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The SEMPARIS seminar webserver hosts annoucements of all seminars taking place in Paris area, in all topics of physics, mathematics and computer science. It allows registered users to receive a selection of announcements by email on a daily or weekly basis, and offers the possibility to archive PDF or Powerpoint files, making it available to the scientific community.   [ More information ]


Seminars this week in series RENC-THEO
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Thursday 20 June 2019, 10:00 at IHP, Salle 314 RENC-THEO (Rencontres Théoriciennes) cond-mat.str-el|hep-th
Anton Kapustin ( Caltech ) Thermal Hall conductance as a relative topological invariant, or detecting gravitational anomalies for lattice systems
Abstract: It is well-known that zero-temperature Hall conductance of a 2d system can be interpreted both as a bulk transport coefficient and a U(1) anomaly for the edge modes. The former interpretation allows one to write down a simple formula for it (Kubo formula). The latter interpretation explains why Hall conductance is a topological invariant. In this talk I will explain the difficulties in extending these considerations to thermal Hall conductance and how they are overcome. I argue that thermal Hall conductance should be regarded as an exact 1-form on the parameter space rather than a function. Another observation is that anomalies of edge modes can be interpreted in physical terms as violations of F. Bloch’s theorem about the absence of currents in an equilibrium state. Combining these observations, I show that low-temperature thermal Hall conductance of a gapped 2d system is robust under arbitrary deformations which do not close the gap.

Thursday 20 June 2019, 11:40 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
David Mateos ( U. Barcelona ) Holography at High Density
Abstract: The physics of Quantum Chromodynamics (QCD) at high density is notoriously difficult to study by conventional methods. Yet this physics will be probed by future observations of gravitational wave signals coming from neutron star mergers. I will discuss what light holography can shed on this difficult regime, paying particular attention to possible crystalline and color superconducting phases.

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