2,766 research outputs found
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
Spectroscopy of SrRuO/Ru Junctions in Eutectic
We have investigated the tunnelling properties of the interface between
superconducting Sr2RuO4 and a single Ru inclusion in eutectic. By using a
micro-fabrication technique, we have made Sr2RuO4/Ru junctions on the eutectic
system that consists of Sr2RuO4 and Ru micro-inclusions. Such a eutectic system
exhibits surface superconductivity, called the 3-K phase. A zero bias
conductance peak (ZBCP) was observed in the 3-K phase. We propose to use the
onset of the ZBCP to delineate the phase boundary of a time-reversal symmetry
breaking state.Comment: To be published in Proc of 24th Int. Conf. on Low Temperature Physics
(LT24); 2 page
Chemical potential shift induced by double-exchange and polaronic effects in Nd_{1-x}Sr_xMnO_3
We have studied the chemical potential shift as a function of temperature in
NdSrMnO (NSMO) by measurements of core-level photoemission
spectra. For ferromagnetic samples ( and 0.45), we observed an unusually
large upward chemical potential shift with decreasing temperature in the
low-temperature region of the ferromagnetic metallic (FM) phase. This can be
explained by the double-exchange (DE) mechanism if the band is split by
dynamical/local Jahn-Teller effect. The shift was suppressed near the Curie
temperature (), which we attribute to the crossover from the DE to
lattice-polaron regimes.Comment: 5 pages, 6 figure
The dead ringer/retained transcriptional regulatory gene is required for positioning of the longitudinal glia in the Drosophila embryonic CNS
The Drosophila dead ringer (dri, also known as retained, retn) gene encodes a nuclear protein with a conserved DNA-binding domain termed the ARID (AT-rich interaction domain). We show here that dri is expressed in a subset of longitudinal glia in the Drosophila embryonic central nervous system and that dri forms part of the transcriptional regulatory cascade required for normal development of these cells. Analysis of mutant embryos revealed a role for dri in formation of the normal embryonic CNS. Longitudinal glia arise normally in dri mutant embryos, but they fail to migrate to their final destinations. Disruption of the spatial organization of the dri-expressing longitudinal glia accounts for the mild defects in axon fasciculation observed in the mutant embryos. Consistent with the late phenotypes observed, expression of the glial cells missing (gcm) and reversed polarity (repo) genes was found to be normal in dri mutant embryos. However, from stage 15 of embryogenesis, expression of locomotion defects (loco) and prospero (pros) was found to be missing in a subset of LG. This suggests that loco and pros are targets of DRI transcriptional activation in some LG. We conclude that dri is an important regulator of the late development of longitudinal glia
Self-Energy Effects on the Low- to High-Energy Electronic Structure of SrVO3
The correlated electronic structure of SrVO3 has been investigated by
angle-resolved photoemission spectroscopy using in-situ prepared thin films.
Pronounced features of band renormalization have been observed: a sharp kink
~60 meV below the Fermi level (EF) and a broad so-called "high-energy kink"
~0.3 eV below EF as in the high-Tc cuprates although SrVO3 does not show
magnetic fluctuations. We have deduced the self-energy in a wide energy range
by applying the Kramers-Kronig relation to the observed spectra. The obtained
self-energy clearly shows a large energy scale of ~0.7 eV which is attributed
to electron-electron interaction and gives rise to the ~0.3 eV "kink" in the
band dispersion as well as the incoherent peak ~1.5eV below EF. The present
analysis enables us to obtain consistent picture both for the incoherent
spectra and the band renormalization.Comment: 5 pages, 3 figure
Sigma Exchange in the Nonmesonic Decays of Light Hypernuclei and Violation of the Delta I=1/2 Rule
Nonmesonic weak decays of s-shell hypernuclei are analyzed in microscopic
models for the Lambda N to NN weak interaction. A scalar-isoscalar meson,
sigma, is introduced and its importance in accounting the decay rates, n/p
ratios and proton asymmetry is demonstrated. Possible violation of the Delta
I=1/2 rule in the nonmesonic weak decay of Lambda is discussed in a
phenomenological analysis and several useful constraints are presented. The
microscopic calculation shows that the current experimental data indicate a
large violation of the Delta I=1/2 rule, although no definite conclusion can be
derived due to large ambiguity of the decay rate of {^4_Lambda H}.Comment: 13 pages, 5 figure
Spectroscopy and Imaging Performance of the Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT)
LXeGRIT is a balloon-borne Compton telescope based on a liquid xenon time
projection chamber (LXeTPC) for imaging cosmic \g-rays in the energy band of
0.2-20 MeV. The detector, with 400 cm area and 7 cm drift gap, is filled
with high purity LXe. Both ionization and scintillation light signals are
detected to measure the energy deposits and the three spatial coordinates of
individual \g -ray interactions within the sensitive volume. The TPC has been
characterized with repeated measurements of its spectral and Compton imaging
response to \g -rays from radioactive sources such as \na, \cs, \yt and Am-Be.
The detector shows a linear response to \g -rays in the energy range 511 keV
-4.4 MeV, with an energy resolution (FWHM) of \Delta E/E=8.8% \: \sqrt{1\MeV
/E}. Compton imaging of \yt \g -ray events with two detected interactions is
consistent with an angular resolution of 3 degrees (RMS) at 1.8 MeV.Comment: To appear in: Hard X-Ray, Gamma-Ray and Neutron Detector Physics XI,
2000; Proc. SPIE, vol. 4140; K.A. Flanagan & O.H. Siegmund, ed
- …