Statut  Confirmé 
Série  RENCTHEO 
Domaines  condmat.strel,hepth 
Date  Jeudi 20 Juin 2019 
Heure  10:00 
Institut  IHP 
Salle  Salle 314 
Nom de l'orateur  Kapustin 
Prenom de l'orateur  Anton 
Addresse email de l'orateur  
Institution de l'orateur  Caltech 
Titre  Thermal Hall conductance as a relative topological invariant, or detecting gravitational anomalies for lattice systems 
Résumé  It is wellknown that zerotemperature 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 1form 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 lowtemperature thermal Hall conductance of a gapped 2d system is robust under arbitrary deformations which do not close the gap. 
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