11,267 research outputs found
A Perturbative Study of a General Class of Lattice Dirac Operators
A perturbative study of a general class of lattice Dirac operators is
reported, which is based on an algebraic realization of the Ginsparg-Wilson
relation in the form
where stands for a non-negative integer.
The choice corresponds to the commonly discussed Ginsparg-Wilson relation
and thus to the overlap operator. We study one-loop fermion contributions to
the self-energy of the gauge field, which are related to the fermion
contributions to the one-loop function and to the Weyl anomaly. We
first explicitly demonstrate that the Ward identity is satisfied by the
self-energy tensor. By performing careful analyses, we then obtain the correct
self-energy tensor free of infra-red divergences, as a general consideration of
the Weyl anomaly indicates. This demonstrates that our general operators give
correct chiral and Weyl anomalies. In general, however, the Wilsonian effective
action, which is supposed to be free of infra-red complications, is expected to
be essential in the analyses of our general class of Dirac operators for
dynamical gauge field.Comment: 30 pages. Some of the misprints were corrected. Phys. Rev. D (in
press
Influence of retardation effects on 2D magnetoplasmon spectrum
Within dissipationless limit the magnetic field dependence of magnetoplasmon
spectrum for unbounded 2DEG system found to intersect the cyclotron resonance
line, and, then approaches the frequency given by light dispersion relation.
Recent experiments done for macroscopic disc-shape 2DEG systems confirm theory
expectations.Comment: 2 pages,2 figure
Two-flavor lattice QCD simulation in the epsilon-regime with exact chiral symmetry
We perform lattice simulations of two-flavor QCD using Neuberger's overlap
fermion, with which the exact chiral symmetry is realized at finite lattice
spacings. The epsilon-regime is reached by decreasing the light quark mass down
to 3 MeV on a 16^3 32 lattice with a lattice spacing \sim 0.11 fm. We find a
good agreement of the low-lying Dirac eigenvalue spectrum with the analytical
predictions of the chiral random matrix theory, which reduces to the chiral
perturbation theory in the epsilon-regime. The chiral condensate is extracted
as \Sigma(2 GeV) = (251(7)(11) MeV)^3, where the errors are statistical and an
estimate of the higher order effects in the epsilon-expansion.Comment: 10pages, 4figure
Chiral fermions on the lattice and index relations
Comparing recent lattice results on chiral fermions and old continuum results
for the index puzzling questions arise. To clarify this issue we start with a
critical reconsideration of the results on finite lattices. We then work out
various aspects of the continuum limit. After determining bounds and norm
convergences we obtain the limit of the anomaly term. Collecting our results
the index relation of the quantized theory gets established. We then compare in
detail with the Atiyah-Singer theorem. Finally we analyze conventional
continuum approaches.Comment: 34 pages; a more detaild introduction and a subsection with remarks
on literature adde
Lorentz transformation and vector field flows
The parameter changes resulting from a combination of Lorentz transformation
are shown to form vector field flows. The exact, finite Thomas rotation angle
is determined and interpreted intuitively. Using phase portraits, the
parameters evolution can be clearly visualized. In addition to identifying the
fixed points, we obtain an analytic invariant, which correlates the evolution
of parameters.Comment: 11 pages, 3 figures. Section IV revised and title change
Contact Binary Variables as X-ray Sources
We present cross-identification of archived X-ray point sources with W UMa
variable stars found in the All-Sky Automated Survey (ASAS). In a surveyed sky
area of 300 square degrees of ASAS, 36 W UMa stars have been found associated
with X-ray emission. We compute the distances of these W UMa systems and hence
their X-ray luminosities. Our data support the "supersaturation" phenomenon
seen in these fast rotators, namely that the faster a W UMa star rotates, the
weaker its X-ray luminosity.Comment: 10 pages, 2 figures, 1 table; submitted to A
Domain wall fermion and CP symmetry breaking
We examine the CP properties of chiral gauge theory defined by a formulation
of the domain wall fermion, where the light field variables and
together with Pauli-Villars fields and are utilized. It is shown
that this domain wall representation in the infinite flavor limit is
valid only in the topologically trivial sector, and that the conflict among
lattice chiral symmetry, strict locality and CP symmetry still persists for
finite lattice spacing . The CP transformation generally sends one
representation of lattice chiral gauge theory into another representation of
lattice chiral gauge theory, resulting in the inevitable change of propagators.
A modified form of lattice CP transformation motivated by the domain wall
fermion, which keeps the chiral action in terms of the Ginsparg-Wilson fermion
invariant, is analyzed in detail; this provides an alternative way to
understand the breaking of CP symmetry at least in the topologically trivial
sector. We note that the conflict with CP symmetry could be regarded as a
topological obstruction. We also discuss the issues related to the definition
of Majorana fermions in connection with the supersymmetric Wess-Zumino model on
the lattice.Comment: 33 pages. Note added and a new reference were added. Phys. Rev.D (in
press
Hermitian quark mass matrices with four texture zeros
We provide a complete and systematic analysis of hermitian, hierarchical
quark mass matrices with four texture zeros. Using triangular mass matrices,
each pattern of texture zeros is readily shown to lead to a definite relation
between the CKM parameters and the quark masses. Nineteen pairs are found to be
consistent with present data, and one other is marginally acceptable. In
particular, no parallel structure between the up and down mass matrices is
found to be favorable with data.Comment: 18 pages, no figure, references [8] and [10] adde
Origin of the butterfly magnetoresistance in a Dirac nodal-line system
We report a study on the magnetotransport properties and on the Fermi
surfaces (FS) of the ZrSi(Se,Te) semimetals. Density Functional Theory (DFT)
calculations, in absence of spin orbit coupling (SOC), reveal that both the Se
and the Te compounds display Dirac nodal lines (DNL) close to the Fermi level
at symmorphic and non-symmorphic positions, respectively. We
find that the geometry of their FSs agrees well with DFT predictions. ZrSiSe
displays low residual resistivities, pronounced magnetoresistivity, high
carrier mobilities, and a butterfly-like angle-dependent magnetoresistivity
(AMR), although its DNL is not protected against gap opening. As in
CdAs, its transport lifetime is found to be 10 to 10 times
larger than its quantum one. ZrSiTe, which possesses a protected DNL, displays
conventional transport properties. Our evaluation indicates that both compounds
most likely are topologically trivial. Nearly angle-independent effective
masses with strong angle dependent quantum lifetimes lead to the butterfly AMR
in ZrSiSe
Magnetic moment of the pentaquark with light-cone QCD sum rules
In this article, we study the magnetic moment of the pentaquark state as diquark-diquark-antiquark () state in the
framework of the light-cone QCD sum rules approach. The numerical results
indicate the magnetic moment of the pentaquark state is about
.Comment: 10 pages, 1 figure. The main contents of this article is included in
hep-ph/0503007, this article will not be submitted to a journal for
publicatio
- …