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HIP seminar room A315

  • Tuesday 19 September 2017 at 10.15 in A315: Paolo Di Vecchia (Nordita)
    Universal soft behavior of massless particles and the tale of two dilatons
    Abstract: One of the important consequences of symmetries is to determine the low-energy behavior of massless particles. In this talk I will show how gauge invariance fixes the soft behavior of massless particles as photons, gluons, gravitons, dilatons and Kalb-Ramond field. I then will check these results in string theory and show that the subsubleading behaviour for gravitons includes string corrections in the bosonic and heterotic strings. This is the consequence of the fact that the three-graviton vertex has string corrections with respect to the field theoretical one obtained from the Einstein-Hilbert action. It turns out instead that the soft behavior of the string dilation has no string corrections and, in particular, involves the generators of dilatations and special conformal transformations. I will then study the soft behavior of the Goldstone boson, called in the literature also dilaton, that one gets when one breaks spontaneously conformal invariance and I will show that its soft behavior is very similar, but not identical, to that of the string dilaton.

  • Tuesday 26 September 2017 at 10.15 in A315: Oliver Gould (Imperial College, London)
    Magnetic monopole creation
    Abstract: Elementary magnetic monopoles have never been experimentally observed but there are credible theoretical reasons to believe that they may nonetheless exist. For one, their presence would imply the observed quantisation of electric charge. In this talk, I give a partial answer to the questions: if magnetic monopoles do exist, can we create them? And if so, how? Many experiments have tried to create magnetic monopoles in the collision of “small” particles, such as protons. I outline serious, though inconclusive, theoretical doubts that such collisions could ever lead to magnetic monopole pair production, even at arbitrarily high energies. On the other hand, I show that sufficiently light magnetic monopoles may be efficiently produced in heavy ion collisions, such as the lead-lead collisions at the Large Hadron Collider.

  • Tuesday 3 October 2017 at 10.15 in A315: Hiren Patel (UMass Amherst)
    Abstract: TBA

  • Tuesday 10 October 2017 at 10.15 in A315: Tomas Brauner (Stavanger)
    Nuclear matter without nucleons and Bose-Einstein condensation in strong magnetic fields
    Abstract: Topological soliton lattices are known in condensed-matter physics, for instance in liquid crystals or chiral magnets. In this talk, I will argue that a similar structure appears also in dilute nuclear matter. Sufficiently strong magnetic fields destabilize ordinary nuclear matter and lead to the formation of a chiral soliton lattice (CSL) of neutral pions. This is a model-independent result based on low-energy effective field theory, and the magnetic fields and baryon densities required may occur in the cores of neutron stars. The spectrum of excitations above the CSL ground state contains a soft, nonrelativistic mode that gives an anomalous contribution to pressure, scaling with temperature and magnetic field as T^{5/2}B^{3/2}. Finally, I will argue that in stronger but still achievable magnetic fields, the neutral pion CSL background may catalyze Bose-Einstein condensation of charged pions.

  • Tuesday 31 October 2017 at 10.15 in A315: Emilia Kilpua and Minna Palmroth (Helsinki)
    Abstract: TBA

  • Thursday 30 November 2017 at 10.15 in A315: Xiaoyong Chu (Vienna)
    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) [department / HIP seminar],
Francesco Montanari (francesco montanari at helsinki fi) [cosmo seminar]

Other related seminars

Friday 10-12 seminar series in D117: Astrophysics seminar.
Mathematical Physics Seminar and Workshop series Wed 14-16 in Exactum C123.