opposed to the standard geometric optics. I show how a supermassive black hole acts as a wave optics lens, for triple systems in in the regime of the LISA mission.

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Dark compact objects are nowadays routinely observed through multiple experimental schemes. Measurements of their vibrational spectra offer unprecedented opportunities to investigate the highly dynamical regime of General Relativity, search for signs of new physics, and increase the evidence for their "black hole nature".

Over the past 8 years, Advanced LIGO and Advanced Virgo have detected about 90 gravitational-wave (GW) events, all of them produced by the coalescence of a compact binary system (CBC). In addition to CBCs, new types of GW signals are expected to be observed in the near future, as the sensitivity and observing time of GW detectors increase. Among them, we refer to long-duration transients as GW signals whose duration in the frequency band of the detectors ranges from few seconds to hours.

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We are now routinely detecting gravitational waves (GW) emitted by
merging black holes and neutron stars. Those are the afterlives of
massive stars that formed all across the Universe - at different times
and with different metallicities.
Birth metallicity plays an important role in the evolution of massive
stars.
Consequently, the population properties of mergers are sensitive to the
metallicity dependent cosmic star formation history (fSFR(Z,z)).

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