Talks

In this class, we will cover basic ecological models on population growth dynamics and saturation, including logistic growth and the Allee effect (cooperative growth). We will see how these models can capture the dynamics of microbial populations, which in turn are convenient experimental models to test hypotheses from ecological theory.

In these lectures, I discuss how GWs are produced by cosmological phase transitions. We start by a short recap of gravitational waves and then move to early attempts using pairs of bubbles and the envelope approximation. Next we cover the energy budget of phase transitions and the impact of sound waves. Finally I comment on recent developments.
 

Compact binary sources detected during the present observing run would last around a few hours in the band of next-generation ground-based gravitational wave detectors. This source observed from an Earth-centered and Earth-rotating frame, will move on the sky. In this talk, we’ll describe a way to use this apparent motion on the sky to measure the speed of gravity and test a wide array of beyond-standard model theories using a phenomenological dispersion relation. We do a full Bayesian parameter estimation on a typical GW170817-like system with higher modes (which should be detectable in future detectors) to measure the speed of gravity and the dispersion relation. I shall also describe how we do this run in a reasonable timeframe and the constraints that we get using one source with signal-to-noise around 1000 and one 40km Cosmic Explorer. The methods developed are fully general and can be used easily for both multiple detectors and detections.

 In this talk I explain a few our works which revolve around the direct an indirect signals of first order cosmological phase transitions. The former consists of the primary gravitational waves created directly from the phase transitions, whereas the later consists of the secondary gravitational waves from the primordial black holes which can originate from the phase transition. These secondary gravitational waves can arise from the primordial black holes from a few different mechanisms such as gravitational interactions, superradiant instability, etc. Furthermore, these primordial black holes can also acquire small initial spin and we focus on their dependence on the phase transition properties.

I will discuss phase transitions in Twin Higgs (TH) models. Previous studies found that phase transitions cannot be first-order. We show that strong first-order phase transitions (FOPTs) can occur provided that appropriate source of Z_2 symmetry breaking between the twin and Standard Model (SM) sectors is present. I will discuss explicit models in which this can be realised. The strongest FOPTs are found in scenarios with large twin fermion Yukawa couplings and light twin sfermions in the framework of supersymmetric TH models. I will present predictions for gravitational waves. I will also discuss the EW symmetry non-restoration scenario in which the EW symmetry breaking occurs at temperatures much above the EW scale and implications for darkogenesis (baryogenesis from dark sector).

In this talk, I will discuss a couple of string theory-inspired models that predict an enhancement of the primordial gravitational wave spectrum during and after inflation. These models offer unique opportunities to probe the physics of the early universe and quantum gravity through potentially detectable signatures in current and future experiments.

First-order phase transitions, which take place when the symmetries are predominantly broken (and masses are then generated) through radiative corrections, produce observable gravitational waves and primordial black holes. I illustrate a model-independent approach that is valid for large-enough supercooling to quantitatively describe these phenomena in terms of few parameters, which are computable once the model is specified.  In particular, in this talk, I describe the abundance, mass and spin of the produced primordial black holes in terms of the above-mentioned parameters. I identify regions of that parameter space allowed by the observational constrains where primordial black holes can account for a fraction of the (or the entire) dark matter abundance.