66 research outputs found
Chiral spiral induced by a strong magnetic field
We study the modification of the chiral phase structure of QCD due to an
external magnetic field. We first demonstrate how the effect of magnetic field
can systematically be incorporated into a generalized Ginzburg-Landau
framework. We then analyze the phase structure in the vicinity of the chiral
critical point. In the chiral limit, the effect is found to be so drastic that
it totally washes the tricritical point out of the phase diagram, bringing the
continent for the chiral spiral. This is the case no matter how small is the
intensity of the magnetic field. On the other hand, the current quark mass
protects the chiral critical point from a weak magnetic field. However the
critical point will eventually be covered by the chiral spiral phase as the
magnetic field grows.Comment: 6 pages, 6 eps figures. Presented at QCD@Work 2016: International
Workshop on QCD - Theory and Experiment, June 27-30, Martina-Franca (Italy
Ginzburg-Landau phase diagram of QCD near chiral critical point - chiral defect lattice and solitonic pion condensate -
We investigate the influence of the isospin asymmetry on the phase structure
of quark matter near the chiral critical point systematically using a
generalized version of Ginzburg-Landau approach. The effect has proven to be so
profound that it brings about not only a shift of the critical point but also a
rich variety of phases in its neighborhood. In particular, there shows up a
phase with spatially varying charged pion condensate which we name the
"solitonic pion condensate" in addition to the "chiral defect lattice" where
the chiral condensate is partially destructed by periodic placements of
two-dimensional wall-like defects. Our results suggest that there may be an
island of solitonic pion condensate in the low temperature and high density
side of QCD phase diagram.Comment: 5 pages, 4 eps figures; v2: version accepted for publication in PL
Polyakov-Nambu-Jona Lasinio model and Color-Flavor-Locked phase of QCD
The effect of Polyakov loop on the QCD phase diagram at high density is
studied within the Nambu-Jona Lasinio model with Polyakov loop (PNJL model). We
point out that the color neutrality is missing in the standard PNJL model at
finite density. Moreover, we discuss how the color-flavor locked (CFL) phase is
to be distorted by the inclusion of Polyakov loop.Comment: 6 pages, 3 eps figures; invited talk at the YITP international
symposium on ``Fundamental Problems in Hot and/or Dense QCD'', Kyoto, Japan,
3-6 Mar 200
Thermal unpairing transitions affected by neutrality constraints and chiral dynamics
We discuss the phase structure of homogeneous quark matter under the charge
neutrality constraints, and present a unified picture of the thermal unpairing
phase transitions for a wide range of the quark density. We supplement our
discussions by developing the Ginzburg-Landau analysis.Comment: 3 pages, 3 plots, contributed to the Proceedings of PANIC'05
(Particles and Nuclei International Conference), Santa Fe, NM, 24-28 October
200
Color Superconductivity in Dense QCD and Structure of Cooper Pairs
The two-flavor color superconductivity is examined over a wide range of
baryon density with a single model. To study the structural change of Cooper
pairs, quark correlation in the color superconductor is calculated both in the
momentum space and in the coordinate space. At extremely high baryon density,
our model becomes equivalent to the usual perturbative QCD treatment and the
gap is shown to have a sharp peak near the Fermi surface due to the
weak-coupling nature of QCD. On the other hand, the gap is a smooth function of
the momentum at lower densities due to strong color magnetic and electric
interactions. The size of the Cooper pair is shown to become comparable to the
averaged inter-quark distance at low densities, which indicates a crossover
from BCS to BEC (Bose-Einstein condensation) of tightly bound Cooper pairs may
take place at low density.Comment: 6 pages, 5 figures. Invited talk at the Joint CSSM/JHF Workshop on
Physics at Japan Hadron Facility (March 14-21, Adelaide, 2002
Baryon formation and dissociation in dense hadronic and quark matter
We study the formation of baryons as composed of quarks and diquarks in hot
and dense hadronic matter in a Nambu--Jona-Lasinio (NJL)--type model. We first
solve the Dyson-Schwinger equation for the diquark propagator and then use this
to solve the Dyson-Schwinger equation for the baryon propagator. We find that
stable baryon resonances exist only in the phase of broken chiral symmetry. In
the chirally symmetric phase, we do not find a pole in the baryon propagator.
In the color-superconducting phase, there is a pole, but is has a large decay
width. The diquark does not need to be stable in order to form a stable baryon,
a feature typical for so-called Borromean states. Varying the strength of the
diquark coupling constant, we also find similarities to the properties of an
Efimov states.Comment: ReVTex 4, 8 pages, 7 figures; accepted version in Phys. Lett.
Thermal Phase Transitions and Gapless Quark Spectra in Quark Matter at High Density
Thermal color superconducting phase transitions in three-flavor quark matter
at high baryon density are investigated in the Ginzburg-Landau (GL) approach.
We constructed the GL potential near the boundary with a normal phase by taking
into account nonzero quark masses, electric charge neutrality, and color charge
neutrality. We found that the density of states averaged over paired quarks
plays a crucial role in determining the phases near the boundary. By performing
a weak coupling calculation of the parameters characterizing the GL potential
terms of second order in the pairing gap, we show that three successive
second-order phase transitions take place as the temperature increases: a
modified color-flavor locked phase (ud, ds, and us pairings) -> a ``dSC'' phase
(ud and ds pairings) -> an isoscalar pairing phase (ud pairing) -> a normal
phase (no pairing). The Meissner masses of the gluons and the number of gapless
quark modes are also studied analytically in each of these phases.Comment: 15 pages, 6 figure
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