315 research outputs found
WIMP Annihilation and Cooling of Neutron Stars
We study the effect of WIMP annihilation on the temperature of a neutron
star. We shall argue that the released energy due to WIMP annihilation inside
the neutron stars, might affect the temperature of stars older than 10 million
years, flattening out the temperature at K for a typical neutron
star.Comment: 20 pages, 2 figure
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
The rigidity of crystalline color superconducting quark matter
We calculate the shear modulus of crystalline color superconducting quark
matter, showing that this phase of dense, but not asymptotically dense,
three-flavor quark matter responds to shear stress like a very rigid solid. To
evaluate the shear modulus, we derive the low energy effective Lagrangian that
describes the phonons that originate from the spontaneous breaking of
translation invariance by the spatial modulation of the gap parameter .
These massless bosons describe space- and time-dependent fluctuations of the
crystal structure and are analogous to the phonons in ordinary crystals. The
coefficients of the spatial derivative terms of the phonon effective Lagrangian
are related to the elastic moduli of the crystal; the coefficients that encode
the linear response of the crystal to a shearing stress define the shear
modulus. We analyze the two particular crystal structures which are
energetically favored over a wide range of densities, in each case evaluating
the phonon effective action and the shear modulus up to order in a
Ginzburg-Landau expansion, finding shear moduli which are 20 to 1000 times
larger than those of neutron star crusts. The crystalline color superconducting
phase has long been known to be a superfluid -- by picking a phase its order
parameter breaks the quark-number symmetry spontaneously. Our results
demonstrate that this superfluid phase of matter is at the same time a rigid
solid. We close with a rough estimate of the pinning force on the rotational
vortices which would be formed embedded within this rigid superfluid upon
rotation. Our results raise the possibility that (some) pulsar glitches could
originate within a quark matter core deep within a neutron star.Comment: 38 pages, 5 figures. v3. Two new paragraphs in Section V
(Conclusion); some additional small changes. A paragraph discussing
supercurrents added in Section I (Introduction). Version to appear in Phys.
Rev.
Superfluid Friction and Late-time Thermal Evolution of Neutron Stars
The recent temperature measurements of the two older isolated neutron stars
PSR 1929+10 and PSR 0950+08 (ages of and yr,
respectively) indicate that these objects are heated. A promising candidate
heat source is friction between the neutron star crust and the superfluid it is
thought to contain. We study the effects of superfluid friction on the
long-term thermal and rotational evolution of a neutron star. Differential
rotation velocities between the superfluid and the crust (averaged over the
inner crust moment of inertia) of rad s for PSR
1929+10 and rad s for PSR 0950+08 would account for their
observed temperatures. These differential velocities could be sustained by
pinning of superfluid vortices to the inner crust lattice with strengths of
1 MeV per nucleus. Pinned vortices can creep outward through thermal
fluctuations or quantum tunneling. For thermally-activated creep, the coupling
between the superfluid and crust is highly sensitive to temperature. If pinning
maintains large differential rotation ( rad s), a feedback
instability could occur in stars younger than yr causing
oscillations of the temperature and spin-down rate over a period of . For stars older than yr, however, vortex creep occurs
through quantum tunneling, and the creep velocity is too insensitive to
temperature for a thermal-rotational instability to occur. These older stars
could be heated through a steady process of superfluid friction.Comment: 26 pages, 1 figure, submitted to Ap
Tkachenko waves, glitches and precession in neutron star
Here I discuss possible relations between free precession of neutron stars,
Tkachenko waves inside them and glitches. I note that the proposed precession
period of the isolated neutron star RX J0720.4-3125 (Haberl et al. 2006) is
consistent with the period of Tkachenko waves for the spin period 8.4s. Based
on a possible observation of a glitch in RX J0720.4-3125 (van Kerkwijk et al.
2007), I propose a simple model, in which long period precession is powered by
Tkachenko waves generated by a glitch. The period of free precession,
determined by a NS oblateness, should be equal to the standing Tkachenko wave
period for effective energy transfer from the standing wave to the precession
motion. A similar scenario can be applicable also in the case of the PSR
B1828-11.Comment: 6 pages, no figures, accepted to Ap&S
Microscopic structure of a vortex line in superfluid neutron star matter
The microscopic structure of an isolated vortex line in superfluid neutron
star matter is studied by solving the Bogoliubov-de Gennes equations. Our
calculation, which is the starting point for a microscopic calculation of
pinning forces in neutron stars, shows that the size of the vortex core varies
differently with density, and is in general smaller than assumed in some
earlier calculations of vortex pinning in neutron star crusts. The implications
of this result are discussedComment: 5 pages, 2 figure
Pulsar Constraints on Neutron Star Structure and Equation of State
With the aim of constraining the structural properties of neutron stars and
the equation of state of dense matter, we study sudden spin-ups, glitches,
occurring in the Vela pulsar and in six other pulsars. We present evidence that
glitches represent a self-regulating instability for which the star prepares
over a waiting time. The angular momentum requirements of glitches in Vela
indicate that at least 1.4% of the star's moment of inertia drives these
events. If glitches originate in the liquid of the inner crust, Vela's
`radiation radius' must exceed ~12 km for a mass of 1.4 solar masses.
Observational tests of whether other neutron stars obey this constraint will be
possible in the near future.Comment: 5 pages, including figures. To appear in Physical Review Letter
Crystalline Color Superconductivity
In any context in which color superconductivity arises in nature, it is
likely to involve pairing between species of quarks with differing chemical
potentials. For suitable values of the differences between chemical potentials,
Cooper pairs with nonzero total momentum are favored, as was first realized by
Larkin, Ovchinnikov, Fulde and Ferrell (LOFF). Condensates of this sort
spontaneously break translational and rotational invariance, leading to gaps
which vary periodically in a crystalline pattern. Unlike the original LOFF
state, these crystalline quark matter condensates include both spin zero and
spin one Cooper pairs. We explore the range of parameters for which crystalline
color superconductivity arises in the QCD phase diagram. If in some shell
within the quark matter core of a neutron star (or within a strange quark star)
the quark number densities are such that crystalline color superconductivity
arises, rotational vortices may be pinned in this shell, making it a locus for
glitch phenomena.Comment: 40 pages, LaTeX with eps figs. v2: New paragraph on Ginzburg-Landau
treatment of LOFF phase in section 5. References added. v3: Small changes
only. Version to appear in Phys. Rev.
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