11,890 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
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
Effective mass theory of monolayer \delta-doping in the high-density limit
Monolayer \delta-doped structures in silicon have attracted renewed interest
with their recent incorporation into atomic-scale device fabrication strategies
as source and drain electrodes and in-plane gates. Modeling the physics of
\delta-doping at this scale proves challenging, however, due to the large
computational overhead associated with ab initio and atomistic methods. Here,
we develop an analytical theory based on an effective mass approximation. We
specifically consider the Si:P materials system, and the limit of high donor
density, which has been the subject of recent experiments. In this case,
metallic behavior including screening tends to smooth out the local disorder
potential associated with random dopant placement. While smooth potentials may
be difficult to incorporate into microscopic, single-electron analyses, the
problem is easily treated in the effective mass theory by means of a jellium
approximation for the ionic charge. We then go beyond the analytic model,
incorporating exchange and correlation effects within a simple numerical model.
We argue that such an approach is appropriate for describing realistic,
high-density, highly disordered devices, providing results comparable to
density functional theory, but with greater intuitive appeal, and lower
computational effort. We investigate valley coupling in these structures,
finding that valley splitting in the low-lying \Gamma band grows much more
quickly than the \Gamma-\Delta band splitting at high densities. We also find
that many-body exchange and correlation corrections affect the valley splitting
more strongly than they affect the band splitting
COMPARISON OF KNEE JOINT MONENTS DURING ANTICIPATED AND UNANTICIPATED RUNNING AND CUTTING MANEUVER - A PILOT STUDY
INTRODUCTION: Knee joint injuries are common in sports activities. Because it is understood that non-contact ACL injuries most often occur during cutting or landing tasks, biomechanical studies have examined in lower extremity kinematics. Cutting maneuvers during sporting are not always anticipated, and usually occur as a sudden reaction to an external stimulus. Therefore, the purpose of this study was to compare the joint moments in the lower extremity of females during anticipated and unanticipated running and cutting manoeuvres
Analysis of cubic permutation polynomials for turbo codes
Quadratic permutation polynomials (QPPs) have been widely studied and used as
interleavers in turbo codes. However, less attention has been given to cubic
permutation polynomials (CPPs). This paper proves a theorem which states
sufficient and necessary conditions for a cubic permutation polynomial to be a
null permutation polynomial. The result is used to reduce the search complexity
of CPP interleavers for short lengths (multiples of 8, between 40 and 352), by
improving the distance spectrum over the set of polynomials with the largest
spreading factor. The comparison with QPP interleavers is made in terms of
search complexity and upper bounds of the bit error rate (BER) and frame error
rate (FER) for AWGN and for independent fading Rayleigh channels. Cubic
permutation polynomials leading to better performance than quadratic
permutation polynomials are found for some lengths.Comment: accepted for publication to Wireless Personal Communications (19
pages, 4 figures, 5 tables). The final publication is available at
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Measurement of the Base Noise of Hermetic Compressor and Its Application to the Design of Muffler System and Compressor Shell
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