2,209 research outputs found
Dual Interpretations of Pion Clouds at RHIC
A gauge theory of pions interacting with rho-mesons at elevated temperatures
is used to calculate the pressure in a hot pion gas. No reference is made to
the pion's status as a QCD Goldstone boson. The role of the pion is merely that
of a carrier of an SU(2) symmetry, gauged to create a vector-meson interaction,
the rho playing the role of the interacting vector particle. The results are in
rough agreement with much more elaborate calculations, both of the purely
hadronic variety, and those that invoke quark-gluon degrees of freedom. The
quark-gluon and purely hadronic calculations seemingly lead to very similar
predictions which are in accord with receent data from RHIC. The results
motivate the question as to whether the two descriptions are dual to each other
in the sense of being alternate models, each sufficient to explain the observed
data.Comment: 11 pages, 4 figures (2 eps files, 1 ps file) + a figure that uses
metafont package feynmf, also forwarded. Open with "latex feynmf.ins". See
http://www.ctan.org/tex-archive/help/Catalogue/entries/feynmf.html 9/6/06
replaced figure 2 with scaled version of sam
Mass singularity and confining property in
We discuss the properties of the position space fermion propagator in three
dimensional QED which has been found previouly based on Ward-Takahashi-identity
for soft-photon emission vertex and spectral representation.There is a new type
of mass singularity which governs the long distance behaviour.It leads the
propagator vanish at large distance.This term corresponds to dynamical mass in
position space.Our model shows confining property and dynamical mass generation
for arbitrary coupling constant.Since we used dispersion retation in deriving
spectral function there is a physical mass which sets a mass scale.For finite
cut off we obtain the full propagator in the dispersion integral as a
superposition of different massses.Low energy behaviour of the proagator is
modified to decrease by position dependent mass.In the limit of zero infrared
cut-off the propagator vanishes with a new kind of infrared behaviour.Comment: 22pages,4figures,revtex4,Notational sloppiness are crrected.Submitted
to JHE
A new look at the problem of gauge invariance in quantum field theory
Quantum field theory is assumed to be gauge invariant. However it is well
known that when certain quantities are calculated using perturbation theory the
results are not gauge invariant. The non-gauge invariant terms have to be
removed in order to obtain a physically correct result. In this paper we will
examine this problem and determine why a theory that is supposed to be gauge
invariant produces non-gauge invariant results.Comment: Accepted by Physica Scripta. 27 page
Pt-incorporated anatase TiO2(001) surface for solar cell applications : First-principles density functional theory calculations
First-principles density functional theory calculations were carried out to
determine the low energy geometries of anatase TiO(001) with Pt implants in
the sublayers as substitutional and interstitial impurities as well as on the
surface in the form of adsorbates. We investigated the effect of such a
systematic Pt incorporation in the electronic structure of this surface for
isolated and interacting impurities with an emphasis on the reduction in the
band gap to visible region. Comprehensive calculations, for 1x1 surface, showed
that Pt ions at interstitial cavities result in local segregation, forming
metallic wires inside, while substitution for bulk Ti and adsorption drives
four strongly dispersed impurity states from valence-bands up in the gap with a
narrowing of ~1.5 eV. Hence, such a contiguous Pt incorporation drives anatase
into infrared regime. Pt substitution for the surface Ti, on the other hand,
metallizes the surface. Systematic trends for 2x2 surface revealed that Pt can
be encapsulated inside to form stable structures as a result of strong Pt-O
interactions as well as the adsorptional and substitutional cases. Dilute
impurities considered for 2x2 surface models exhibit flat-like defect states
driven from the valence bands narrowing the energy gap suitable to obtain
visible light responsive titania.Comment: 15 pages, 8 figures, 4 tables. to appear on Phys. Rev
Abelian 2-form gauge theory: special features
It is shown that the four -dimensional (4D) free Abelian 2-form
gauge theory provides an example of (i) a class of field theoretical models for
the Hodge theory, and (ii) a possible candidate for the quasi-topological field
theory (q-TFT). Despite many striking similarities with some of the key
topological features of the two -dimensional (2D) free Abelian (and
self-interacting non-Abelian) gauge theories, it turns out that the 4D free
Abelian 2-form gauge theory is {\it not} an exact TFT. To corroborate this
conclusion, some of the key issues are discussed. In particular, it is shown
