DEPARTMENT OF PHYSICS / HIP JOINT COLLOQUIA / SEMINARS
HIP seminar room A315
- Tuesday 2 October 2018 at 10.15 in A315: Kazuo Fujikawa (RIKEN)
Chiral anomaly and Berry’s phase
Abstract: Recently, chiral anomaly and Berry’s phase are often used in the study of chiral properties of condensed matter and nuclear physics. In my talk I first suggest to define adiabatic Berry’s phase precisely following the original ideas of Berry and Simon such that its topology arises from the singularity associated with the level crossing phenomenon. This definition covers most of the popular examples of Berry’s phase such as Stone’s model and the model of Xiao,Shi and Niu, but their validity domains are severely limited. Part of the freedom of the “monopole” associated with Berry’s adiabatic phase is frozen compared to the conventional monopole, and we suggest the term “adiabatic monopole”. A well-defined monopole is not derived from an adiabatic monopole. This limitation implies that the derivation of anomalous commutators of spatial coordinates from an adiabatic monopole associated with Berry’s phase is not justified. As a result, the derivation of anomalous charge non-conservation from the anomalous commutators of spatial coordinates in the literature is not valid, besides the covariant gauge anomaly thus derived does not satisfy the “anomaly matching condition”.
- Tuesday 9 October 2018 at 10.15 in A315: Shinsuke Kawai (Suwon, Korea)
Gauss-Bonnet Chern-Simons gravitational wave leptogenesis
Abstract: The gravitational Chern-Simons term coupled to an evolving axion is known to generate lepton number through the gravitational anomaly. We examine this leptogenesis scenario in the presence of the Gauss-Bonnet term over and above the gravitational Chern-Simons term. We find that the lepton production can be exponentially enhanced. The Gauss-Bonnet term creates CP-violating instability of gravitational waves that may appear transiently after inflation, and during the period of instability elliptically polarized gravitational waves are exponentially amplified at sub-horizon scales. This instability does not affect the spectrum of the cosmic microwave background as it occurs at much shorter length scales. In a typical scenario based on natural inflation, the observed baryon asymmetry of the Universe corresponds to the UV cutoff scale at 10^14−16 GeV.
- Tuesday 30 October 2018 at 10.15 in A315: Djuna Croon (TRIUMF)
- Thursday 8 November 2018 at 10.15 in A315: Ulf Danielsson (Uppsala)
Reflections on the dS swampland
Abstract: A review of recent claims that there are no de Sitter vacua in string theory. What are the consequences for dark energy and the multiverse?
- Tuesday 13 November 2018 at 10.15 in A315: Michael Ramsey-Musolf (UMass Amherst)
- Tuesday 20 November 2018 at 10.15 in A315: Jonathan Braden (University College London)
A New Real-Time Picture of Vacuum Decay
Abstract: Quantum decay of false vacuum states via the nucleation of bubbles may have played an important role in the early history of our Universe. For example, in multiverse models that utilize false vacuum eternal inflation, the Big Bang of our observable Universe corresponds to one of these bubble nucleation events. Further, our observable Universe may have undergone a series of symmetry-breaking first-order phase transitions as it cooled, which may have produced a remnant background of gravitational waves.
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]
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