8,440 research outputs found
Quantum Hall effects of graphene with multi orbitals: Topological numbers, Boltzmann conductance and Semi-classical quantization
Hall conductance as the Chern numbers of the Berry connection
in the magnetic Brillouin zone is calculated for a realistic multi band
tight-band model of graphene with non-orthogonal basis. It is confirmed that
the envelope of coincides with a semi-classical result when
magnetic field is sufficiently small.
The Hall resistivity from the weak-field Boltzmann theory also
explains the overall behaviour of the if the Fermi surface is
composed of a single energy band. The plateaux of are explained
from semi-classical quantization and necessary modification is proposed for the
Dirac fermion regimes.Comment: 5pages, 3figure
Meta-stable Vacuum in Spontaneously Broken N=2 Supersymmetric Gauge Theory
We consider an N=2 supersymmetric SU(2) \times U(1) gauge theory with N_f=2
massless flavors and a Fayet-Iliopoulos (FI) term. In the presence of the FI
term, supersymmetry is spontaneously broken at tree level (on the Coulomb
branch), leaving a pseudo-flat direction in the classical potential. This
vacuum degeneracy is removed once quantum corrections are taken into account.
Due to the SU(2) gauge dynamics, the effective potential exhibits a local
minimum at the dyon point, where not only supersymmetry but also U(1)_R
symmetry is broken, while a supersymmetric vacuum would be realized toward
infinity with the runaway behavior of the potential. This local minimum is
found to be parametrically long-lived. Interestingly, from a phenomenological
point of view, in this meta-stable vacuum the massive hypermultiplets inherent
in the theory play the role of the messenger fields in the gauge mediation
scenario, when the Standard Model gauge group is embedded into their flavor
symmetry.Comment: 27 pages, 11 figures, journal reference added, minor modifications in
the tex
Ab initio study of the photoabsorption of He
There are some discrepancies in the low energy data on the photoabsorption
cross section of He. We calculate the cross section with realistic nuclear
forces and explicitly correlated Gaussian functions. Final state interactions
and two- and three-body decay channels are taken into account. The cross
section is evaluated in two methods: With the complex scaling method the total
absorption cross section is obtained up to the rest energy of a pion, and with
the microscopic -matrix method both cross sections He()H
and He()He are calculated below 40\,MeV. Both methods give
virtually the same result. The cross section rises sharply from the H+
threshold, reaching a giant resonance peak at 26--27\,MeV. Our calculation
reproduces almost all the data above 30\,MeV. We stress the importance of
H+ and He+ cluster configurations on the cross section as well as
the effect of the one-pion exchange potential on the photonuclear sum rule.Comment: 15 pages, 12 figure
Occupation probability of harmonic-oscillator quanta for microscopic cluster-model wave functions
We present a new and simple method of calculating the occupation probability
of the number of total harmonic-oscillator quanta for a microscopic
cluster-model wave function. Examples of applications are given to the recent
calculations including -model for He, -model for
Li, and -model for Be as well as the classical
calculations of -model for Li and -model
for C. The analysis is found to be useful for quantifying the amount of
excitations across the major shell as well as the degree of clustering. The
origin of the antistretching effect is discussed.Comment: 9 page
Non-Abelian Vortices on Cylinder -- Duality between vortices and walls
We investigate vortices on a cylinder in supersymmetric non-Abelian gauge
theory with hypermultiplets in the fundamental representation. We identify
moduli space of periodic vortices and find that a pair of wall-like objects
appears as the vortex moduli is varied. Usual domain walls also can be obtained
from the single vortex on the cylinder by introducing a twisted boundary
condition. We can understand these phenomena as a T-duality among D-brane
configurations in type II superstring theories. Using this T-duality picture,
we find a one-to-one correspondence between the moduli space of non-Abelian
vortices and that of kinky D-brane configurations for domain walls.Comment: 33 pages, 17 figures, v2: references added, typos corrected, the
final version published in PR
Miniaturization of High-Frequency Carrier-Type Thin-Film Magnetic Field Sensor Using Laminated Film
We examined a laminated high-frequency carrier-type thin-film magnetic field sensor that consists of CoNbZr soft magnetic films with Nb nonmagnetic conductive interlayer. The lamination can change domain structure of the sensor and obtain high sensitivity. An impedance change of 6 /spl Omega/ and a gain of 43 k/spl Omega//T was achieved when the length of the laminated sensor was 1 mm. The gain is four times larger than that of a monolayer sensor
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