17,164 research outputs found
Transverse Ward-Takahashi Identity, Anomaly and Schwinger-Dyson Equation
Based on the path integral formalism, we rederive and extend the transverse
Ward-Takahashi identities (which were first derived by Yasushi Takahashi) for
the vector and the axial vector currents and simultaneously discuss the
possible anomaly for them. Subsequently, we propose a new scheme for writing
down and solving the Schwinger-Dyson equation in which the the transverse
Ward-Takahashi identity together with the usual (longitudinal) Ward-Takahashi
identity are applied to specify the fermion-boson vertex function. Especially,
in two dimensional Abelian gauge theory, we show that this scheme leads to the
exact and closed Schwinger-Dyson equation for the fermion propagator in the
chiral limit (when the bare fermion mass is zero) and that the Schwinger-Dyson
equation can be exactly solved.Comment: 22 pages, latex, no figure
Future of Ultraviolet Astronomy Based on Six Years of IUE Research
Physical insights into the various astronomical objects which were studied using the International Ultraviolet Explorer (IUE) satellite. Topics covered included galaxies, cool stars, hot stars, close binaries, variable stars, the interstellar medium, the solar system, and IUE follow-on missions
Spontaneous Chiral-Symmetry Breaking in Three-Dimensional QED with a Chern--Simons Term
In three-dimensional QED with a Chern--Simons term we study the phase
structure associated with chiral-symmetry breaking in the framework of the
Schwinger--Dyson equation. We give detailed analyses on the analytical and
numerical solutions for the Schwinger--Dyson equation of the fermion
propagator, where the nonlocal gauge-fixing procedure is adopted to avoid
wave-function renormalization for the fermion. In the absence of the
Chern--Simons term, there exists a finite critical number of four-component
fermion flavors, at which a continuous (infinite-order) chiral phase transition
takes place and below which the chiral symmetry is spontaneously broken. In the
presence of the Chern--Simons term, we find that the spontaneous
chiral-symmetry-breaking transition continues to exist, but the type of phase
transition turns into a discontinuous first-order transition. A simple
stability argument is given based on the effective potential, whose stationary
point gives the solution of the Schwinger-Dyson equation.Comment: 34 pages, revtex, with 9 postscriptfigures appended (uuencoded
Loewner driving functions for off-critical percolation clusters
We numerically study the Loewner driving function U_t of a site percolation
cluster boundary on the triangular lattice for p<p_c. It is found that U_t
shows a drifted random walk with a finite crossover time. Within this crossover
time, the averaged driving function shows a scaling behavior -(p_c-p)
t^{(\nu +1)/2\nu} with a superdiffusive fluctuation whereas, beyond the
crossover time, the driving function U_t undergoes a normal diffusion with
Hurst exponent 1/2 but with the drift velocity proportional to (p_c-p)^\nu,
where \nu= 4/3 is the critical exponent for two-dimensional percolation
correlation length. The crossover time diverges as (p_c-p)^{-2\nu} as p\to p_c.Comment: 4 pages, 7 figure
On ghost condensation, mass generation and Abelian dominance in the Maximal Abelian Gauge
Recent work claimed that the off-diagonal gluons (and ghosts) in pure
Yang-Mills theories, with Maximal Abelian gauge fixing (MAG), attain a
dynamical mass through an off-diagonal ghost condensate. This condensation
takes place due to a quartic ghost interaction, unavoidably present in MAG for
renormalizability purposes. The off-diagonal mass can be seen as evidence for
Abelian dominance. We discuss why ghost condensation of the type discussed in
those works cannot be the reason for the off-diagonal mass and Abelian
dominance, since it results in a tachyonic mass. We also point out what the
full mechanism behind the generation of a real mass might look like.Comment: 7 pages; uses revtex
Self-interaction effects on screening in three-dimensional QED
We have shown that self interaction effects in massive quantum
electrodynamics can lead to the formation of bound states of quark antiquark
pairs. A current-current fermion coupling term is introduced, which induces a
well in the potential energy profile. Explicit expressions of the effective
potential and renormalized parameters are provided
Scattered light in the IUE spectra of Epsilon Aurigae
As a result of this work it was found that light scattered from the longer wavelengths constitutes a small but non-negligible, wavelength and time dependent fraction of the measured flux in the far UV. The reality of the UV excess has not been unambigiously ruled out. However, it is noted that there are still uncertainties in the assumed scattering profile. New measurements of the scattering properties of the cross disperser grating are planned in order to verify the results of Mount and Fastie and extend the wavelength coverage into the far wings of the profile. The results of these measurements will no doubt reduce some of these uncertainties. For the present, it is felt that the BCH approach is a significant improvement over the methods heretofore available for the treatment of scattered light in IUE spectra
KUV 01584-0939: A Helium-transferring Cataclysmic Variable with an Orbital Period of 10 Minutes
High speed photometry of KUV 01584-0939 (alias Cet3) shows that is has a
period of 620.26 s. Combined with its hydrogen-deficient spectrum, this implies
that it is an AM CVn star. The optical modulation is probably a superhump, in
which case the orbital period will be slightly shorter than what we have
observed.Comment: Published by PASP. See also the latest Early-Release Research Paper
website of the PAS
The Alternating Groups and K3 Surfaces
In this note, we consider all possible extensions G of a non-trivial perfect
group H acting faithfully on a K3 surface X. The pair (X, G) is proved to be
uniquely determined by G if the transcendental value of G is maximum. In
particular, we have G/H < Z/(2) + Z/(2), if H is the alternating group A_5 and
normal in G.Comment: Journal of Pure and Applied Algebra (21 pages) to appea
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