3,467 research outputs found
Interaction of massless Dirac field with a Poincar\'e gauge field
In this paper we consider a model of Poincar\'e gauge theory (PGT) in which a
translational gauge field and a Lorentz gauge field are actually identified
with the Einstein's gravitational field and a pair of ``Yang-Mills'' field and
its partner, respectively.In this model we re-derive some special solutions and
take up one of them. The solution represents a ``Yang-Mills'' field without its
partner field and the Reissner-Nordstr\"om type spacetime, which are generated
by a PGT-gauge charge and its mass.It is main purpose of this paper to
investigate the interaction of massless Dirac fields with those fields. As a
result, we find an interesting fact that the left-handed massless Dirac fields
behave in the different manner from the right-handed ones. This can be
explained as to be caused by the direct interaction of Dirac fields with the
``Yang-Mills'' field. Accordingly, the phenomenon can not happen in the
behavior of the neutrino waves in ordinary Reissner-Nordstr\"om geometry. The
difference between left- and right-handed effects is calculated quantitatively,
considering the scattering problems of the massless Dirac fields by our
Reissner-Nordstr\"om type black-hole.Comment: 10pages, RevTeX3.
Two-pion bound state in sigma channel at finite temperature
We study how we can understand the change of the spectral function and the
pole location of the correlation function for sigma at finite temperature,
which were previously obtained in the linear sigma model with a resummation
technique called optimized perturbation theory. There are two relevant poles in
the sigma channel. One pole is the original sigma pole which shows up as a
broad peak at zero temperature and becomes lighter as the temperature
increases. The behavior is understood from the decreasing of the sigma
condensate, which is consistent with the Brown-Rho scaling. The other pole
changes from a virtual state to a bound state of pion-pion as the temperature
increases which causes the enhancement at the pion-pion threshold. The behavior
is understood as the emergence of the pion-pion bound state due to the
enhancement of the pion-pion attraction by the induced emission in medium. The
latter pole, not the former, eventually degenerates with pion above the
critical temperature of the chiral transition. This means that the observable
"sigma" changes from the former to the latter pole, which can be interpreted as
the level crossing of "sigma" and pion-pion at finite temperature.Comment: 4 pages, 4 figure
Canonical Quantization of SU(3) Skyrme Model in a General Representation
A complete canonical quantization of the SU(3) Skyrme model performed in the
collective coordinate formalism in general irreducible representations. In the
case of SU(3) the model differs qualitatively in different representations. The
Wess-Zumino-Witten term vanishes in all self-adjoint representations in the
collective coordinate method for separation of space and time variables. The
canonical quantization generates representation dependent quantum mass
corrections, which can stabilize the soliton solution. The standard symmetry
breaking mass term, which in general leads to representation mixing,
degenerates to the SU(2) form in all self-adjoint representations.Comment: 24 RevTex4 pages, no figure
High Throughput Oxide Lattice Engineering by Parallel Laser Molecular Beam Epitaxy and Concurrent X-ray Diffraction
A novel laser molecular beam epitaxy (LMBE) system for the fabrication of
atomically controlled oxides superlattices and an x-ray diffractometer that
measures spatially-resolved x-ray diffraction spectra have been developed based
on the concept of combinatorial methodology. The LMBE chamber has two moving
masks, an automated target stage, a substrate heating laser, and an in-situ
scanning reflection high-energy electron diffraction system. The x-ray
diffractometer with a curved monochromator and two-dimensional detector is used
for rapid concurrent x-ray diffraction intensity mapping with the two axes of
the detector corresponding to the diffraction angle and a position in the
sample.Comment: 19pages, 9figure
AMPTE/CCE‐SCATHA simultaneous observations of substorm‐associated magnetic fluctuations
This study examines substorm-associated magnetic field fluctuations observed by the AMPTE/CCE and SCATHA satellites in the near-Earth tail. Three tail reconfiguration events are selected, one event on August 28, 1986, and two consecutive events on August 30, 1986. The fractal analysis was applied to magnetic field measurements of each satellite. The result indicates that (1) the amplitude of the fluctuation of the north-south magnetic component is larger, though not overwhelmingly, than the amplitudes of the other two components and (2) the magnetic fluctuations do have a characteristic timescale, which is several times the proton gyroperiod. In the examined events the satellite separation was less than 10 times the proton gyroradius. Nevertheless, the comparison between the AMPTE/CCE and SCATHA observations indicates that (3) there was a noticeable time delay between the onsets of the magnetic fluctuations at the two satellite positions, which is too long to ascribe to the propagation of a fast magnetosonic wave, and (4) the coherence of the magnetic fluctuations was low in the August 28, 1986, event and the fluctuations had different characteristic timescales in the first event of August 30, 1986, whereas some similarities can be found for the second event of August 30, 1986. Result 1 indicates that perturbation electric currents associated with the magnetic fluctuations tend to flow parallel to the tail current sheet and are presumably related to the reduction of the tail current intensity. Results 2 and 3 suggest that the excitation of the magnetic fluctuations and therefore the trigger of the tail current disruption is a kinetic process in which ions play an important role. It is inferred from results 3 and 4 that the characteristic spatial scale of the associated instability is of the order of the proton gyroradius or even shorter, and therefore the tail current disruption is described as a system of chaotic filamentary electric currents. However, result 4 suggests that the nature of the tail current disruption can vary from event to event
Electronic Structure of the Chevrel-Phase Compounds SnMoSe: Photoemission Spectroscopy and Band-structure Calculations
We have studied the electronic structure of two Chevrel-phase compounds,
MoSe and SnMoSe, by combining photoemission
spectroscopy and band-structure calculations. Core-level spectra taken with
x-ray photoemission spectroscopy show systematic core-level shifts, which do
not obey a simple rigid-band model. The inverse photoemission spectra imply the
existence of an energy gap located eV above the Fermi level, which is
a characteristic feature of the electronic structure of the Chevrel compounds.
Quantitative comparison between the photoemission spectra and the
band-structure calculations have been made. While good agreement between theory
and experiment in the wide energy range was obtained as already reported in
previous studies, we found that the high density of states near the Fermi level
predicted theoretically due to the Van Hove singularity is considerably reduced
in the experimental spectra taken with higher energy resolution than in the
previous reports. Possible origins are proposed to explain this observation.Comment: 8 pages, 5 figure
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