Theory Seminars SS 22

Thu 28.04.2022, 16.30 h

Ke Fang (U Wisconsin, Madison)

Multi-messenger Astrophysics: Probing Compact Objects with Cosmic Particles

Abstract:
The study of compact objects such as black holes and neutron stars is an important component of modern astrophysics. Recent detections of astrophysical neutrinos, gamma-rays, ultrahigh energy cosmic rays, and gravitational waves open up opportunities to study compact objects with multi-messengers. In this talk, we first review the latest progress in Astroparticle Physics, including some surprising puzzles revealed by new observations of neutrinos and gamma rays. We then demonstrate that the key to Multi-messenger Astrophysics is to understand and establish the link between the messengers. We show that high-energy particle propagation in the vicinity of compact objects may play an important role in connecting multi-wavelength observation and source physics.

Host: P. Mertsch

 

Thu 12.05.2022, 16.30 h

Federico Urban (FZU, Prague)

Harmonic correlators for UHECRs

Abstract:
I will review the applications, advantages and limitations of harmonic techniques to detect anisotropies in the UHECR arrival direction distribution. In particular I will focus on the harmonic cross-correlation between UHECRs and galaxies, where the latter are taken as proxies for the locations of UHECR sources. This type of harmonic cross-correlation shows very promising complementarities with the well-known harmonic UHECR auto-correlation. I will show how the combination of UHECR harmonic auto-correlation and cross-correlations with large-scale structures can disentangle different UHECR primaries and could reverse-engineer some of the effects of the galactic magnetic field to a much better degree than the auto-correlation alone. I will conclude with an outlook on applications to other data sets, such as astrophysical neutrinos.

Host: J. Lesgourgues

 

Thu 19.05.2022, 16.30 h (MBP2 117)

Ramon Winterhalder (CP3, UC Louvain)

Targeting Multi-Loop Integrals with Neural Networks

Abstract:
Achieving high-precision in HEP theory predictions requires the evaluation of scattering amplitudes beyond leading order. These (multi)-loop amplitudes can contain complicated integrals where an analytic solution is not feasible. In this case, they have to be evaluated numerically, and a careful treatment of possible singularities of the integrand is required. After isolating and factorizing the UV and IR poles of the integrand, using sector decomposition, only threshold singularities remain, which can be avoided by a deformation of the integration contour into the complex plane. While valid contours are easy to construct, the numerical precision for a multi-loop integral can depend critically on the chosen contour. We present methods to optimize this contour using a combination of optimized, global complex shifts and a normalizing flow. These methods can lead to a significant gain in precision.

Host: C. Brancaccio

 

Thu 02.06.2022, 16.30 h

Carmelo Evoli (GSSI, L'Aquila)

TBA

Host: P. Mertsch

 

Thu 30.06.2022, 16.30 h

Irene Tamborra (NBI Kopenhagen)

TBA

Host: S. Manconi

 

Thu 07.07.2022, 16.30 h

Sven Heinemeyer (UA Madrid)

TBA

Host: R.Harlander

 

Thu 14.07.2022, 16.30 h

Vivian Poulin (U. Of Montpellier)

TBA

Host: J. Lesgourgues