10157623
Structure of the graviton self-energy at finite temperature
We study the graviton self-energy function in a general gauge, using a hard thermal loop expansion which includes terms proportional to T^4, T^2 and log(T). We verify explicitly the gauge independence of the leading T^4 term and obtain a compact expression for the sub-leading T^2 contribution. It is shown that the logarithmic term has the same structure as the ultraviolet pole part of the T=0 self-energy function. We argue that the gauge-dependent part of the T^2 contribution is effectively canceled in the dispersion relations of the graviton plasma, and present the solutions of these equations.
43000553
Multiparticle tree amplitudes in scalar field theory.
Following an argument advanced by Feynman, we consider a method for obtaining the effective action which generates the sum of tree diagrams with external physical particles. This technique is applied, in the unbroken \ensuremath{\lambda}${\mathrm{\ensuremath{\varphi}}}^{4}$ theory, to the derivation of the threshold amplitude for the production of n scalar particles by n initial particles. The leading contributions to the tree amplitude, which become singular in the threshold limit, exhibit a factorial growth with n. \textcopyright{} 1996 The Physical Society.
44515091
Thermal Operator Representation of Finite Temperature Graphs II
F. T. Brandt, Ashok Das, Olivier Espinosa, J. Frenkel and Silvana Perez a Instituto de F́ısica, Universidade de São Paulo, São Paulo, BRAZIL b Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627-0171, USA c Departamento de F́ısica, Universidad Técnica Federico Santa Maŕıa, Casilla 110-V, Valparáıso, CHILE and d Departamento de F́ısica, Universidade Federal do Pará, Belém, Pará 66075-110, BRAZIL
119875841
Cancellation of soft interactions with spectators in the Drell-Yan process
Abstract We verify by explicit calculation, to 2-loop order, the cancellation of soft interactions with spectators in the Drell-Yan process. We employ a model in which a “meson” consists of a parton and a spectator parton, each moving along parallel eikonal lines. The process occurs in the collision of two such “mesons” at velocities near the speed of light. The calculation is sensitive to gluons with wavelengths of the order of or greater than the meson size.
119048914
The Static effective action for noncommutative QED at high temperature
In this paper, we systematically study the effective action for non-commutative QED in the static limit at high temperature. When $\theta p^{2}\ll 1$, where $\theta$ represents the magnitude of the parameter for non-commutativity and $p$ denotes a typical external three momentum, we show that this leads naturally to a derivative expansion in this model. The study of the self-energy, in this limit, leads to nontrivial $\theta$ dependent corrections to the electric and magnetic masses, which exist only above a certain critical temperature. The three point and the four point amplitudes are also studied as well as their relations to the Ward identities in this limit. We determine the closed form expression for the current involving only the spatial components of the gauge field and present the corresponding static effective action, which is gauge invariant.
35897734
Nonlinear couplings and tree amplitudes in gauge theories.
Following a remark advanced by Feynman, we study the connection between the form of the nonlinear vertices involving gauge particles and the Abelian gauge invariance of physical tree amplitudes. We show that this requirement, together with some natural assumptions, fixes uniquely the structure of the Yang-Mills theory. However, the constraints immposed by the above property are not sufficient to single out the gauge theory of gravitation. {copyright} {ital 1996 The American Physical Society.}
14272321
Local BRST Cohomology and Covariance

Abstract:The paper provides a framework for a systematic analysis of the local BRST cohomology in a large class of gauge theories. The approach is based on the cohomology of s+d in the jet space of fields and antifields, s and d being the BRST operator and exterior derivative respectively. It relates the BRST cohomology to an underlying gauge covariant algebra and reduces its computation to a compactly formulated problem involving only suitably defined generalized connections and tensor fields. The latter are shown to provide the building blocks of physically relevant quantities such as gauge invariant actions, Noether currents and gauge anomalies, as well as of the equations of motion.
15946600
Actions and symmetries of NSR superstrings and D-strings
Abstract We present all NSR superstring and super-D-string actions invariant under a set of prescribed gauge transformations, and characterize completely their global symmetries. In particular we obtain locally supersymmetric Born–Infeld actions on general backgrounds in a formulation with extra target space dimensions. The nontrivial global symmetries of the superstring actions correspond to isometries of the background, whereas super-D-string actions can have additional symmetries acting nontrivially also on the coordinates of the extra dimensions.
14338539
Deformations of global symmetries in the extended antifield formalism
It is outlined how deformations of field theoretical rigid symmetries can be constructed and classified by cohomological means in the extended antifield formalism. Special attention is devoted to deformations referring only to a subset of the rigid symmetries of a given model and leading to a nontrivial extension of the graded Lie algebra associated with that subset. The method is illustrated for a D=4, N=2 supersymmetric model where the central extension of the supersymmetry algebra emerges via a deformation. Deformations of gauge fixed actions with a BRST symmetry are discussed too and illustrated by the Curci–Ferrari model.
15471713
Lectures on Supergravity
The text is an essentially self-contained introduction to four-dimensional N=1 supergravity, including its couplings to super Yang-Mills and chiral matter multiplets, for readers with basic knowledge of standard gauge theories and general relativity. Emphasis is put on showing how supergravity fits in the general framework of gauge theories and how it can be derived from a tensor calculus for gauge theories of a standard form.
16321193
Structure of BRS-Invariant Local Functionals
For a large class of gauge theories a nilpotent BRS-operator $s$ is constructed and its cohomology in the space of local functionals of the off-shell fields is shown to be isomorphic to the cohomology of $\4s=s+d$ on functions $f(\4C,\PH)$ of tensor fields $\PH$ and of variables $\4C$ which are constructed of the ghosts and the connection forms. The result allows general statements about the structure of invariant classical actions and anomaly candidates whose BRS-variation vanishes off-shell. The assumptions under which the result holds are thoroughly discussed.