12,181 research outputs found

### A Numerical Study of Spectral Flows of Hermitian Wilson-Dirac Operator and the Index Theorem in Abelian Gauge Theories on Finite Lattices

We investigate the index of the Neuberger's Dirac operator in abelian gauge
theories on finite lattices by numerically analyzing the spectrum of the
hermitian Wilson-Dirac operator for a continuous family of gauge fields
connecting different topological sectors. By clarifying the characteristic
structure of the spectrum leading to the index theorem we show that the index
coincides to the topological charge for a wide class of gauge field
configurations. We also argue that the index can be found exactly for some
special but nontrivial configurations in two dimensions by directly analyzing
the spectrum.Comment: 13 pages, 3 figures, minor modifications including typos, a reference
adde

### Fermi surfaces and anomalous transport in quasicrystals

Fermi surfaces of several quasicrystalline approximants are calculated by
means of ab-initio methods which enable direct comparison with dHvA
experiments. A criterion for anomalous metallic transport is proposed and
power-law temperature dependence of electronic conductivity is deduced from
scaling analysis of the Kubo formula.Comment: 8 pages, 7 figures. to appear in Phys. Rev.

### Spectrum of the Hermitian Wilson-Dirac Operator for a Uniform Magnetic Field in Two Dimensions

It is shown that the eigenvalue problem for the hermitian Wilson-Dirac
operator of for a uniform magnetic field in two dimensions can be reduced to
one-dimensional problem described by a relativistic analog of the Harper
equation. An explicit formula for the secular equations is given in term of a
set of polynomials. The spectrum exhibits a fractal structure in the infinite
volume limit. An exact result concerning the index theorem for the overlap
Dirac operator is obtained.Comment: 8 pages, latex, 3 eps figures, minor correction

### Single-Particle Spin-Orbit Strengths of the Nucleon and Hyperons by SU6 Quark-Model

The quark-model hyperon-nucleon interaction suggests an important
antisymmetric spin-orbit component. It is generated from a color analogue of
the Fermi-Breit interaction dominating in the one-gluon exchange process
between quarks. We discuss the strength S_B of the single-particle spin-orbit
potential, following the Scheerbaum's prescription. Using the SU6 quark-model
baryon-baryon interaction which was recently developed by the Kyoto-Niigata
group, we calculate NN, Lambda N and Sigma N G-matrices in symmetric nuclear
matter and apply them to estimate the strength S_B. The ratio of S_B to the
nucleon strength S_N =~ -40 MeV*fm^5 is (S_Lambda)/(S_N) =~ 1/5 and
(S_Sigma)/(S_N) =~ 1/2 in the Born approximation. The G-matrix calculation of
the model FSS modifies S_Lambda to (S_Lambda)/(S_N) =~ 1/12. For S_N and
S_Sigma, the effect of the short-range correlation is comparatively weak
against meson-exchange potentials with a short-range repulsive core. The
significant reduction of the Lambda single-particle potential arises from the
combined effect of the antisymmetric LS force, the flavor-symmetry breaking
originating from the strange to up-down quark-mass difference, as well as the
effect of the short-range correlation. The density dependence of S_B is also
examined.Comment: 26 page

### Topological Charge of Lattice Abelian Gauge Theory

Configuration space of abelian gauge theory on a periodic lattice becomes
topologically disconnected by excising exceptional gauge field configurations.
It is possible to define a U(1) bundle from the nonexceptional link variables
by a smooth interpolation of the transition functions. The lattice analogue of
Chern character obtained by a cohomological technique based on the
noncommutative differential calculus is shown to give a topological charge
related to the topological winding number of the U(1) bundle.Comment: 20 pages, latex, nofigur

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