Regularization dependence of the OTOC. Which Lyapunov spectrum is the physical one?
06.06.2019 14:30 – 15:30
Abstract: In this talk I will study the contour dependence of the out-of-time-ordered correlation function (OTOC) both in weakly coupled field theory and in the Sachdev-Ye-Kitaev (SYK) model. I will show that the OTOC, including its Lyapunov spectrum, depends sensitively on the shape of the complex time contour in generic weakly coupled field theories. I will then show that for gapless theories with no thermal mass, such as SYK, the Lyapunov spectrum turns out to be an exception; their Lyapunov spectra do not exhibit contour dependence, though the OTOCs do. These results put into question which of the Lyapunov exponents computed from the exponential growth of the OTOC reflects the actual physical dynamics of the system. I will argue that, in a weakly coupled Phi^4 theory, a kinetic theory argument indicates that the symmetric configuration of the time contour, namely the one for which the bound on chaos has been proven, has a proper interpretation in terms of dynamical chaos. Finally, I will show a relation between the OTOCs and a quantity which may be measured experimentally: the Loschmidt echo. [ arXiv: 1903.09595 ]
Lieu
Bâtiment: Ecole de Physique
Auditoire 234
Organisé par
Département de physique théoriqueIntervenant-e-s
Aurelio Romero-Bermudez, Leiden Universityentrée libre
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