1,926 research outputs found
Neutrino Interactions in Octet Baryon Matter
Neutrino processes caused by the neutral current are studied in octet baryon
matter. Previous confusion about the baryonic matrix elements of the neutral
current interaction is excluded, and a correct table for them improved by
consideration of the proton spin problem is presented instead.Comment: 6 page
Finite-size effects at the hadron-quark transition and heavy hybrid stars
We study the role of finite-size effects at the hadron-quark phase transition
in a new hybrid equation of state constructed from an ab-initio
Br\"uckner-Hartree-Fock equation of state with the realistic Bonn-B potential
for the hadronic phase and a covariant non-local Nambu--Jona-Lasinio model for
the quark phase. We construct static hybrid star sequences and find that our
model can support stable hybrid stars with an onset of quark matter below and a maximum mass above in agreement with recent
observations. If the finite-size effects are taken into account the core is
composed of pure quark matter. Provided that the quark vector channel
interaction is small, and the finite size effects are taken into account, quark
matter appears at densities 2-3 times the nuclear saturation density. In that
case the proton fraction in the hadronic phase remains below the value required
by the onset of the direct URCA process, so that the early onset of quark
matter shall affect on the rapid cooling of the star.Comment: version to match the one published in PR
Multi-antikaonic nuclei in the relativistic mean-field theory
Properties of multi-antikaonic nuclei (MKN), where several numbers of
mesons are bound, are studied in the relativistic mean-field model, combined
with chiral dynamics for kaonic part of the thermodynamic potential. The
density profiles for nucleons and mesons, the single particle energy of
the mesons, and binding energy of the MKN are obtained. The effects of
the interactions on these quantities are discussed in
comparison with other meson (, , and )-exchange models.
It is shown that the interactions originate from two
contributions: One is the contact interaction between antikaons inherent in
chiral symmetry, and the other is the one generated through coupling between
the and meson mean fields. Both effects of the repulsive
interactions become large on the ground state properties of the MKN as the
number of the embedded mesons increases. A relation between the
multi-antikaonic nuclei and kaon condensation in infinite and uniform matter is
mentioned.Comment: 27 pages, 13 figure
Finite size effects on kaonic pasta structures
Non-uniform structures of mixed phases at the first-order phase transition to
charged kaon condensation are studied using a density functional theory within
the relativistic mean field model. Including electric field effects and
applying the Gibbs conditions in a proper way, we numerically determine density
profiles of nucleons, electrons and condensed kaons. Importance of charge
screening effects is elucidated and thereby we show that the Maxwell
construction is effectively justified. Surface effect is also studied to figure
out its effect on the density profiles
Confronting Neutron Star Cooling Theories with New Observations
With the successful launch of Chandra and XMM/Newton X-ray space missions
combined with the lower-energy band observations, we are in the position where
careful comparison of neutron star cooling theories with observations will make
it possible to distinguish among various competing theories. For instance, the
latest theoretical and observational developments already exclude both nucleon
and kaon direct URCA cooling. In this way we can now have realistic hope for
determining various important properties, such as the composition, degree of
superfluidity, the equation of state and steller radius. These developments
should help us obtain better insight into the properties of dense matter.Comment: 11 pages, 1 figur
Neutrino Opacities in Neutron Stars with Kaon Condensates
The neutrino mean free paths in hot neutron-star matter are obtained in the
presence of kaon condensates. The kaon-induced neutrino absorption process,
which is allowed only in the presence of kaon condensates, is considered for
both nondegenerate and degenerate neutrinos. The neutrino mean free path due to
this process is compared with that for the neutrino-nucleon scattering. While
the mean free path for the kaon-induced neutrino absorption process is shown to
be shorter than the ordinary two-nucleon absorption process by several orders
of magnitude when temperature is not very high, the neutrino-nucleon scattering
process has still a dominant contribution to the neutrino opacity. Thus, the
kaon-induced neutrino absorption process has a minor effect on the thermal and
dynamical evolution of protoneutron stars.Comment: 35 pages, 4 figure
Operational status of TAMA300 with the seismic attenuation system (SAS)
TAMA300 has been upgraded to improve the sensitivity at low frequencies after the last observation run in 2004. To avoid the noise caused by seismic activities, we installed a new seismic isolation system â- the TAMA seismic attenuation system (SAS). Four SAS towers for the test-mass mirrors were sequentially installed from 2005 to 2006. The recycled FabryâPerot Michelson interferometer was successfully locked with the SAS. We confirmed the reduction of both length and angular fluctuations at frequencies higher than 1 Hz owing to the SAS
Theory for the single-point velocity statistics of fully developed turbulence
We investigate the single-point velocity probability density function (PDF)
in three-dimensional fully developed homogeneous isotropic turbulence within
the framework of PDF equations focussing on deviations from Gaussianity. A
joint analytical and numerical analysis shows that these deviations may be
quantified studying correlations of dynamical quantities like pressure
gradient, external forcing and energy dissipation with the velocity. A
stationary solution for the PDF equation in terms of these quantities is
presented, and the theory is validated with the help of direct numerical
simulations indicating sub-Gaussian tails of the PDF.Comment: 6 pages, 4 figures, corrected typo in eq. (4
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