42 research outputs found
Ferromagnetism in quark matter
We investigate the magnetic property of the cold quark matter employing the
magnetic moment as the order parameter. Through analysis of the
effective potential , we find that, at relatively high
densities , the quark matter is in the normal phase. At , the magnetic phase transition takes place and, in the low-density
region , the quark matter is in the ferromagnetic phase. For up,
down and strange quarks, , and ( the nuclear density), respectively. We also find that the
leptons ( and ) inside the quark matter are in the normal phase.Comment: 22 pages, 13 figure
Quantum Field Theories in Nonextensive Tsallis Statistics
Within the framework of Tsallis statistics with q ~ 1, we construct a
perturbation theory for treating relativistic quantum field systems. We find
that there appear initial correlations, which do not exist in the
Boltzmann-Gibbs statistics. Applying this framework to a quark-gluon plasma, we
find that the so-called thermal masses of quarks and gluons are smaller than in
the case of Boltzmann-Gibbs statistics.Comment: 16 pages, no figure
Improvement of the hot QCD pressure by the minimal sensitivity criterion
The principles of minimal sensitivity (PMS) criterion is applied to the
perturbative free energy density, or pressure, of hot QCD, which include the
and part of the terms. Applications are made
separately to the short- and long-distance parts of the pressure. Comparison
with the lattice results, at low temperatures, shows that the resultant ``
optimal'' approximants are substantially improved when compared to the
results. In particular, for the realistic case of three quark
flavors, the `` optimal'' approximants are comparable with the lattice results.Comment: 14 pages, 9 figures, LaTe
Angular intricacies in hot gauge field theories
It is argued that in hot gauge field theories, "Hard Thermal Loops" leading
order calculations call for a definite sequence of angular averages and
discontinuity (or Imaginary part prescription) operations, and run otherwise
into incorrect results. The ten years old collinear singularity problem of hot
, provides a striking illustration of that fate.Comment: 14 pages, 1 figur
Two-loop Compton and annihilation processes in thermal QCD
We calculate the Compton and annihilation production of a soft static lepton
pair in a quark-gluon plasma in the two-loop approximation. We work in the
context of the effective perturbative expansion based on the resummation of
hard thermal loops. Double counting is avoided by subtracting appropriate
counterterms. It is found that the two-loop diagrams give contributions of the
same order as the one-loop diagram. Furthermore, these contributions are
necessary to obtain agreement with the naive perturbative expansion in the
limit of vanishing thermal masses.Comment: Latex, 24 pages, postscript figures included with the package
graphic
Self-energy-part resummed quark and gluon propagators in a spin-polarized quark matter and generalized Boltzmann equations
We construct perturbative frameworks for studying nonequilibrium
spin-polarized quark matter. We employ the closed-time-path formalism and use
the gradient approximation in the derivative expansion. After constructing
self-energy-part resummed quark and gluon propagators, we formulate two kind of
mutually equivalent perturbative frameworks: The first one is formulated on the
basis of the initial-particle distribution function, and the second one is
formulated on the basis of `` physical''-particle distribution function. In the
course of construction of the second framework, the generalized Boltzmann
equations and their relatives {\em directly} come out, which describe the
evolution of the system. The frameworks are relevant to the study of a magnetic
character of quark matters, e.g., possible quark stars.Comment: 57 page
On the Light Cone Singularity of the Thermal Effective Expansion
We consider a scalar massless quantum field model, at finite temperature ,
both renormalizable and asymptotically free. Focussing on the singular
structure of the effective perturbation theory about the light cone, several
new insights are put forth, regarding the interplay between hard thermal loop
resummation and the overall compensation of collinear singularities.Comment: 18 page
Proof of a mass singularity free property in high temperature QCD
It is shown that three series of diagrams entering the calculation of some
hot process, are mass (or collinear) singularity free, indeed. This
generalizes a result which was recently established up to the third non trivial
order of (thermal) Perturbation Theory.Comment: 40 pages, 3 figures. to be published in J. Math. Phys. no. 44, 200