12,786 research outputs found
Neutron Stars with Bose-Einstein Condensation of Antikaons as MIT Bags
We investigate the properties of an antikaon in medium, regarding itas a MIT
bag. We first construct the MIT bag model for a kaon with and
in order to describe the interaction of-quarks in hyperonic matter in the
framework of the modifiedquark-meson coupling model. The coupling constant
in the density-dependent bag constant is treated
as afree parameter to reproduce the optical potential of a kaon in asymmetric
matter and all other couplings are determined by usingSU(6) symmetry and the
quark counting rule. With various values ofthe kaon potential, we calculate the
effective mass of a kaon inmedium to compare it with that of a point-like kaon.
We thencalculate the population of octet baryons, leptons and and
theequation of state for neutron star matter. The results show thatkaon
condensation in hyperonic matter is sensitive to the -quarkinteraction and
also to the way of treating the kaon. The mass andthe radius of a neutron star
are obtained by solving theTolmann-Oppenheimer-Volkoff equation.Comment: 14 figure
Medium effects of magnetic moments of baryons on neutron stars under strong magnetic fields
We investigate medium effects due to density-dependent magnetic moments of
baryons on neutron stars under strong magnetic fields. If we allow the
variation of anomalous magnetic moments (AMMs) of baryons in dense matter under
strong magnetic fields, AMMs of nucleons are enhanced to be larger than those
of hyperons. The enhancement naturally affects the chemical potentials of
baryons to be large and leads to the increase of a proton fraction.
Consequently, it causes the suppression of hyperons, resulting in the stiffness
of the equation of state. Under the presumed strong magnetic fields, we
evaluate relevant particles' population, the equation of state and the maximum
masses of neutron stars by including density-dependent AMMs and compare them
with those obtained from AMMs in free space
Effective response theory for zero energy Majorana bound states in three spatial dimensions
We propose a gravitational response theory for point defects (hedgehogs)
binding Majorana zero modes in (3+1)-dimensional superconductors. Starting in
4+1 dimensions, where the point defect is extended into a line, a coupling of
the bulk defect texture with the gravitational field is introduced.
Diffeomorphism invariance then leads to an Kac-Moody current running
along the defect line. The Kac-Moody algebra accounts for the
non-Abelian nature of the zero modes in 3+1 dimensions. It is then shown to
also encode the angular momentum density which permeates throughout the bulk
between hedgehog-anti-hedgehog pairs.Comment: 7 pages, 3 figure
Kaon Condensation in a Neutron Star under Strong Magnetic Fields by Using the Modified Quark-meson Coupling Model
We have considered the antikaon condensation in a neutron star in the
presence of strong magnetic fields by using the modified quark-meson coupling
(MQMC) model. The structure of the neutron star is investigated with various
magnetic fields and different kaon optical potentials, and the effects of the
magnetic fields for kaon condensation is discussed. When employing strong
magnetic fields inside a neutron star with hyperons and kaon condensation, the
magnetic fields can cause the equation of state to be stiff; thus, a large
maximum mass of the neutron star can be obtained.Comment: published in J. Korean Phys.So
Effective mass and decay of in nuclear matter in quark-meson coupling model
The in-medium mass of a \thetaplus, \mtheta^*, in cold symmetric nuclear
matter is calculated by using the quark-meson coupling model. The is
treated as an MIT bag with the quark content . Bag parameters for a
free \thetaplus are fixed to reproduce the observed mass of the \thetaplus.
In doing so, we use three different values of the -quark mass since the mass
of the -quark is not well known. As usual, the strengths of the and
quark couplings to - and -meson fields are determined to fit
the nuclear saturation properties. However, the coupling constant
between the -quark and the -meson cannot be fixed from the
saturation properties, and thus we treat as a free parameter and
investigate how \mtheta^* depends on . %\mtheta^* is calculated
up to 2.5 times the nuclear saturation density, %and we find that We find that
\mtheta^* depends significantly on the value of but not on the
mass of the -quark. Chemical potentials of the and the
system are calculated to discuss the decay of a in nuclear matter.
We calculate the effective mass of a kaon in nuclear matter in two ways; using
the optical potential of in matter and using quark model. By comparing
the effective masses calculated from these two methods, we find the magnitude
of the real part of the optical potential that is consistent with the usual
quark model is about 100 MeV.Comment: 16 pages, 4 figures, 3 table
Field-driven topological glass transition in a model flux line lattice
We show that the flux line lattice in a model layered HTSC becomes unstable
above a critical magnetic field with respect to a plastic deformation via
penetration of pairs of point-like disclination defects. The instability is
characterized by the competition between the elastic and the pinning energies
and is essentially assisted by softening of the lattice induced by a
dimensional crossover of the fluctuations as field increases. We confirm
through a computer simulation that this indeed may lead to a phase transition
from crystalline order at low fields to a topologically disordered phase at
higher fields. We propose that this mechanism provides a model of the low
temperature field--driven disordering transition observed in neutron
diffraction experiments on single crystals.Comment: 11 pages, 4 figures available upon request via snail mail from
[email protected]
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