2,196 research outputs found
Gravitational Lorentz anomaly from the overlap formula in 2-dimensions
In this letter we show that the overlap formulation of chiral gauge theories
correctly reproduces the gravitational Lorentz anomaly in 2-dimensions. This
formulation has been recently suggested as a solution to the fermion doubling
problem on the lattice. The well known response to general coordinate
transformations of the effective action of Weyl fermions coupled to gravity in
2-dimensions can also be recovered.Comment: 7 pages, late
On Dirac Zero Modes in Hyperdiamond Model
Using the SU(5) symmetry of the 4D hyperdiamond and results on the study of
4D graphene given in "Four Dimensional Graphene" (L.B Drissi, E.H Saidi, M.
Bousmina, CPM-11-01, Phys. Rev. D (2011)), we engineer a class of 4D lattice
QCD fermions whose Dirac operators have two zero modes. We show that generally
the zero modes of the Dirac operator in hyperdiamond fermions are captured by a
tensor {\Omega}_{{\mu}}^{l} with 4\times5 complex components linking the
Euclidean SO(4) vector {\mu}; and the 5-dimensional representation of SU(5).
The Bori\c{c}i-Creutz (BC) and the Karsten-Wilzeck (KW) models as well as their
Dirac zero modes are rederived as particular realizations of
{\Omega}_{{\mu}}^{l}. Other features are also given. Keywords: Lattice QCD,
Bori\c{c}i-Creutz and Karsten-Wilzeck models, 4D hyperdiamond, 4D graphene,
SU(5) Symmetry.Comment: LaTex, 28 pages, To appear in Phys Rev
Nonlocal lattice fermion models on the 2d torus
Abelian fermion models described by the SLAC action are considered on a
finite 2d lattice. It is shown that modification of these models by introducing
additional Pauli - Villars regularization supresses nonlocal effects and
provides agreement with the continuum results in vectorial U(1) models. In the
case of chiral fermions the phase of the determinant differs from the continuum
one.Comment: 16 pages, LaTeX, 5 eps figures, uses epsf.sty, rotate.st
Constraints on the Existence of Chiral Fermions in Interacting Lattice Theories
It is shown that an interacting theory, defined on a regular lattice, must
have a vector-like spectrum if the following conditions are satisfied:
(a)~locality, (b)~relativistic continuum limit without massless bosons, and
(c)~pole-free effective vertex functions for conserved currents.
The proof exploits the zero frequency inverse retarded propagator of an
appropriate set of interpolating fields as an effective quadratic hamiltonian,
to which the Nielsen-Ninomiya theorem is applied.Comment: LaTeX, 9 pages, WIS--93/56--JUNE--P
Hamiltonian domain wall fermions at strong coupling
We apply strong-coupling perturbation theory to gauge theories containing
domain-wall fermions in Shamir's surface version. We construct the effective
Hamiltonian for the color-singlet degrees of freedom that constitute the
low-lying spectrum at strong coupling. We show that the effective theory is
identical to that derived from naive, doubled fermions with a mass term, and
hence that domain-wall fermions at strong coupling suffer both doubling and
explicit breaking of chiral symmetry. Since we employ a continuous fifth
dimension whose extent tends to infinity, our result applies to overlap
fermions as well.Comment: Revtex, 21 pp. Some changes in Introduction, dealing with consistency
with previous wor
Manifestly Gauge Covariant Treatment of Lattice Chiral Fermion
We propose a lattice formulation of the chiral fermion which maximally
respects the gauge symmetry and simultaneously is free of the unwanted species
doublers. The formulation is based on the lattice fermion propagator and
composite operators, rather than on the lattice fermion action. The fermionic
determinant is defined as a functional integral of an expectation value of the
gauge current operator with respect to the background gauge field: The gauge
anomaly is characterized as the non-integrability. We perform some perturbative
test to confirm the gauge covariance and an absence of the doublers. The
formulation can be applied rather straightforwardly to numerical simulations in
the quenched approximation.Comment: 11 pages, phyzzx, The final version to appear in Phys. Rev.
Josephson current through a molecular transistor in a dissipative environment
We study the Josephson coupling between two superconductors through a single
correlated molecular level, including Coulomb interaction on the level and
coupling to a bosonic environment. All calculations are done to the lowest,
i.e., the fourth, order in the tunneling coupling and we find a suppression of
the supercurrent due to the combined effect of the Coulomb interaction and the
coupling to environmental degrees of freedom. Both analytic and numerical
results are presented.Comment: 11 pages, 6 figures, to appear in Phys. Rev. B; v3: several misprints
corrected - in particular, sign inconsistencies throughout the paper should
be fixe
Remark on Pauli-Villars Lagrangian on the Lattice
It is interesting to superimpose the Pauli-Villars regularization on the
lattice regularization. We illustrate how this scheme works by evaluating the
axial anomaly in a simple lattice fermion model, the Pauli-Villars Lagrangian
with a gauge non-invariant Wilson term. The gauge non-invariance of the axial
anomaly, caused by the Wilson term, is remedied by a compensation among
Pauli-Villars regulators in the continuum limit. A subtlety in Frolov-Slavnov's
scheme for an odd number of chiral fermions in an anomaly free complex gauge
representation, which requires an infinite number of regulators, is briefly
mentioned.Comment: 14 pages, Phyzzx. The final version to appear in Phys. Rev.
Phylogeny of Holocacista capensis (Lepidoptera: Heliozelidae) from Vineyards and Natural Forests in South Africa Inferred from Mitochondrial and Nuclear Genes
In South Africa, the family Heliozelidae in the order Lepidoptera is restricted to four known species. The grapevine leaf miner, Holocacista capensis, feeds between the epidermal layers of a grapevine leaf,predominantly along the leaf margin. A final instar larva will descend from the blotch mine/gallery to attach its cocoon casing (constructed from the epidermal layers of the mined gallery) to any object belowthe infested leaf. Five monophyletic clades and a polyphyletic group have been identified within the Heliozelidae, using a mitochondrially encoded gene cytochrome c oxidase I (COI) and a nuclear gene,histone 3 (H3). An exploratory study of the genetic diversity within H. capensis populations was conducted using these genes. The phylogenetic analyses of COI indicate that H. capensis that are currently beingcollected from South Africa fall within three clades/haplotypes, of which one is well supported and contains only one species from Gauteng, and one has three specimens from two different areas in the Western Capeprovince, while 80% belong to haplotype 1 (H1). The current study can be used as a starting point for future DNA-based studies aimed at gaining insight into possible patterns of diversity in H. capensis toconfirm switching from native to commercial grapevine hosts. However, more samples need to be collected from different areas in South Africa
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