Garchinger Maier-Leibnitz-Kolloquium: A Systematic Approach to Axion-Production at Finite Density

by Dr Michael Stadlbauer (Physik Department T75, TUM)

Thursday Oct 16, 2025, 4:15 PM → 5:15 PM Europe/Berlin

Lecture Hall, ground floor (west) (LMU building, Am Coulombwall 1, campus Garching)

As an elegant solution to the strong CP problem and promising dark matter candidate, the QCD-axion is one of the best motivated particles beyond the Standard Model (SM). On the phenomenological side, it is extremely predictive as all its couplings to SM-particles as well as its mass is determined by a single scale, the axion decay constant. The hunt for the QCD axion, both with terrestrial experiments as well as astrophysical observables, has exploded in the last years. As of today, astrophysical observations, such as neutron-star cooling and energy loss from supernovae, place the strongest bounds.
In this talk, I will show that astrophysical bounds depend on the momentum-dependence of the axion-nucleon production in finite density environments. This dependence is induced by one-loop corrections that can be systematically calculated within the framework of chiral perturbation theory,
both at finite density and in thermal field theory. As a consequence, the supernova bound is strengthened and the momentum-dependence allows to constrain large parts of parameter space of the axion- neutron coupling. I will report about the current status of this systematic calculation in chiral perturbation theory and elaborate how our findings compare to more phenomenological approaches. Additionally, I will talk about a model-independent axion-production mechanism in supernovae, leading to an orders of magnitude stricter bound than in the current literature.

Hybrid access via ZOOM:
https://lmu-munich.zoom.us/j/98457332925?pwd=TWc3V1JkSHpyOTBPQVlMelhuNnZ1dz09
Meeting ID: 984 5733 2925
Passcode: 979953

 

kolloquium-16-10-25.pdf