S.P. Klevansky

Thermodynamics of a quark - meson plasma in the Nambu-Jona-Lasinio model

Abstract We investigate the thermodynamics of a quark-meson plasma in the two-flavour Nambu-Jona-Lasinio (NJL) model. We calculate the thermodynamic functions to order 1 N c in an expansion in the inverse number of colours, which is seen to include mesonic exchange. After discussing the bound and resonant states that occur, and the associated scattering phase shifts, we compute their contribution to the behaviour of the thermodynamic potential and the bulk thermodynamic quantities that follow from this, such as entropy and energy densities. In the chiral limit, the chiral phase-transition line is calculated in the ( μ -T) plane; the transition is of first order at low temperature and of second order at high temperature, for zero chemical potential. The crossing point is at T = 78 MeV. As is expected physically, the mesonic or collective degrees of freedom play a dominant role at low temperature, while the quark degrees of freedom are most relevant at high temperature. In keeping with the fact that the NJL model is not confining, we see that a mixed phase exists. For μ = 0, it lies in the temperature range80 ⩽ T ⩽ 140MeV. Other thermodynamic quantities of interest, such as the chiral and quark susceptibilities are also calculated, but in the mean-field approximation only, since they are unaltered by the inclusion of fluctuations about the mean field, to the level of approximation made.

Phase diagram and bulk thermodynamical quantities in the Nambu - Jona-Lasinio model at finite temperature and density

We reexamine the recent instanton motivated studies of Alford, Rajagopal, and Wilczek, and Berges and Rajagopal in the framework of the standard SU(2) Nambu\char21{}Jona-Lasinio (NJL) model. The chiral phase diagram is calculated in the temperature-density plane, and the pressure is evaluated as the function of the quark density. Obtaining simple approximate relations describing the T-\ensuremath{\mu} and

π-π scattering lengths at finite temperature

T\ensuremath{-}{p}_{F}

ππ scattering in the ϱ-meson channel at finite temperature

phase transition lines, we find that the results of the instanton based model and that of the NJL model are identical. The diquark transition line is also given.

Coupled Oscillator Systems Having Partial PT Symmetry

Abstract The s -wave π-π scattering lengths a 1 ( T ) at finite temperature T and isospin I = 0,2 are calculated within the SU (2) Nambu-Jona-Lasinio model. a 2 ( T ) displays a singularity at the Mott temperature T M , defined as m π ( T M ) = 2 m q ( T M ), while a 0 ( T ) is singular in addition at the lower temperature T d , where m σ ( T d ) = 2 m π ( T d ), m ρ and m π being the masses of the σ and π mesons, respectively. Numerically we find T d = 198 MeV and T M = 215 MeV. We speculate on possible experimental consequences.

PT -Symmetric Representations of Fermionic Algebras

Abstract We study ππ scattering in the I = 1, JP = 1− channel at finite temperature in the framework of the extended Nambu-Jona-Lasinio model that explicitly includes vector and axial-vector degrees of freedom in addition to the usual scalar and pseudoscalar sector. The S-matrix in the coupled channels q q and ππ is constructed via ϱ-exchange in the s-channel. The self-energy of the ϱ-meson contains both quark and pion loop contributions. The analytic structure of the S-matrix for T ⩾ 0 is investigated and the motion of the ϱ-pole as a function of coupling constant and temperature is followed in the complex √s-plane. For numerical calculations, parameters are chosen in order that mπ, ƒ π and the experimental ππ phase shifts δ11 at zero temperature are reproduced, and then the behavior of the ϱ-pole as well as the ππ cross section is investigated as a function of the temperature. We find that the position of the ϱ mass stays practically constant for 0 ⩽ T ⩽ 130 MeV, and then moves down in energy by about 200 MeV for 130 MeV ⩽ T ⩽ 230 MeV.

Soft deconfinement — critical phenomena at the Mott transition in a field theory for quarks and mesons

This paper examines chains of

Nonunique C operator in PT quantum mechanics

N

Elastic scattering and transport coefficients for a quark plasma in SUf(3) at finite temperatures

coupled harmonic oscillators. In isolation, the

Hadronization cross-sections at the chiral phase transition of a quark plasma☆

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