DEPARTMENT OF PHYSICS / HIP JOINT COLLOQUIA / SEMINARS 2026

    • Tuesday 6 October 2026 at 10:15 in A315 and using Zoom: Paul Hoyer (Helsinki)
      Basics of bound states in field theory
      Abstract: Bound states are familiar from the Schrödinger equation of Quantum Mechanics, but less so in QED and QCD. Feynman diagram expansions diverge for soft scattering, signaling the formation of bound states and calling for different methods.
      Gauge theories have instantaneous interactions. According to Dirac (1955), an electron together with its Coulomb field is a gauge invariant state of QED. In A^0=0 gauge the Coulomb field arises from Gauss’ constraint, and is required for full gauge fixing. The instantaneous potential between electrons arises from the interference of their Coulomb fields.
      Confinement in QCD involves a scale ∼ 1 fm, which is not a parameter of the action. Classical scale invariance is broken by renormalization. The MIT Bag Model introduces the scale via a vacuum energy density. The QCD action allows a homogeneous contribution to Gauss’ constraint, which gives an isotropic gluon energy density. Interference between the homogeneous and Coulomb fields results in a confining potential for color singlet qqbar mesons.
    • Tuesday 13 October 2026 at 10:15 in A315 and using Zoom: Juan Pablo Garcés (Heidelberg)
      Asymmetry Sequestering in the Early Universe
      Abstract:       In this seminar, I will present different ways in which “asymmetry sequestering” can be used to explain the matter-antimatter asymmetry of the Universe. After reviewing the necessary ingredients for baryogenesis and the working principle of the sequestering mechanism behind Dirac leptogenesis, I will proceed to tell a four-chapter story. First, we will explore the possibility that our asymmetric Universe originated from the dynamics of a smooth reheating period. Next, we will move beyond the smoothness assumption and see how nonlinear dynamics during preheating can generate an asymmetry, as studied through lattice simulations. In the third chapter, we will see how the “rules of the game” change when replacing some renormalizable operators with higher-dimensional ones. Finally, we’ll ask the question that often comes up in a cosmology seminar: what about dark matter?
    • Tuesday 20 October 2026 at 10:15 in A315 and using Zoom: Roman Zwicky (Edinburgh)
      TBA
      Abstract:       TBA
    • Thursday 22 October 2026 at 10:15 in A315 and using Zoom: Matti Heikinheimo (Helsinki)
      TBA
      Abstract: TBA
    • Tuesday 27 October 2026 at 10:15 in A315 and using Zoom: Débora Mroczek (Turku)
      TBA
      Abstract:       TBA
    • Tuesday 3 November 2026 at 10:15 in A315 and using Zoom: Antti Hippeläinen (Helsinki)
      TBA
      Abstract:       TBA

Hopefully the up to 50 min + 10 min discussion long seminar/colloquium will be understandable to a wide audience.
Contacts: Keijo Kajantie (keijo kajantie at helsinki fi) [ HIP seminar],
Tushar Gupta  (tushar.gupta at helsinki fi) [cosmo seminar]

Other related seminars

Friday 10-12 seminar series in D114: Astrophysics seminar
Mathematical Physics Seminar and Workshop series Wed 14-16 in Exactum C123.
InstituteQ Events and Seminars