Phase Transitions and the Perfectness of Fluids

Abstract

We calculate the ratio η/s, the shear viscosity (η) to entropy density (s), which characterizes how perfect a fluid is, in weakly coupled real scalar field theories with different types of phase transitions. The resulting η/s behaviors agree with the empirical observations in atomic and molecular systems such as H 2 O, He and N. These behaviors are expected to be the same in N component scalar theories with an O(N ) symmetry. We speculate these η/s behaviors are general properties of fluid shared by QCD and cold atoms. Finally, we clarify some issues regarding counterexamples of the conjectured universal bound η/s ≥

Temperature dependent transport coefficients in a dynamical holographic QCD model

“…It has been proposed by the authors of [61] to use the shear viscosity over entropy density ratio as a signal of the critical end point(CEP). It has also been shown that η/s is suppressed near the critical temperature in the semi quark gluon plasma [62], and a cusp, a jump at T c and a shallow valley around T c in η/s can characterize first-, second-order phase transitions and crossover [63]. If the perturbative calculation based conclusion in [64] that small η/s implies large jet quenching parameter can be extended to strong coupled region, then we can expect that the temperature dependence behavior of jet quenching parameter can also contain the information of phase transition.…”

Transport coefficients from extremal Gauss-Bonnet black holes

“…All known materials in nature by now satisfy this bound. More discussions on the universality and the bound can be found in [21,22,23,24,25,26,27,28,29].…”

Oscillations at low energies

“…The main goal of the SNO + experiment [37], placed in the SNOLAB in Canada, is the measurement of the neutrino-less double-beta decay (0ν − ββ) by means of 0.3% loading of scintillator with 800 kg of 130 Te (using natural Te) planned for spring 2016. The detec-tor will be filled with water in spring 2015, while with 1 kton of LAB scintillator in fall 2015.…”