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SUMMARY:Near extremal Black Holes\, extended hydrodynamics  and quantum gr
 avitational effects
DTSTART:20260414T120000Z
DTEND:20260414T140000Z
DTSTAMP:20260502T010800Z
UID:indico-event-51653@agenda.infn.it
DESCRIPTION:Speakers: Elias Kiritsis\n\nCharged asymptotically AdS black h
 oles are known to be dual to strongly coupled QFTs at finite density. In t
 he near-extremal limit\, where temperature is much smaller that the charge
  density \, they are known to develop an IR scaling symmetry encoded in th
 e near horizon AdS2 geometry.\nIt has also been argued that the low energy
  dynamics associated with such black holes\, which is hydrodynamics\, is v
 alid at much higher energies and momenta than what is conventionally assum
 ed. We show concrete evidence of this by comparing exact charge and energy
  correlators to various improved hydrodynamic approximations that resum th
 e effect of non-trivial AdS2 poles  \nWhen the transverse space to the Ad
 S2 geometry has finite volume\, there is a non-zero energy scale Egap\, sc
 aling as 1/charge for large charge\, below which quantum-gravitational cor
 rections due to the fluctuations of the nearly-gapless Schwarzian modes be
 come important. Such corrections to the retarded Green's function are calc
 ulated at different relative values of  the frequency \, T\, and Egap. Th
 e frequency ->  0 limit is used to define the shear viscosity eta. As the
  temperature is lowered below the charge density\, quantum corrections are
  found to increase the value of eta with respect to its famous semiclassic
 al   result  and  the shear viscosity diverges as 1/sqrt{T} at T << Eg
 ap. The quantum result for the ratio eta/s\, where s is the entropy densit
 y\, dips below the semiclassical limit of 1/4 pi when Egap<< T << mu\, the
 n turns back to increase towards lower temperatures\, and finally diverges
  at temperatures much below Egap. \nComments on the similarity of near-ext
 remal black holes and glasses as well as their effect on the Aretakis inst
 ability will be advanced.\n\nhttps://agenda.infn.it/event/51653/
URL:https://agenda.infn.it/event/51653/
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