455 research outputs found
NJL-model description of Goldstone boson condensation in the color-flavor locked phase
A schematic NJL-type model is employed to investigate kaon and pion
condensation in deconfined quark matter in the color-flavor locked (CFL) phase,
explicitly referring to quark degrees of freedom. To that end we allow for
non-vanishing pseudoscalar diquark condensates in addition to the scalar ones
which constitute the CFL phase. Color neutrality is ensured by the appropriate
choice of color chemical potentials. The dependence of the free energy in the
Goldstone condensed phases on quark masses and charge chemical potentials is
found to be in good qualitative -- in most cases also quantitative -- agreement
with the predictions obtained within the effective Lagrangian approach.Comment: 13 pages, 3 figures; v2: slightly extended discussion of interaction
effects including a new curve in Fig.2, to appear in PL
NJL model of homogeneous neutral quark matter: Pseudoscalar diquark condensates revisited
We use a Nambu-Jona Lasinio type model to investigate the phase diagram of
dense quark matter under neutron star conditions in mean field approximation.
The model contains selfconsistently determined quark masses and allows for
diquark condensation in the scalar as well as in the pseudoscalar channel. The
latter gives rise to the possibility of K^0 condensation in the CFL phase. In
agreement with earlier studies we find that this CFLK^0 phase covers large
regions of the phase diagram and that the predominant part of this phase is
fully gapped. We show, however, that there exists a region at very low
temperatures where the CFLK^0 solutions become gapless, possibly indicating an
instability towards anisotropic or inhomogeneous phases. The physical
significance of solutions with pseudoscalar diquark condensates in the 2SC
phase is discussed as well.Comment: 16 pages, 12 figures; v2: minor modifications, version accepted for
publication in PR
Color-Flavor (Un)locking
The structure of the phase diagram of strongly interacting matter at moderate
densities is calculated within a 3-flavor NJL-type quark model with realistic
quark masses. We focus on the influence of the selfconsistently determined
effective strange quark mass on the color-flavor unlocking phase transition.Comment: To appear in the proceedings of the workshop "Ultrarelativistic heavy
ion collisions", Hirschegg 2002, 6 page
Mixed phases of color superconducting quark matter
We examine electrically and color neutral quark matter in beta-equilibrium
focusing on the possibility of mixed phases between different color
superconducting phases. To that end we apply the Gibbs criterion to ensure
phase equilibrium and discuss the external conditions under which these mixed
phases can occur. Neglecting surface and Coulomb effects we find a rich
structure of different mixed phases with up to four components, including 2SC
and CFL matter as well as more ``exotic'' components, like a phase with us- and
ds-pairing but without ud-pairing. Preliminary estimates indicate, however,
that the mixed phases become unstable if surface and Coulomb effects are
included.Comment: 22 pages, 9 figures, v2: minor changes in the text, version to appear
in Nucl. Phys.
Role of two-flavor color superconductor pairing in a three-flavor Nambu--Jona-Lasinio model with axial anomaly
The phase diagram of strongly interacting matter is studied within a
three-flavor Nambu--Jona-Lasinio model, which contains the coupling between
chiral and diquark condensates through the axial anomaly. Our results show that
it is essential to include the 2SC phase in the analysis. While this is
expected for realistic strange quark masses, we find that even for equal up,
down, and strange bare quark masses, 2SC pairing can be favored due to
spontaneous flavor-symmetry breaking by the axial anomaly. This can lead to a
rich phase structure, including BCS- and BEC-like 2SC and CFL phases and new
endpoints. On the other hand, the low-temperature critical endpoint, which was
found earlier in the same model without 2SC pairing, is almost removed from the
phase diagram and cannot be reached from the low-density chirally broken phase
without crossing a preceding first-order phase boundary. For physical quark
masses no additional critical endpoint is found.Comment: 12 pages, 10 figures, added appendix clarifying the relation to
Ginzburg-Landau results, to appear in PR
Inhomogeneous chiral symmetry breaking in dense neutron-star matter
An increasing number of model results suggests that chiral symmetry is broken
inhomogeneously in a certain window at intermediate densities in the QCD phase
diagram. This could have significant effects on the properties of compact
stars, possibly leading to new astrophysical signatures. In this contribution
we discuss this idea by reviewing recent results on inhomogeneous chiral
symmetry breaking under an astrophysics-oriented perspective. After introducing
two commonly studied spatial modulations of the chiral condensate, the chiral
density wave and the real kink crystal, we focus on their properties and their
effect on the equation of state of quark matter. We also describe how these
crystalline phases are affected by different elements which are required for a
realistic description of a compact star, such as charge neutrality, the
presence of magnetic fields, vector interactions and the interplay with
color-superconductivity. Finally, we discuss possible signatures of
inhomogeneous chiral symmetry breaking in the core of compact stars,
considering the cases of mass-radius relations and neutrino emissivity
explicitly.Comment: Invited contribution to the EPJA Topical Issue "Exotic Matter in
Neutron Stars". v2: extended discussion on strange quarks, updated
mass-radius section, other small changes; matches published version. 16
pages, 14 figure
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