Talks

The origins of the most energetic particles in the Universe have been a long-standing puzzle. In the quest to identify their sources, it is crucial to understand how these particles are accelerated, how they can escape their production sites, and which roads they can take on their journey to Earth. The multimessenger framework has proven to be a powerful tool for exploring the Universe at these extreme energies.  In this talk I will focus on the triad of (ultra-)high-energy messengers: cosmic rays, neutrinos, and gamma rays. I will begin with a summary of the state of affairs in this field, reviewing some key theoretical developments and recent experimental results. I will then delve into the essential components required for building theoretical models that explain these measurements. Particular emphasis will be placed on modelling the propagation of these messengers, including their interactions with matter and radiation fields, as well as with the poorly understood cosmic magnetic fields. Finally, I will discuss the prospects of building a unified and self-consistent model of the Universe at ultra-high energies and the implications such a model would have for astrophysics, cosmology, and fundamental physics.

The third observing run of advanced LIGO, Virgo and KAGRA brought unprecedented sensitivity towards a variety of quasi-monochromatic, persistent gravitational-wave signals. These signals, called continuous waves, allow us to probe not just the canonical asymmetrically rotating neutron stars, but also different forms of dark matter, thus showing the wide-ranging astrophysical implications of using a relatively simple signal model. In this colloquium, I will first describe the framework within which we try to detect continuous gravitational waves from asymmetrically rotating neutron stars, as well as how we can use these signals to constrain the millisecond pulsar hypothesis for the galactic-center GeV excess. I will then generalize continuous-wave methodologies to include the different forms of dark matter that we could detect using gravitational-wave detectors, specifically: (1) the direct interaction of dark matter with the gravitational-wave detectors themselves; (2) gravitational waves from planetary- or asteroid-mass primordial black hole inspirals and so-called "mini" extreme mass ratio inspirals, and (3) gravitational waves from annihilating boson clouds around spinning black holes.

We are in a new era of gravitational physics in which both gravitational-wave measurements and cosmological observations can be used to test fundamental physics. Moreover, recent computational developments allow us to investigate (at present largely unexplored) regimes where the gravitational force is strong – a very promising area to search for new physics. In this talk I will overview two cases in which we aim to use strong-gravity to learn about the dark components of the universe: the interaction of binary black hole mergers with their dark matter environments and the emission and propagation of scalar gravitational waves, a distinct signature of theories aiming to explain dark energy.

Zoom link:  https://pitp.zoom.us/j/92308918921?pwd=UEk1aEt3bmRxdklqUUpSNlRocldVdz09

Hawking evaporation offers a unique mechanism for particle production, unlike any other process involving fundamental interactions. Moreover, a black hole will emit all existing degrees of freedom in nature, including those which might not interact with the Standard Model sector. Thus, even a small primordial black hole population could have altered different processes in the Early Universe, such as the generation of dark matter, dark radiation, baryon asymmetry or a stochastic gravitational wave background. We will analyse the production of these cosmological observables assuming monochromatic and extended black hole mass and spin distributions, and give prospects on how future observables could test the existence of primordial black holes.

This talk is based on joint work with Owen Gwilliam and Brian Williams. We define factorization homology of factorization envelopes valued in a collection of generalized Weyl modules supported on a cycle in a smooth complex projective variety X. When X is a smooth projective curve, and the cycle a collection of points, we recover the space of coinvariants studied in CFT. 

Zoom link:  https://pitp.zoom.us/j/97473973419?pwd=QjRQUklac2lTRlduSVc3S0FKQW9IQT09