Carl-G. Källman

Mean-field QCD model for hot/dense matter

Abstract Perturbative estimates of thermodynamical quantities relevant for ultra-relativistic collisions of heavy nuclei are found unreliable and some recent effective models for hot and dense QCD matter are found to have very little in common with QCD. A mean-field model, resembling QCD and yielding qualitatively correct results, is suggested and discussed.

Possible solution to the plasmon puzzle in hot SU(N) gluon matter

Abstract We present a calculation of the plasmon contribution to the thermodynamical potential for hot SU( N ) gluon matter in the temporal axial gauge. This result together with a recent non-perturbative calculation of the colour-electric gluon mass in the same gauge leads to a modified plasmon contribution which is always smaller than the g 2 -contribution, thus resolving the plasmon puzzle.

Instanton effects in the equation of state for dense neutron star matter

Abstract Vacuum fluctuation effects in QCD due to instantons are considered in dense neutron star matter. In the density region of interest to neutron star cores we find a density dependence ∼n − 1 3 B , in contrast to a result by Shuryak, ∼ n − 5 3 B .

What lattice calculations can tell us about the gluon gas

Higher order perturbative and nonperturbative corrections to the grand potential of hot QCD are considered qualitatively Comparing with lattice results, it is argued that the nonperturbative parts are small but that the O(g4) term in Ω is large and positive.

Symmetry breaking in superdense matter

Abstract A gauge theory for superdense matter is considered. It is shown that in the mean-field approximation at T = 0 °K the symmetry breaking increases with increasing density. The state of dense matter and the early Universe are shortly discussed.

On the quark-hadron transition in the early universe

Abstract The quark-hadron transition in the early universe is discussed. Perturbative and non-perturbative QCD calculations are compared to an effective interaction approach. It is found that the transition should take place around T ≅ 250 MeV, but there is not much information on the order of the transition. Non-adiabatic effects are shortly discussed.

Note on the neutron matter-quark matter transition

Abstract Superdence matter is considered within QCD and an extended Higgs model. Instanton effects are estimated and found to affect the neutron matter-quark matter phase transition only slightly.

Instanton contribution to the color-magnetic mass in hot QCD

Abstract Instanton contributions to the color-magnetic mass are estimated at high temperature. They are found to be small compared to the perturbatively estimated contribution.

The critical energy density for quark-gluon matter formation in nucleus-nucleus collisions at extremely relativistic energies

Abstract We estimate T c , μ c and ϵ c for the transition from hadronic matter to quark-gluon matter. We find that μ = 0 ϵ c ≅ 0.6 GeV fm −3 with T c ≅ 160 MeV, whereas ϵ c increases with baryon number density to ϵ c ≅ 1.2 GeV fm −3 at μ c ≅ 600 MeV for T = 0. Our results are discussed with special emphasis on nucleus-nucleus collisions at extremely relativistic energies.

A U(1) symmetric equation of state for dense matter

Abstract A U(1) symmetric gauge model for dense matter is presented. At high density the free gas result p = ϵ 3 is obtained.