Seminar by Rome Samanta (SSM and INFN Naples): “Topological-defect searches in the mHz (LISA) band”

Title: “Topological-defect searches in the mHz (LISA) band”

Speaker: Rome Samanta (SSM and INFN Naples)

Venue & Time: Red Room | 15:00-16:00

Abstract: Topological defects, such as domain walls and cosmic strings, generically arise in a wide range of field-theory and particle-physics models. One of their most intriguing features is their potential to produce stochastic gravitational-wave backgrounds. If formed in the early Universe, these defects can generate broad-band gravitational-wave spectra whose present-day signatures may fall within the sensitivity ranges of current experiments, such as LIGO and pulsar timing arrays (PTAs), as well as upcoming detectors including LISA, the Einstein Telescope (ET), and DECIGO. In this talk, I will discuss the prospects for detecting gravitational-wave signals from topological defects in the LISA frequency band. Although the mHz band is particularly promising for probing early-Universe physics, it is also expected to contain several astrophysical stochastic backgrounds. Identifying a cosmological signal in the presence of these foregrounds and backgrounds is therefore a nontrivial inference problem. In the first half of the talk, I will introduce the basic theory of topological defects and discuss Bayesian methods for signal characterization and parameter inference using LISA simulations. In the second half, I will focus on the detection prospects for one particular class of defects, domain walls, and one of their variants, highlighting their characteristic gravitational-wave signatures and the challenges involved in distinguishing them from astrophysical backgrounds.