Bulk viscosity of gauge theory plasma at strong coupling

Abstract

We propose a lower bound on bulk viscosity of strongly coupled gauge theory plasmas. Using explicit example of the N=2^* gauge theory plasma we show that the bulk viscosity remains finite at a critical point with a divergent specific heat. We present an estimate for the bulk viscosity of QGP plasma at RHIC.

Figures (4)

• Figure 1: Ratio of viscosities $\frac{\zeta}{\eta}$ versus the speed of sound in ${\cal{N}}=2^*$ gauge theory plasma with zero fermionic mass deformation parameter $m_f=0$. The dashed line represents the bulk viscosity bound (\ref{['bulk']}).
• Figure 2: Ratio of viscosities $\frac{\zeta}{\eta}$ in ${\cal{N}}=2^*$ gauge theory plasma near the critical point.
• Figure 3: Ratio of viscosities $\frac{\zeta}{\eta}$ in ${\cal{N}}=2^*$ gauge theory plasma with zero fermionic mass deformation parameter $m_f=0$.
• Figure 4: Ratio of viscosities $\frac{\zeta}{\eta}$ versus the speed of sound in ${\cal{N}}=2^*$ gauge theory plasma with "supersymmetric" mass deformation parameters $m_b=m_f=m$. The dashed line represents the bulk viscosity bound (\ref{['bulk']}). We computed the bulk viscosity up to $m/T\approx 12$. A single point represents extrapolation of the speed of sound and the viscosity ratio to $T\to +0$.