theoretical physicist
I have presented many seminars throughout the years. This is a list of my favorites. They are accompanied by video recordings, lecture notes, slideshows, etc whenever possible. Seminars are chronologically ordered, with older entries at the bottom of the page.
Abstract: General relativity, electrodynamics, and many other relativistic theories display memory effects. This is a general property of the wave equation itself. In particular, acoustics admits a memory effect. By writing sound in terms of a dual two-form field, we showed how this memory effect can be connected to asymptotic symmetries and a soft theorem.
Tags: infrared physics
Presented at:
Poster: available here (in English)
Related publications:
Abstract: Symmetries are ubiquitous in modern physics. They not only allow for a more simplified description of physical systems but also, from a more fundamental perspective, can be seen as determining a theory itself. In the present paper, we propose a new definition of asymptotic symmetries that unifies and generalizes the usual notions of symmetry considered in asymptotically flat spacetimes and expanding universes with cosmological horizons. This is done by considering BMS-like symmetries for “asymptotic (conformal) Killing horizons”, or A(C)KHs, here defined as null hypersurfaces that are tangent to a vector field satisfying the (conformal) Killing equation in a limiting sense. The construction is theory-agnostic and extremely general, for it makes no use of the Einstein equations and can be applied to a wide range of scenarios with different dimensions or hypersurface cross sections. While we reproduce the results by Dappiaggi, Moretti, and Pinamonti in the case of asymptotic Killing horizons, the conformal generalization does not yield only the BMS group, but a larger group. The enlargement is due to the presence of “superdilations”. We speculate on many implications and possible continuations of this work, including the exploration of gravitational memory effects beyond general relativity, understanding antipodal matching conditions at spatial infinity in terms of bifurcate horizons, and the absence of superrotations in de Sitter spacetime and Killing horizons.
Tags: general relativity, infrared physics, and quantum field theory in curved spacetime
Presented at:
Poster: available here (in English)
Related publications:
Abstract: We studied negative-mass, spherically symmetric stars made of ideal barotropic fluids. After considering linear perturbations away from staticity, we learned that all such models are unstable. Thus, we found a completely classical explanation for the absence of negative masses. While all previous positive mass theorems assume microscopic positivity of mass in some sense, ours does not.
Tags: general relativity and energy conditions
Presented at:
Slideshow: available here (in English, with commentary)
Poster: available here (in English)
Related publications:
Abstract: The memory effect is a prediction in classical general relativity that consists of the fact that, upon the passage of a gravitational wave, a pair of nearby inertial detectors will be permanently displaced. In this seminar, I will review the basic ideas behind the linear memory effect and discuss how it is connected to other infrared aspects of general relativity, such as Weinberg’s soft graviton theorem and the Bondi–Metzner–Sachs group.
Tags: general relativity and infrared physics
Presented at:
Slideshow: available here (in English, with commentary)
Related publications:
Abstract: The functional renormalization group is a powerful tool to study nonperturbative physics, but it has not been much explored within quantum field theory in curved spacetime yet. On the other hand, particle detectors are an omnipresent tool within quantum field theory in curved spacetime and relativistic quantum information but are often treated only perturbatively. In this paper, we present the first computation of the functional renormalization group flow for a particle detector. The chosen model is an inertial Unruh–DeWitt detector in Minkowski spacetime, for simplicity. A new development in heat kernel techniques—the Taylor trick—is necessary to perform the calculations and it is important to carefully choose cutoffs that diverge at the ultraviolet limit to keep the beta functions finite. We compare our results with the MS-bar results at one-loop and find that both computations agree qualitatively, as expected.
Tags: quantum field theory in curved spacetime and functional renormalization group
Presented at:
Slideshow: available here (in English)
Poster: available here (in English)
Related publications: