226 research outputs found
Gauge parameter dependence in the background field gauge and the construction of an invariant charge
By using the enlarged BRS transformations we control the gauge parameter
dependence of Green functions in the background field gauge. We show that it is
unavoidable -- also if we consider the local Ward identity -- to introduce the
normalization gauge parameter , which enters the Green functions of
higher orders similarly to the normalization point . The dependence of
Green functions on is governed by a further partial differential
equation. By modifying the Ward identity we are able to construct in 1-loop
order a gauge parameter independent combination of 2-point vector and
background vector functions. By explicit construction of the next orders we
show that this combination can be used to construct a gauge parameter
independent RG-invariant charge. However, it is seen that this RG-invariant
charge does not satisfy the differential equation of the normalization gauge
parameter , and, hence, is not -independent as required.Comment: 29 pages, LaTe
Staggered fermions and their improvements
Expanding upon the arguments of Sharpe, we explicitly implement the Symanzik
improvement program demonstrating the absence of order terms in the
staggered fermion action. We propose a general program to improve fermion
operators to remove corrections from their matrix elements, and
demonstrate this program for the examples of matrix elements of fermion
bilinears and . We also determine the additional operators which must be
added to improve the staggered fermion currents.Comment: 3 pages, talk presented at LATTICE'96(Improvement
Bosonization and even Grassmann variables
A new approach to bosonization in relativistic field theories and many-body
systems, based on the use of fermionic composites as integration variables in
the Berezin integral defining the partition function of the system, is tested.
The method is applied to the study of a simplified version of the BCS model.Comment: 20 pages, LaTe
Supersymmetric renormalization prescription in N = 4 super-Yang--Mills theory
Using the shadow dependent decoupled Slavnov-Taylor identities associated to
gauge invariance and supersymmetry, we discuss the renormalization of the N=4
super-Yang-Mills theory and of its coupling to gauge-invariant operators. We
specify the method for the determination of non-supersymmetric counterterms
that are needed to maintain supersymmetry
The Coupling of Chern-Simons Theory to Topological Gravity
We couple Chern-Simons gauge theory to 3-dimensional topological gravity with
the aim of investigating its quantum topological invariance. We derive the
relevant BRST rules and Batalin-Vilkovisky action. Standard BRST
transformations of the gauge field are modified by terms involving both its
anti-field and the super-ghost of topological gravity. Beyond the obvious
couplings to the metric and the gravitino, the BV action includes hitherto
neglected couplings to the super-ghost. We use this result to determine the
topological anomalies of certain higher ghost deformations of SU(N)
Chern-Simons theory, introduced years ago by Witten. In the context of
topological strings these anomalies, which generalize the familiar framing
anomaly, are expected to be cancelled by couplings of the closed string sector.
We show that such couplings are obtained by dressing the closed string field
with topological gravity observables.Comment: 39 pages, LaTex; references added, typos corrected, version to appear
in Nucl. Phys.
The spectrum of lattice QCD with staggered fermions at strong coupling
Using 4 flavors of staggered fermions at infinite gauge coupling, we compare
various analytic results for the hadron spectrum with exact Monte Carlo
simulations. Agreement with Ref. \cite{Martin_etal} is very good, at the level
of a few percent.
Our results give credence to a discrepancy between the baryon mass and the
critical chemical potential, for which baryons fill the lattice at zero
temperature and infinite gauge coupling. Independent determinations of the
latter set it at about 30% less than the baryon mass. One possible explanation
is that the nuclear attraction becomes strong at infinite gauge coupling.Comment: 11 pages, 3 figure
Remarks on the renormalization of gauge invariant operators in Yang-Mills theory
A simplified proof of a theorem by Joglekar and Lee on the renormalization of
local gauge invariant operators in Yang-Mills theory is given. It is based on
(i) general properties of the antifield-antibracket formalism; and (ii)
well-established results on the cohomology of semi-simple Lie algebras.Comment: 12 pages in LaTex, ULB-PMIF/93-0
Quark Effects in the Gluon Condensate Contribution to the Scalar Glueball Correlation Function
One-loop quark contributions to the dimension-four gluon condensate term in
the operator product expansion (OPE) of the scalar glueball correlation
function are calculated in the MS-bar scheme in the chiral limit of quark
flavours. The presence of quark effects is shown not to alter the cancellation
of infrared (IR) singularities in the gluon condensate OPE coefficients. The
dimension-four gluonic condensate term represents the leading power corrections
to the scalar glueball correlator and, therein, the one-loop logarithmic
contributions provide the most important condensate contribution to those QCD
sum-rules independent of the low-energy theorem (the subtracted sum-rules).Comment: latex2e, 6 pages, 7 figures embedded in latex fil
Gauge Independence of the Effective Potential Revisited
We apply the formalism of extended BRS symmetry to the investigation of the
gauge dependence of the effective potential in a spontaneously symmetry broken
gauge theory. This formalism, which includes a set of Grassmann parameters
defined as the BRS variations of the gauge-fixing parameters, allows us to
derive in a quick and unambiguous way the related Nielsen identities, which
express the physical gauge independence, in a class of generalized 't Hooft
gauges, of the effective potential. We show in particular that the validity of
the Nielsen identities does not require any constraint on the gauge-fixing
parameters, to the contrary of some claims found in the literature. We use the
method of algebraic renormalization, which leads to results independent of the
particular renormalization scheme used.Comment: 13 pages, no figures, Latex, final version published in NP
Homological Algebra and Yang-Mills Theory
The antifield-BRST formalism and the various cohomologies associated with it
are surveyed and illustrated in the context of Yang-Mills gauge theory. In
particular, the central role played by the Koszul-Tate resolution and its
relation to the characteristic cohomology are stressed.Comment: 20 pages in LaTe
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