Running coupling constant from lattice data and bulk viscosity of strange quark matter

Abstract

We study the bulk viscosity of strange quark matter (SQM) in a quasiparticle model at finite chemical potential by extrapolating the previous quasiparticle model of finite temperature lattice QCD. The more proper bulk viscosity coefficient can be given in this model where chemical potential µ and coupling constant g are interdependent. We also apply our result to determine the critical rotation of strange stars by r-mode instability window. Our model is compatible to the millisecond pulsar data for a wide range of mass and radius of the stars.

Bulk viscosity of strange quark matter: Urca versus nonleptonic processes

“…Its value deviates from 1 by at most 28%. This is in qualitative agreement with earlier studies [15][16][17][18][19][20][21][22], neglecting the semileptonic processes.…”

“…This work extends our recent analysis of the bulk viscosity in twoflavor quark matter [14] by including strange quarks. This also augments existing studies of the topic [15][16][17][18][19][20][21][22], in which the role of the Urca processes was not thoroughly investigated.…”

“…Perhaps the best way to appreciate the relative role of the Urca processes is to study the ratio between the complete expression for the bulk viscosity (18) and the commonly used approximate form (23) that takes only the nonleptonic interactions into account. In the more interesting case of parameter set A, this ratio is shown in Fig.…”

“…When an instantaneous departure from chemical equilibrium is induced by expansion/compression of matter, the weak processes try to restore the equilibrium state and, while doing this, reduce the oscillation energy. It is commonly argued that the bulk viscosity in the normal phase of three-flavor quark matter is dominated by the nonleptonic weak processes u d $ u s [15][16][17][18][19][20][21][22]. These are shown diagrammatically in Figs.…”

Medium effects on the surface tension of strangelets in the extended quasiparticle model

“…One can use an analytical expression phenomenologically, such as g(Q/ ) = 4π 3 [18]. One can also apply the µ and T dependence of the approximate running coupling constant in lattice QCD simulations [14,19]. In this paper, we adopt the following approximate expression for the running quantity g(µ) [20,21]:…”