Talks

Area metrics define generalized geometric backgrounds to describe spacetime. They are suggested at various places in classical field theory and arise within different approaches to quantum gravity. On these grounds, after introducing the notion of an area metric, I will consider covariant area-metric actions to second order in fluctuations and derivatives. I will then show how these give rise to effective length-metric actions with a distinct nonlocal Weyl-curvature squared term beyond general relativity. Finally, I will point out possible implications and routes for phenomenology.

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.