3,205 research outputs found
Decay in the Nambu-Jona-Lasinio Model
We study the decays using the version of
the Nambu-Jona-Lasinio model with the effective nonleptonic weak
interaction. The amplitude is in reasonable agreement with
experimental data. On the other hand, the calculated
amplitudes strongly depend on the mass of the low-lying scalar-isoscalar
meson, and therefore give a strong constraint on the parameters of the
model.Comment: 10 pages, 3 Postscript figures, Talk given at YITP Workshp: From
Hadronic Matter to Quark Matter: Evolving View of Hadronic Matter, Kyoto,
Japan, Oct. 30-Nov. 1, 1994, to be published in Prog. Theor. Phys. Supp
-Meson Decays and Strong Breaking in the Three-Flavor Nambu-Jona-Lasinio Model
We study the and
decays using an extended three-flavor Nambu-Jona-Lasinio model that includes
the 't~Hooft instanton induced interaction. We find that the -meson mass,
the decay width and the
decay width are in good agreement with the experimental values when the
breaking is strong and the flavor singlet-octet mixing angle
is about zero. The effects of the breaking on the baryon
number one and two systems are also studied.Comment: 12 pages, LaTeX, 2 eps figures, Talk given at the Joint
Japan-Australia Workshop on Quarks, Hadrons and Nuclei, Adelaide, Australia,
Nov. 15-24, 199
Topological susceptibility at zero and finite temperature in the Nambu-Jona-Lasinio model
We consider the three flavor Nambu-Jona-Lasinio model with the 't Hooft
interaction incorporating the U(1)_A anomaly. In order to set the coupling
strength of the 't Hooft term, we employ the topological susceptibility
instead of the eta' meson mass. The value for is taken from lattice
simulations. We also calculate at finite temperature within the model.
Comparing it with the lattice data, we extract information about the behavior
of the U(1)_A anomaly at finite temperature. We conclude that within the
present framework, the effective restoration of the U(1)_A symmetry does not
necessarily take place even at high temperature where the chiral symmetry is
restored.Comment: 9 pages, 14 figures, to be published in Phys.Rev.
N-body + Magnetohydrodynamical Simulations of Merging Clusters of Galaxies: Characteristic Magnetic Field Structures Generated by Bulk Flow Motion
We present results from N-body + magnetohydrodynamical simulations of merging
clusters of galaxies. We find that cluster mergers cause various characteristic
magnetic field structures because of the strong bulk flows in the intracluster
medium. The moving substructures result in cool regions surrounded by the
magnetic field. These will be recognized as magnetized cold fronts in the
observational point of view. A relatively ordered magnetic field structure is
generated just behind the moving substructure. Eddy-like field configurations
are also formed by Kelvin-Helmholtz instabilities. These features are similarly
seen even in off-center mergers though the detailed structures change slightly.
The above-mentioned characteristic magnetic field structures are partly
recognized in Faraday rotation measure maps. The higher absolute values of the
rotation measure are expected when observed along the collision axis, because
of the elongated density distribution and relatively ordered field structure
along the axis. The rotation measure maps on the cosmic microwave background
radiation, which covers clusters entirely, could be useful probes of not only
the magnetic field structures but also the internal dynamics of the
intracluster medium.Comment: Accepted for publication in Ap
Chemical potential jump between hole- and electron-doped sides of ambipolar high-Tc cuprate
In order to study an intrinsic chemical potential jump between the hole- and
electron-doped high-Tc superconductors, we have performed core-level X-ray
photoemission spectroscopy (XPS) measurements of Y0.38La0.62Ba1.74La0.26Cu3Oy
(YLBLCO), into which one can dope both holes and electrons with maintaining the
same crystal structure. Unlike the case between the hole-doped system
La_2-xSrxCuO4 and the electron-doped system Nd_2-xCexCuO4, we have estimated
the true chemical potential jump between the hole- and electron-doped YLBLCO to
be ~0.8 eV, which is much smaller than the optical gaps of 1.4-1.7 eV reported
for the parent insulating compounds. We attribute the reduced jump to the
indirect nature of the charge-excitation gap as well as to the polaronic nature
of the doped carriers.Comment: 4 pages, 3 figure
Electronic charges and electric potential at LaAlO3/SrTiO3 interfaces studied by core-level photoemission spectroscopy
We studied LaAlO3/SrTiO3 interfaces for varying LaAlO3 thickness by
core-level photoemission spectroscopy. In Ti 2p spectra for conducting "n-type"
interfaces, Ti3+ signals appeared, which were absent for insulating "p-type"
interfaces. The Ti3+ signals increased with LaAlO3 thickness, but started well
below the critical thickness of 4 unit cells for metallic transport. Core-level
shifts with LaAlO3 thickness were much smaller than predicted by the polar
catastrophe model. We attribute these observations to surface
defects/adsorbates providing charges to the interface even below the critical
thickness
Turbulence Generation by Substructure Motion in Clusters of Galaxies
Clusters of galaxies form through major merger and/or absorption of smaller
groups. In fact, some characteristic structures such as cold fronts, which are
likely relevant to moving substructures, are found by {\it Chandra}. It is
expected that moving substructures generate turbulence in the intracluster
medium (ICM). Such turbulence probably plays a crucial role in mixture and
transport of gas energy and heavy elements, and particle acceleration. The {\it
Astro-E2} satellite, which is planned to be launched in 2005, will detect
broadened lines due to turbulent motion. In order to explore the
above-mentioned issues, it is important to investigate the generation processes
and structure of ICM turbulence. We investigate the ICM dynamical evolution in
and around a moving substructure with three-dimensional hydrodynamical
simulations. Eddy-like structures develop near the boundary between the
substructure and the ambient ICM through Kelvin-Helmholtz instabilities.
Because of these structures, characteristic patterns appear in the
line-of-sight velocity distribution of the ICM.Comment: 6 pages, 3 figures, Accepted for publication in Advances in Space
Research (Proceedings of COSPAR-2004
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