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Résumé |
Holographic duality has helped us paint a robust picture of transport in infinitely strongly coupled theories. In the first part of my talk, I will present a series of results that arose from studies of higher-derivative theories of gravity and that have provided us with a new picture of thermal physics at finite coupling. For a wide range of physical phenomena, these results interpolate between what was previously known from holography at infinite coupling and weakly coupled perturbative quantum field theories. Such phenomena include an explicit mechanism for restricting the validity of hydrodynamics through the emergence of massive, long-lived modes (quasihydrodynamics), delayed hydrodynamisation of quark-gluon plasma, the presence of quasiparticle excitations, formation of branch cuts in thermal correlators and a transport peak in thermal spectral functions. In the second part of my talk, I will discuss a recently discovered property of hydrodynamics and of microscopic quantum many-body chaos—"pole-skipping". This phenomenon, which remains valid in the presence of stringy corrections, allows for a precise analytic connection between resummed, all-order hydrodynamics and the properties of quantum chaos (the Lyapunov exponent and the butterfly velocity). At weak coupling, the existence of pole-skipping is unknown, although a new kinetic theory formulation of quantum chaos also clearly connects analytic properties of collective hydrodynamics with microscopic, molecular chaos even at weak coupling. |
