Seminar by Marco Finetti (U. Aveiro)

Title: ‘First Order Phase Transitions and Gravitational Waves’

Venue&Time: Red Room / 15:00

Speaker: Marco Finetti (U. Aveiro)

Abstract: The Laser Interferometer Space Antenna (LISA) will be the first space-based gravitational wave (GW) detector, opening a new observational window for both astrophysics and early-Universe cosmology. Operating in the millihertz band, it will probe a rich superposition of GW signals. Astrophysical population models predict a sufficient number of signals in the LISA band to blend together and form an irresolvable Galactic foreground noise. In addition, a stochastic gravitational wave background (SGWB) of cosmological origin could add an unknown component to the measured noise. In this talk, I will assess the bias induced on the parameter estimation of stochastic signals, arising from the unresolved binaries buried within the cosmological signal. Using a representative SGWB model, I will quantify the impact of this effect on the reconstruction of the foreground template parameters and, most importantly, on those of the SGWB model itself. Neglecting inter-template correlations can lead to significan biases, and, for several benchmark cases, those biases exceed the statistical reconstruction uncertainties. These findings expose a key limitation of existing template-based strategies and indicate that unbiased component separation will likely require additional information, such as constraints from resolved sources obtained through global-fit analyses.