Speaker
Description
One of the most intriguing aspects of strongly coupled quark gluon plasma is near perfect fluidity observed
in relativistic heavy-ion collisions. One way of quantifying this property is by means of the shear viscosity
to entropy density ratio $\eta/s$. Within the AdS/CFT correspondence, it has been conjectured by Kovtun, Son
and Starinets that a universal lower bound $1/4\pi$ exists. We present a new perspective on this matter in the
framework of analogue gravity models, focusing on relativistic fluids with transonic flow. Quantum fluctuations
at the acoustic horizon, the fluid analog of the event horizon of a black hole, result in a thermal radiation of
phonons, the sonic analog of the Hawking radiation. Adopting a covariant relativistic kinetic theory, we describe
the Hawking emission as a dissipative process. Neglecting phonon’s self interactions, we find the saturation
of $\eta/s$. We connect the KSS bound to the absence of a gap in the low energy spectrum of long-wavelength
excitations.