that the (anti-)BRST and (anti-)co-BRST invariant quantities of the 4D 2-form
Abelian gauge theory obey the recursion relations that are reminiscent of the
exact TFTs but the Lagrangian density of this theory is not found to be able to
be expressed as the sum of (anti-)BRST and (anti-)co-BRST exact quantities as
is the case with the {\it topological} 2D free Abelian (and self-interacting
non-Abelian) gauge theories.Comment: LaTeX, 23 pages, journal ref. give
Superfield Approach to (Non-)local Symmetries for One-Form Abelian Gauge Theory
We exploit the geometrical superfield formalism to derive the local,
covariant and continuous Becchi-Rouet-Stora-Tyutin (BRST) symmetry
transformations and the non-local, non-covariant and continuous dual-BRST
symmetry transformations for the free Abelian one-form gauge theory in four -dimensions (4D) of spacetime. Our discussion is carried out in the
framework of BRST invariant Lagrangian density for the above 4D theory in the
Feynman gauge. The geometrical origin and interpretation for the (dual-)BRST
charges (and the transformations they generate) are provided in the language of
translations of some superfields along the Grassmannian directions of the six
(-dimensional supermanifold parametrized by the four spacetime and two
Grassmannian variables.Comment: LaTeX file, 23 page
Cohomological Operators and Covariant Quantum Superalgebras
We obtain an interesting realization of the de Rham cohomological operators
of differential geometry in terms of the noncommutative q-superoscillators for
the supersymmetric quantum group GL_{qp} (1|1). In particular, we show that a
unique superalgebra, obeyed by the bilinears of fermionic and bosonic
noncommutative q-(super)oscillators of GL_{qp} (1|1), is exactly identical to
that obeyed by the de Rham cohomological operators. A set of discrete symmetry
transformation for a set of GL_{qp} (1|1) covariant superalgebras turns out to
be the analogue of the Hodge duality * operation of differential geometry. A
connection with an extended BRST algebra obeyed by the nilpotent (anti-)BRST
and (anti-)co-BRST charges, the ghost charge and a bosonic charge (which is
equal to the anticommutator of (anti-)BRST and (anti-)co-BRST charges) is also
established.Comment: LaTeX file, 21 page
BRST analysis of topologically massive gauge theory: novel observations
A dynamical non-Abelian 2-form gauge theory (with B \wedge F term) is endowed
with the "scalar" and "vector" gauge symmetry transformations. In our present
endeavor, we exploit the latter gauge symmetry transformations and perform the
Becchi-Rouet-Stora-Tyutin (BRST) analysis of the four (3 + 1)-dimensional (4D)
topologically massive non-Abelian 2-form gauge theory. We demonstrate the
existence of some novel features that have, hitherto, not been observed in the
context of BRST approach to 4D (non-)Abelian 1-form as well as Abelian 2-form
and 3-form gauge theories. We comment on the differences between the novel
features that emerge in the BRST analysis of the "scalar" and "vector" gauge
symmetries of the theory.Comment: LaTeX file, 14 pages, an appendix added, references expanded, version
to appear in EPJ
Brane-world Quantum Gravity
The Arnowitt-Deser-Misner canonical formulation of general relativity is
extended to the covariant brane-world theory in arbitrary dimensions. The
exclusive probing of the extra dimensions makes a substantial difference,
allowing for the construction of a non-constrained canonical theory. The
quantum states of the brane-world geometry are defined by the
Tomonaga-Schwinger equation, whose integrability conditions are determined by
the classical perturbations of submanifolds contained in the Nash's
differentiable embedding theorem. In principle, quantum brane-world theory can
be tested by current experiments in astrophysics and by near future laboratory
experiments at Tev energy. The implications to the black-hole information loss
problem, to the accelerating cosmology, and to a quantum mathematical theory of
four-sub manifolds are briefly commented.Comment: 14 pages, no figures, JHEP format, to appear in JHEP April 200
Verifying the Kugo-Ojima Confinement Criterion in Landau Gauge Yang-Mills Theory
Expanding the Landau gauge gluon and ghost two-point functions in a power
series we investigate their infrared behavior. The corresponding powers are
constrained through the ghost Dyson-Schwinger equation by exploiting
multiplicative renormalizability. Without recourse to any specific truncation
we demonstrate that the infrared powers of the gluon and ghost propagators are
uniquely related to each other. Constraints for these powers are derived, and
the resulting infrared enhancement of the ghost propagator signals that the
Kugo-Ojima confinement criterion is fulfilled in Landau gauge Yang-Mills
theory.Comment: 4 pages, no figures; version to be published in Physical Review
Letter
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