SEMESTER 2025 - SUMMER
04.03.2025
Andreas Trautner
CFTP, IST, University of Lisbon
Electroweak scale hierarchy from conformal and custodial symmetry
I will introduce the idea of "Custodial Naturalness" to explain the origin of the electroweak scale hierarchy. Custodial Naturalness is based on classical scale invariance as well as an extension of the Standard Model (SM) scalar sector custodial symmetry to SO(6). This requires a single new complex scalar field charged under a new U(1) gauge symmetry which partially overlaps with B-L. Classical scale invariance and the high-scale scalar sector custodial symmetry are radiatively broken by quantum effects that generate a new intermediate scale by dimensional transmutation. The little hierarchy problem is solved because the Higgs boson arises as pseudo-Nambu-Goldstone boson of the spontaneously broken SO(6) custodial symmetry. The minimal realization of Custodial Naturalness has the same number of parameters as the SM and predicts testable new physics in the form of a heavy Z' as well as a light but close-to invisible dilaton. Simple extensions furthermore allow to explain neutrino masses and Dark Matter - only in a region of parameter space that can be completely excluded by future colliders.
Slides
18.03.2025
Kodai Sakurai
Tohoku University
Primordial black hole formation by inverted bubble collapse
A primordial black hole (PBH) is one of the promising candidates for dark matter. PBHs can form when significant density perturbations are generated in the early Universe. Various mechanisms for producing overdense regions that lead to PBH formation have been proposed in the literature. Many of these mechanisms postulate that such an overdense region has spherical symmetry; however, in general, deviations from a perfect sphere can occur, making PBH formation nontrivial. In this talk, we discuss a novel mechanism for PBH formation in which the generated overdense region maintains spherical symmetry. We also demonstrate that the observed microlensing events in the OGLE and Subaru HSC data can be explained by applying this new mechanism to extended Higgs models.
01.04.2025
Werner Porod
Univeristy of Würzburg
13.05.2025
Stefan Lederer
Technische Universität München
10.06.2025
Dominik Stöckinger
TU Dresden