2,011 research outputs found
Neutrinos in dense quark matter and cooling of compact stars
We discuss that observational constraints on neutrino cooling processes may
restrict the spectrum of quark matter phases admissible for compact star
interiors.Comment: 3 pages, contribution to International School of Nuclear Physics on
"Neutrinos in Cosmology, in Astro-, Particle- and Nuclear Physics,
Erice-Sicily, September 16-24, 200
A New Approach to Non-Commutative U(N) Gauge Fields
Based on the recently introduced model of arXiv:0912.2634 for non-commutative
U(1) gauge fields, a generalized version of that action for U(N) gauge fields
is put forward. In this approach to non-commutative gauge field theories, UV/IR
mixing effects are circumvented by introducing additional 'soft breaking' terms
in the action which implement an IR damping mechanism. The techniques used are
similar to those of the well-known Gribov-Zwanziger approach to QCD.Comment: 11 pages; v2 minor correction
Modern compact star observations and the quark matter equation of state
We present a hybrid equation of state (EoS) for dense matter that satisfies
phenomenological constraints from modern compact star (CS) observations which
indicate high maximum masses (M = 2 M_sun) and large radii (R> 12 km). The
corresponding isospin symmetric EoS is consistent with flow data analyses of
heavy-ion collisions and a deconfinement transition at approx. 0.55 fm^{-3}.
The quark matter phase is described by a 3-flavor Nambu--Jona-Lasinio model
that accounts for scalar diquark condensation and vector meson interactions
while the nuclear matter phase is obtained within the
Dirac-Brueckner-Hartree-Fock (DBHF) approach using the Bonn-A potential. We
demonstrate that both pure neutron stars and neutron stars with quark matter
cores (QCSs) are consistent with modern CS observations. Hybrid star
configurations with a CFL quark core are unstable.Comment: 16 pages, 4 figures; published version, important note added in proo
Neutrino emissivities and bulk viscosity in neutral two-flavor quark matter
We study thermodynamic and transport properties for the isotropic
color-spin-locking (iso-CSL) phase of two-flavor superconducting quark matter
under compact star constraints within a NJL-type chiral quark model. Chiral
symmetry breaking and the phase transition to superconducting quark matter
leads to a density dependent change of quark masses, chemical potentials and
diquark gap. A self-consistent treatment of these physical quantities
influences on the microscopic calculations of transport properties. We present
results for the iso-CSL direct URCA emissivities and bulk viscosities, which
fulfill the constraints on quark matter derived from cooling and rotational
evolution of compact stars. We compare our results with the phenomenologically
successful, but yet heuristic 2SC+X phase. We show that the microscopically
founded iso-CSL phase can replace the purely phenomenological 2SC+X phase in
modern simulations of the cooling evolution for compact stars with color
superconducting quark matter interior.Comment: 15 pages, 6 figures, references added, text improve
Pseudoscalar Meson Nonet at Zero and Finite Temperature
Theoretical understanding of experimental results from relativistic heavy-ion
collisions requires a microscopic approach to the behavior of QCD n-point
functions at finite temperatures, as given by the hierarchy of Dyson-Schwinger
equations, properly generalized within the Matsubara formalism. The convergence
of sums over Matsubara modes is studied. The technical complexity of
finite-temperature calculations mandates modeling. We present a model where the
QCD interaction in the infrared, nonperturbative domain, is modeled by a
separable form. Results for the mass spectrum of light quark flavors (u, d, s)
and for the pseudoscalar bound-state amplitudes at finite temperature are
presented.Comment: 14 pages, 11 figures, accepted for publication in Physics of
Particles and Nuclei Letters, based on invited lectures at "Dense Matter In
Heavy Ion Collisions and Astrophysics", 21.08-01.09 2006, Dubna, Russi
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