196 research outputs found
Constraint on the internal structure of a neutron star from Vela pulsar glitches
Pulsars are spinning extremely rapidly with periods as short as about
milliseconds and delays of a few milliseconds per year at most, thus providing
the most accurate clocks in the Universe. Nevertheless, sudden spin ups have
been detected in some pulsars like the emblematic Vela pulsar. These abrupt
changes in the pulsar's rotation period have long been thought to be the
manifestation of a neutron superfluid permeating the inner crust of neutron
stars. However, the neutron superfluid has been recently found to be so
strongly coupled to the crust that it does not carry enough angular momentum to
explain the Vela data. We explore the extent to which pulsar-timing
observations can be reconciled with the standard glitch theory considering the
lack of knowledge of the dense-matter equation of state.Comment: Proceedings of the conference "The Modern Physics of Compact Stars
2015" held in Erevan, Armenia, from 30 September 2015 to 3 October 2015. To
appear in Proceedings of Scienc
On the Lie subalgebra of Killing-Milne and Killing-Cartan vector fields in Newtonian space-time
The Galilean (and more generally Milne) invariance of Newtonian theory allows
for Killing vector fields of a general kind, whereby the Lie derivative of a
field is not required to vanish but only to be cancellable by some
infinitesimal Galilean (respectively Milne) gauge transformation. In this
paper, it is shown that both the Killing-Milne vector fields, which preserve
the background Newtonian space-time structure, and the Killing-Cartan vector
fields, which in addition preserve the gravitational field, form a Lie
subalgebra.Comment: 8 page
Neutron star crust beyond the Wigner-Seitz approximation
For more than three decades, the inner crust of neutron stars, formed of a
solid lattice of nuclear clusters coexisting with a gas of electrons and
neutrons, has been traditionally studied in the Wigner-Seitz approximation. The
validity of this approximation is discussed in the general framework of the
band theory of solids, which has been recently applied to the nuclear context.
Using this novel approach, it is shown that the unbound neutrons move in the
crust as if their mass was increased.Comment: 8 pages, 2 figures. Proceedings of the International Symposium on
Exotic States of Nuclear Matter, Catania (Italy), June 11-15, 200
Self-interaction errors in nuclear energy density functionals
When applied to a single nucleon, nuclear energy density functionals may
yield a non-vanishing internal energy thus implying that the nucleon is
interacting with itself. It is shown how to avoid this unphysical feature for
semi-local phenomenological functionals containing all possible bilinear
combinations of local densities and currents up to second order in the
derivatives. The method outlined in this Rapid Communication could be easily
extended to functionals containing higher order terms, and could serve as a
guide for constraining the time-odd part of the functional
Superfluid dynamics in neutron star crusts
A simple description of superfluid hydrodynamics in the inner crust of a
neutron star is given. Particular attention is paid to the effect of the
lattice of nuclei on the properties of the superfluid neutrons, and the effects
of entrainment, the fact that some fraction of the neutrons are locked to the
motion of the protons in nuclei
Superfluidity and entrainment in neutron-star crusts
Despite the absence of viscous drag, the neutron superfluid permeating the
inner crust of a neutron star can still be strongly coupled to nuclei due to
non-dissipative entrainment effects. Neutron superfluidity and entrainment have
been systematically studied in all regions of the inner crust of a cold
non-accreting neutron star in the framework of the band theory of solids. It is
shown that in the intermediate layers of the inner crust a large fraction of
"free" neutrons are actually entrained by the crust. The results suggest that a
revision of the interpretation of many observable astrophysical phenomena might
be necessary.Comment: 4 pages, to appear in the proceedings of the ERPM conference, Zielona
Gora, Poland, April 201
Pairing: from atomic nuclei to neutron-star crusts
Nuclear pairing is studied both in atomic nuclei and in neutron-star crusts
in the unified framework of the energy-density functional theory using
generalized Skyrme functionals complemented with a local pairing functional
obtained from many-body calculations in homogeneous nuclear matter using
realistic forces.Comment: 16 pages, 3 figures. Contribution for the book "50 years of nuclear
BCS", edited by R.A. Broglia and V. Zelevinsk
Breathing-mode measurements in Sn isotopes and isospin dependence of nuclear incompressibility
T. Li {\it et al.}[Phys. Rev. C {\bf 81}, 034309 (2010)] have analyzed their
measured breathing-mode energies of some tin isotopes in terms of a first-order
leptodermous expansion, and find for the symmetry-incompressibility coefficient
the value of -550 100 MeV. Removing an approximation that they
made, we find that the first-order estimate of shifts to -661
144 MeV. However, taking into account higher-order terms in the leptodermous
expansion shows that the data are compatible with the significantly lower
magnitudes indicated by both another experiment and some theoretical estimates.Comment: 6 pages, 1 figur
Structure of neutron stars with unified equations of state
We present a set of three unified equations of states (EoSs) based on the
nuclear energy-density functional (EDF) theory.These EoSs are based on
generalized Skyrme forces fitted to essentially all experimental atomic mass
data and constrained to reproduce various properties of infinite nuclear matter
as obtained from many-body calculations using realistic two- and three-body
interactions. The structure of cold isolated neutron stars is discussed in
connection with some astrophysical observations.Comment: 4 pages, to appear in the proceedings of the ERPM conference, Zielona
Gora, Poland, April 201
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