High Energy Physics

Quasi-sterile neutrinos are a natural consequence of dark sectors interacting with the Standard Model (SM) sector via neutrino- and vector-portals. Essentially, quasi-sterile neutrinos are light dark sector fermions with two generic properties: (i) they mix with the active neutrinos of the SM, and (ii) they are charged under a vector mediator that couples feebly to SM matter. Various interesting phenomenological consequences result from this class of particles. In this talk, I will discuss one such consequence: new, beyond the SM matter effects that can alter in-medium neutrino oscillations. In particular, for special windows of energy and matter densities, active neutrinos can resonantly oscillate into sterile neutrinos. I will discuss how this feature could be exploited to build a quasi-sterile neutrino model that can explain the MiniBooNE and LSND anomalies, while remaining compatible with observations from long-baseline reactor- and accelerator-based neutrino experiments. I will also discuss the implications to this model from the recent MicroBooNE results, and, time permitting, from solar neutrino measurements.

Zoom Link: https://pitp.zoom.us/j/95362454210?pwd=RzNCeDRkMjJXb2xNbHNkcEc1ZTdkUT09

Zoom link:  https://pitp.zoom.us/j/96132106700?pwd=L3ZMOXltZks4Y25abUl5TTdhZTVKUT09

Solar neutrinos are an inevitable background to any dark matter direct detection experiment as they closely mimic the signature of dark matter. In this talk, I will discuss the effects of solar neutrinos on the reach of dark matter-electron scattering experiments, with a focus on semiconductor and xenon-based detectors. In addition, I will present the prospects of measuring and understanding the various solar neutrino components using the same detectors, as well as the effects of non-standard neutrino interactions, thus turning solar neutrinos from a background to an interesting signal in their own right.

I will discuss electromagnetic signals generated by gravitational waves (GWs) in resonant cavity experiments.  Experiments designed for the detection of axion dark matter only need to reanalyze existing data to search for GWs in the GHz range with strains as small as h ∼ 10^{−22} − 10^{−21}. This is still far from the BBN bound on primordial sources, but it is the best direct constraint that we can currently obtain in the laboratory. To get to this result I will correct some long standing misconceptions present in the literature.

Zoom Link: https://pitp.zoom.us/j/94313100053?pwd=bWk1eHh3NWM3NnB1TjR5d0xrY3BIUT09

Since the advent of holography, a lot of progress has been made in our understanding of quantum gravity in AdS. However less is known of its flat space counterpart, even though quantum gravity was certainly first formulated in flat space. Various programs have emerged since, like Celestial Holography or Carrollian Holography, both formulated in four and higher dimensions which is the closest to reality but makes the computation of highly quantum quantities difficult. I will present a 2d model of flat space gravity in which these difficulties can be tackled. This model is dubbed the "Cangemi — Jackiw model" after the authors of arXiv:9203056. It is a model of flat space gravity that can be reformulated in terms of a boundary action whose solutions are Rindler patches. I will explain how this “boundary graviton” reformulation gives access to fully quantum Euclidean results. In particular we will compute the exact spectrum of the Bondi Hamiltonian and show that it can be non-perturbatively completed by a matrix model. I will also comment on scrambling in flat space.

Based on “From black holes to baby universes in CGHS gravity” with Victor Godet (https://arxiv.org/abs/2103.13422) and an upcoming paper with Arjun Kar, Lampros Lamprou and Felipe Rosso.

Zoom Link: https://pitp.zoom.us/j/95709808325?pwd=QVdFUFZiTHVvMWlDb211U3kxQ0ZkZz09

Primordial black holes are a fascinating candidate for the dark matter in the universe. We discuss about their formation in the early universe and evolution across the cosmic history, and focus on their possible detectability at present and future gravitational wave experiments.

In this talk I will consider massless scattering from the point of view of the position, momentum, and celestial bases with a view to advancing a holographic principle for asymptotically flat spacetimes. Within the soft sector, these different languages highlight distinct aspects of the 'infrared triangle': quantum field theory soft theorems arise in the limit of vanishing energy, memory effects are described via shifts of fields along retarded time, and celestial symmetry algebras are realized via currents that appear at special values of the conformal dimension. The latter are determined by the global conformal multiplets in celestial CFT referred to as 'celestial diamonds'. These diamonds degenerate beyond the leading universal soft modes and the standard interpretation of the infrared triangle breaks down: we have neither an obvious asymptotic symmetry nor a Goldstone mode but we do have a soft theorem, and hence a version of a memory effect. I will discuss various aspects of celestial CFT surrounding these Goldstone-like, or Goldilocks, modes and their canonically paired memory modes. They play an important role in constraining celestial OPEs and for understanding the interpretation and implications of the (semi-)infinite tower of tree-level symmetry currents which may pose powerful constraints on consistent low energy effective field theories.

Zoom Link: https://pitp.zoom.us/j/95785822777?pwd=cVJWYVJBS1E3aDJPT1ZSTmlZbzVQQT09

Stimulated decays of axion dark matter, triggered by a source in the sky, could produce a photon flux along the continuation of the line of sight, pointing backward to the source. The strength of this so-called axion “echo” signal depends on the entire history of the source and could still be strong from sources that are dim today but had a large flux density in the past, such as supernova remnants (SNRs). This echo signal turns out to be most observable in the radio band. I will present the sensitivity of radio telescopes such as the Square Kilometer Array (SKA) to echo signals generated by SNRs that have already been observed. In addition, I will show projections of the detection reach for signals from newly born supernovae that could be detected in the future. Intriguingly, an observable echo signal could come from old “ghost” SNRs which were very bright in the past but are now so dim that they haven’t been observed.  

Zoom Link: https://pitp.zoom.us/j/91076203387?pwd=UzNva3N4Zi9mV3BkMlJvUnhtRXRZdz09

Euclidean wormholes are exotic types of gravitational solutions that we still don't understand completely. In the first part of the talk, I will analyze asymptotically AdS wormhole solutions from a gravitational point of view. By studying correlation functions of local and non-local operators, the universal properties that any putative holographic dual should exhibit, become manifest. In the second part, I will describe some concrete field theoretic models (both effective and microscopic) that share these properties.