...
- 19.02., Alessandro Mirizzi (INFN, U Bari): Axions: Bounds and Discovery Opportunities
Abstract: Axions have been introduced in relation to the strong CP problem of the QCD and are predicted in many extensions of the Standard Model of particle physics. Depending on the actual value of their mass, axions can play an important role in cosmology, acting as cold or hot dark matter. The coupling with photons allows for axion-photon mixing in external electromagnetic fields. This effect is exploited for direct searches of axions in laboratory experiments. Axions can be searched also through astrophysical observations. Notably they can be produced in stellar cores leading to an excessive energy loss, that would alter the standard stellar evolution. Furthermore, the two-photon vertex would also induce the mixing with axions for photons emitted by distant astrophysical sources, and propagating in the large-scale cosmic magnetic fields, leading to peculiar observational signature. In this talk I will present an overview of current bounds on axions and discovery opportunities in the planned laboratory and astrophysical experiments.
slides - 19.03., Magdalena Eriksson (NTNU, UiS): Quantum corrections to inflation postponed
- 16.04., Martin Mohajed (NTNU): Chiral perturbation theory at finite isospin
Abstract: Chiral perturbation theory (ChiPT) is a low-energy effective field theory of QCD. I will discuss the QCD phase diagram at finite isospin chemical potential and the application of ChiPT to the problem of pion condensation at zero temperature. Since QCD at finite isospin is free of the fermion sign problem, one can use lattice simulations. We compare our two- and three-flavor results for various condensates obtained using ChiPT with recent Monte Carlo data.
slides
- 30.04., Tomas Brauner (UiS): Topology of spontaneous symmetry breaking, emergent higher-form and higher-group symmetries
Abstract: Spontaneous breaking of a continuous global symmetry implies as a rule the existence of new, emergent symmetries, associated with the topology of the vacuum manifold. These may take the form of ordinary symmetries associated to a conserved current and localized charged excitations, or higher-form symmetries, acting on extended topological defects. I will give a brief introduction to the above-mentioned concepts, and then show how higher-form symmetries can be combined into a more general mathematical structure still, referred to as higher-group symmetry. This is a concept that has recently attracted attention in the high-energy theory community. It however turns out to be also relevant for systems as mundane as superfluid mixtures. - 14.05., Magnus Malmquist (NTNU):
...