Garchinger Maier-Leibnitz-Kolloquium: CP conservation in the strong interactions

by Prof. Björn Garbrecht (Physik-Department T70, TUM)

Thursday 24 Apr 2025, 16:15 → 17:15 Europe/Berlin

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

We examine possible effects of the topological theta-term in the QCD-Lagrangian. For the path integral in zero-temperature Euclidean space, topological quantization only emerges in the infinite-volume limit, so that it must be taken prior to summing over winding numbers. This procedure is consistent with the construction of the path-integral contour from steepest-descent flows. As a result, CP violation is absent from observables, in contrast to calculations that rely on singular deformations leading to an inequivalent integration contour with the opposite order of limits. We also address theta-vacua in temporal gauge, which in the conventional picture are not properly normalizable, in contradiction with the axioms of quantum mechanics. However, we show that the possible wave-functionals, given the canonical commutation relations and without introducing extra gauge constraints, are properly normalizable states that do not exhibit CP violation.

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

kolloquium-24-04-25.pdf