Quark number susceptibilities at high temperatures

Abstract

We calculate second and fourth order quark number susceptibilities for 2+1 flavor QCD in the high temperature region. In our study we use two improved staggered fermion formulations, namely the highly improved staggered quark formulation, and the so-called p4 formulation, as well as several lattice spacings. Second order quark number susceptibilities are calculated using both improved staggered fermion formulations, and we show that in the continuum limit the two formulations give consistent results. The fourth order quark number susceptibilities are studied only using the p4 formulation and at non-zero lattice spacings. We compare our results on quark number susceptibilities with recent weak coupling calculations, and find that these agree reasonably well with the lattice calculations within the estimated uncertainties.Comment: RevTeX, 9 pages, 5 figures, the discussion of the comparison with the perturbative results is revised and the conclusion about the validity of the perturbative approaches is modified, published versio

Electrical conductivity and charge diffusion in thermal QCD from the lattice

“…(4.8). Our results appear consistent with the findings of other lattice groups [53,54] and also with resummed perturbation theory [60], in particular concerning the deviation from unity at the highest temperatures.…”

“…Susceptibilities show a rapid rise in the crossover region: at low temperature they are small since quarks are confined; at high temperature they are larger and they approach the ideal gas limit. They have been studied by many groups in the past [49][50][51][52][53][54]. Notably, so far, lattice studies have mainly employed staggered fermions.…”

Equation of state in (2+1)-flavor QCD

“…This is, to some extent, expected as at such high temperatures, i.e., at small a, all the above actions should have small cutoff effects. This expectation has been demonstrated in the calculations of quark-number susceptibilities [32]. In Sec.…”

“…We have used it extensively to carry out high precision studies of the chiral and deconfinement aspects of the QCD transition which lead to the estimate T c = 154 (9) MeV for the QCD transition temperature. It has also been used to study the fluctuations of conserved charges [7,[30][31][32] and various spatial and temporal correlation functions [33,34]. The study of fluctuations of conserved charges at high temper-atures demonstrates, in particular, that the HISQ action is indeed very effective in reducing cutoff effects [32].…”

Finite Temperature ($\mu=0$)

“…A recent calculation of the second (in the continuum) and fourth (at several cutoffs) order quark number susceptibilities indicates reasonable agreement with weak-coupling expansions for T 400 MeV [53], given the uncertainties of the latter. However, more work is needed for controlling the cutoff effects and taking the continuum limit for the fourth-order susceptibilities at high temperature.…”