118 research outputs found
Color-magnetic flux tubes in quark matter cores of neutron stars
We argue that if color-superconducting quark matter exists in the core of a
neutron star, it may contain a high density of flux tubes, carrying flux that
is mostly color-magnetic, with a small admixture of ordinary magnetic flux. We
focus on the two-flavor color-superconducting ("2SC") phase, and assume that
the flux tubes are energetically stable, although this has not yet been
demonstrated. The density of flux tubes depends on the nature of the transition
to the color-superconducting phase, and could be within an order of magnitude
of the density of magnetic flux tubes that would be found if the core were
superconducting nuclear matter. We calculate the cross-section for
Aharonov-Bohm scattering of gapless fermions off the flux tubes, and the
associated collision time and frictional force on a moving flux tube. We
discuss the other forces on the flux tube, and find that if we take in to
account only the forces that arise within the 2SC core region then the
timescale for expulsion of the color flux tubes from the 2SC core is of order
10^10 years.Comment: 28 pages, LaTeX, 1 figure, 2 appendices; added discussion of
energetic stability of flux tube
Damping of differential rotation in neutron stars
We derive the transport relaxation times for quasiparticle-vortex scattering
processes via nuclear force, relevant for the damping of differential rotation
of superfluids in the quantum liquid core of a neutron star. The proton
scattering off the neutron vortices provides the dominant resistive force on
the vortex lattice at all relevant temperatures in the phase where neutrons
only are in the paired state. If protons are superconducting, a small fraction
of hyperons and resonances in the normal state would be the dominant source of
friction on neutron and proton vortex lattices at the core temperatures K.Comment: 5 pages, Revtex, Phys. Rev. D 58, Rapid Communication, in pres
BCS approximation to the effective vector vertex of superfluid fermions
We examine the effective interaction of nonrelativistic fermions with an
external vector field in superfluid systems. In contrast to the complicated
vertex equation, usually used in this case, we apply the approach which does
not employ an explicit form of the pairing interaction. This allows to obtain a
simple analytic expression for the vertex function only in terms of the order
parameter and other macroscopic parameters of the system. We use this effective
vertex to analyze the linear response function of the superfluid medium at
finite temperatures. At the time-like momentum transfer, the imaginary part of
the response function is found to be proportional to the fourth power of small
Fermi velocity, i.e. the energy losses through vector currents are strongly
suppressed. As an application, we calculate the neutrino energy losses through
neutral weak currents caused by the pair recombination in the superfluid
neutron matter at temperatures lower than the critical one for S-wave pairing.
This approach confirms a strong suppression of the neutrino energy losses as
predicted in Ref.[4].Comment: 19 pages, no figure
Fluctuations of the Color-superconducting Order Parameter in Heated and Dense Quark Matter
Fluctuations of the color superconducting order parameter in dense quark
matter at finite temperatures are investigated in terms of the phenomenological
Ginzburg - Landau approach. Our estimates show that fluctuations of the
di-quark gap may strongly affect some of thermodynamic quantities even far
below and above the critical temperature. If the critical temperature of the
di-quark phase transition were rather high one could expect a manifestation of
fluctuations of the di-quark gap in the course of heavy ion collisions.Comment: 12
Constraining hypernuclear density functional with -hypernuclei and compact stars
We present a simultaneous calculation of heavy single- hypernuclei
and compact stars containing hypernuclear core within a relativistic density
functional theory based on a Lagrangian which includes the hyperon octet and
lightest isoscalar-isovector mesons which couple to baryons with
density-dependent couplings. The corresponding density functional allows for
SU(6) symmetry breaking and mixing in the isoscalar sector, whereby the
departures in the - and - couplings away from
their values implied by the SU(3) symmetric model are used to adjust the theory
to the laboratory and astronomical data. We fix - coupling
using the data on the single- hypernuclei and derive an upper bound on
the - from the requirement that the lower bound on the maximum
mass of a compact star is .Comment: 10 pages, 4 figures, to appear in Phys. Lett. B, v2: minor editorial
correction
Spatially inhomogeneous condensate in asymmetric nuclear matter
We study the isospin singlet pairing in asymmetric nuclear matter with
nonzero total momentum of the condensate Cooper pairs. The quasiparticle
excitation spectrum is fourfold split compared to the usual BCS spectrum of the
symmetric, homogeneous matter. A twofold splitting of the spectrum into
separate branches is due to the finite momentum of the condensate, the isospin
asymmetry, or the finite quasiparticle lifetime. The coupling of the isospin
singlet and triplet paired states leads to further twofold splitting of each of
these branches. We solve the gap equation numerically in the isospin singlet
channel in the case where the pairing in the isospin triplet channel is
neglected and find nontrivial solutions with finite total momentum of the
pairs. The corresponding phase assumes a periodic spatial structure which
carries a isospin density wave at constant total number of particles. The phase
transition from the BCS to the inhomogeneous superconducting phase is found to
be first order and occurs when the density asymmetry is increased above 0.25.
The transition from the inhomogeneous superconducting to the unpaired normal
state is second order. The maximal values of the critical total momentum (in
units of the Fermi momentum) and the critical density asymmetry at which
condensate disappears are and . The possible
spatial forms of the ground state of the inhomogeneous superconducting phase
are briefly discussed.Comment: 13 pages, including 3 figues, uses RevTeX; minor corrections, PRC in
pres
Neutrino radiation from dense matter
This article provides a concise review of the problem of neutrino radiation
from dense matter. The subjects addressed include quantum kinetic equations for
neutrino transport, collision integrals describing neutrino radiation through
charged and neutral current interactions, radiation rates from pair-correlated
baryonic and color superconducting quark matter.Comment: 11 pages, 5 figures. Based in part on lectures delivered at the
Summer school "Dense Matter In Heavy Ion Collisions and Astrophysics", BLTP,
Joint Institute for Nuclear Research, Dubna, Russia. The complete lectures
are available online at http://theor.jinr.ru/~dm2006/talks.html v2: matches
published versio
Direct Urca neutrino rate in colour superconducting quark matter
If deconfined quark matter exists inside compact stars, the primary cooling
mechanism is neutrino radiation via the direct Urca processes d->u+e+antinu_e
and u+e->d+nu_e. Below a critical temperature, T_c, quark matter forms a colour
superconductor, one possible manifestation of which is a condensate of
quark Cooper pairs in an electric-charge neutralising background of electrons.
We compute the neutrino emission rate from such a phase, including charged
pair-breaking and recombination effects, and find that on a material
temperature domain below T_c the pairing-induced suppression of the neutrino
emission rate is not uniformly exponential. If gapless modes are present in the
condensed phase, the emissivity at low temperatures is moderately enhanced
above that of completely unpaired matter. The importance of charged current
pair-breaking processes for neutrino emission both in the fully gapped and
partially gapped regimes is emphasised.Comment: 5 pages, 2 figures; to appear in Phys. Rev. C (Rapid Comm.
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