The talk will be given remotely:
Topic: Israeli joint seminar - Madge/Gouttenorie
Time: Nov 4, 2020 11:00 AM Jerusalem
Join Zoom Meeting
https://technion.zoom.us/j/91033490160?pwd=OXJXUWVObWJYNWRRVVpxbTB1OGpCdz09
Meeting ID: 910 3349 0160
Passcode: Hep_joint
Eric will talk about
Constraining Secluded Hidden Sectors with Gravitational Waves
Abstract:
Thermal hidden sectors with particles at sub-MeV scales are subject to constraints from the effective number of neutrino species, which require these sectors to decouple from the Standard Model and to be colder than the photon bath around and after the epoch of Big Bang Nucleosynthesis. We discuss how this affects cosmological first-order phase transitions and the corresponding stochastic gravitational wave background in such a hidden sector. We demonstrate that is possible to construct models that comply with the constraints and still produce a gravitational wave signal that is detectable via future pulsar timing experiments.
Yann will talk about
String Fragmentation in Supercooled Confinement and implications for Dark Matter
Abstract:
A strongly-coupled sector can feature a supercooled confinement transition in the early universe. When fundamental quanta of the strong sector are swept into expanding bubbles of the confined phase, the distance between them is large compared to the confinement scale. The flux linking the fundamental quanta then deforms and stretches towards the wall, producing an enhanced number of composite states upon string fragmentation. The composite states are highly boosted in the plasma frame, which leads to additional particle production through the subsequent deep inelastic scattering. I will discuss the modelling of these dynamics and introduce the consequences for the abundance and energetics of particles in the universe and for bubble-wall Lorentz factors. As a case of study, I will show that the composite dark matter relic density is affected by many orders of magnitude. | 
