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

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.