The seminar of the Theory Section takes place Fridays (alternating with the Journal Club) in E3-128 and on zoom, starting normally at 12.15. If you would like to suggest a seminar speaker or want to be added to the email list, please contact the organizer (Michael.Kachelriess@ntnu.no).
A list of seminars in the previous and the current years can be accessed in the sidebar; the (planned) seminars in 2021 are
- 22.01., Marco Stein Muzio (New York University): Closing in on the sources of UHECRs: A multimessenger approach
Abstract: Today ultrahigh energy cosmic rays (UHECRs), with energies in excess of an EeV (or 10^18 eV), provide us with a glimpse both into the most extreme astrophysical environments in the universe and into fundamental interactions beyond LHC energies. However, the source of these particles has long remained a mystery. In this talk, I will focus on progress made in characterizing the sources of UHECRs by combining a phenomenological model of these sources with multimessenger measurements. Recent elaborations of our model have allowed us to make more concrete statements about the types of environments required to explain UHECR data, and possibly astrophysical neutrino data. I will present these constraints and their implications for astrophysical sources.
slides
- 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
Abstract: The theory of cosmic inflation solves the problems of Big Bang cosmology and provides an explanation to the origin of the cosmic microwave background (CMB) radiation. Inflation is often modelled with a scalar field slowly rolling down some potential in FRLW spacetime. In cosmological perturbation theory one perturbs this inflaton field as well as the FRLW metric, and these perturbations can be related to the temperature fluctuations observed in the CMB. In this talk I give an introduction to inflationary cosmology and cosmological correlation functions. I introduce the concept of corrections to these correlation functions and how they can affect the inflationary dynamics. In particular I differentiate between corrections to cosmological observables, i.e. n-point correlation functions, and corrections to the evolving inflaton field and background metric. Corrections to the evolution equations can be viewed as corrections to the slow-rolling parameters, which also enter into observables. - 09.04., Martin Mohajed (NTNU):
- 30.04., Tomas Brauner (UiS):
- 14.05., Magnus Malmquist (NTNU):
Germano Nardini (UiS)
Alexander Stasik (UiO)