Abteilung für Teilchen- & Astroteilchen-Physik

Seminars, Colloquia and Events

Period from 25 July 2024 to 08 August 2024

Thursday, 25 July 2024

  11:15 Kaffeepalaver
Vladimir Yerokhin
QED tests in atomic systems
Central seminar room, library building
Atomic systems with one or several electrons can be calculated very accurately from the first principles of quantum electrodynamics (QED). Comparisons of such ab initio QED calculations with results of high-precision measurements provide stringent tests of bound-state QED theory and deliver determinations of fundamental constants (Rydberg constant, electron mass) and nuclear properties (nuclear charge radii, Zemach radii). In my talk I will discuss the present status of QED tests in Lamb shift, g-factors, and hyperfine splittings in one- and few-electron atoms. We will examine the main challenges in theory that limit the presently achievable accuracy and discuss prospects for future progress.
    ARI Institute Colloquium
Rogemar Riffel
Unveiling the Role of Active Galactic Nuclei Winds in Shaping Galaxies: Impacts on Stellar Populations and Chemical Enrichment
ARI, Moenchhofstrasse 12-14, Seminarraum 1.OG
Identifying and characterizing the processes that transform galaxies from star-forming to quiescent is a fundamental goal of extragalactic astronomy. One critical transformation mechanism is galactic-scale feedback due to active nuclei (AGN). In an ongoing collaboration between Brazil (UFSM - Santa Maria, UFRGS - Porto Alegre and UNIVAP - São José dos Campos) and Germany (ARI - Heidelberg, AIP - Potsdam), our goal is to investigate the impact of AGN feedback in galaxy through the study the properties of multi-gas phase AGN winds, stellar populations, environmental effects, and chemical abundances of AGN hosts. In this talk, I will introduce the collaboration and present previous results obtained by our group. We have been studying the AGN feeding and feedback processes over 15 years, using optical and near-infrared integral field spectroscopy of inner kiloparsec of nearby active galaxies obtained with large telescopes. These observations are used to spatially resolve the molecular and ionized gas emission structure and kinematics. We find that while outflows in ionized gas are seen in most objects studied, in molecular gas they are less common, which usually is dominated by rotation in the disk of galaxies and shows inflows in some cases. The observed ionized outflows are not powerful enough to effectively quench star formation in the AGN host galaxies in most cases.
  16:15 Teilchen-Tee
Julia Harz
Pushing the Limits of Dark Matter: New Approaches and Advanced Methods (Pre-talk 15:30)
Institut für Theoretische Physik, Phil12, SR106
One of the biggest puzzles of astroparticle physics concerns the existence of dark matter (DM). Cosmological data indicates that DM represents around 25% of today's energy content of the Universe, while its nature has not been revealed yet. This talk will focus on DM candidates beyond the standard WIMP paradigm, in particular feebly interacting massive particles (FIMPs). I will highlight new approaches to probe FIMPs embedded in a consistent thermal history after inflation by combining results from collider experiments and cosmological data from PLANCK. At the same time, I will emphasize the importance of including effects of the hot thermal plasma of the early Universe in our theoretical predictions in order to obtain reliable results and hence a correct interpretation of experimental data.

Tuesday, 30 July 2024

  14:15 Kosmologie und Elementarteilchenphysik
Julia Ziegler
CMB hotspots from tachyonic instability of the Higgs potential
Institut für Theoretische Physik, Phil19
At high energies, such as during inflation, the quartic coupling of the Standard Model (SM) Higgs potential runs negative, according to current measurements. This can lead the potential into a tachyonic regime, where the square of the mass of the SM Higgs becomes negative. This tachyonic instability can exponentially enhance Higgs particle production via Hubble-induced effects and via the dynamics of the Higgs field itself. Furthermore the enhanced Higgs particle production can draw energy out of the Higgs field and produce stabilizing thermal corrections. The early produced Higgs particles would then modify the curvature perturbations of the early universe which in turn can cause hot or cold spots on the cosmic microwave background (CMB). The aim of our work is to look into this enhanced Higgs particle production and calculate the temperature of the CMB hotspots, as well as looking into CMB hotspots from other sources such as primordial black holes.

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