Speaker
Description
The quark-gluon plasma (QGP) created in heavy-ion collisions possesses a
high degree of momentum-space anisotropy in the local rest frame due to
rapid longitudinal expansion. The degree of momentum-space anisotropy
is largest at early times after the initial nuclear impact, e.g. P_L/P_T
~ 0.2-0.3, and only slowly relaxes toward unity in the center of the
fireball. Additionally, large momentum-space anisotropies persist for
longer and eventually never approach unity as one moves toward the
transverse and longitudinal edges of the QGP. As a consequence,
traditional viscous hydrodynamics approaches which rely on linearization
around an isotropic background can result in particle distribution
functions which violate positivity. In order to address this and other
issues related to the high-degree of QGP momentum-space anisotropy, I
will discuss recent progress in anisotropic hydrodynamics, which is a
reorganization of traditional viscous hydrodynamics that takes into
account momentum-space anisotropies from the outset and guarantees, for
example, positivity of the one-particle distribution function.