GWs from PTs and PTAs by Thomas Konstandin

Program: Hearing beyond the standard model with cosmic sources of Gravitational Waves
ORGANIZERS: Koushik Dutta (IISER Kolkata, India), Tathagata Ghosh (HRI, India), Anish Ghoshal (University of Warsaw, Poland) and Subhendra Mohanty (IIT Kanpur, India)
DATE & TIME: 30 December 2024 to 10 January 2025
VENUE: Ramanujan Lecture Hall
The experimental detection of gravitational waves (GWs) due to the merger of astrophysical objects like black holes and neutron stars is one of the biggest discoveries in physics. The GWs can also be sourced from several other cosmological phenomena, and their amplitudes and frequencies vary in a wide range. The detection of these gravitational waves can potentially probe fundamental physics beyond the Standard Model (BSM) of particle physics and cosmology.
For example, inflation is associated with several sources of tensor perturbations during inflation and the ones generated during reheating and preheating. Each of these propagates as detectable Stochastic GW background (SGWB) signals. Associated with inflation is also the collapse of density fluctuations to form Primordial Black Holes (PBH), leaving signatures in induced GWs and non-gaussianities. Cosmological first-order Phase Transitions (PT) during which the universe transitions from a false vacuum to a true vacuum leads to bubble nucleation, growth, and and their merger. This is another source of SGWB. GWs are also produced from the decays of topological defects like cosmic strings and domain walls, etc. Detection of all these potential sources of GWs will help us probe very high-scale physics which may be otherwise impossible to reach in terrestrial or astroparticle physics experiments. In the meantime, NANO-Grav, InPTA and other PTA collaborations have announced the first evidence of the detection of SGWB based on their 15 years of data.
We aim to discuss all these possibilities of detecting SGWB sourced by cosmological and BSM physics and explore their multiband searches in the context of these observed events. In addition, we will explore how gravitational wave signals may reveal possible modifications of general relativity. With these aims in mind, the workshop will bring together experts in particle physics, cosmology, and the gravitational wave community.
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