17958246
Seiberg-Witten Maps and Anomalies in Noncommutative Yang-Mills Theories
A BRST-cohomological analysis of Seiberg-Witten maps and results on gauge anomalies in noncommutative Yang-Mills theories with general gauge groups are reviewed.
16423561
Covariant theory of asymptotic symmetries, conservation laws and central charges
Under suitable assumptions on the boundary conditions, it is shown that there is a bijective correspondence between equivalence classes of asymptotic reducibility parameters and asymptotically conserved (n−2)-forms in the context of Lagrangian gauge theories. The asymptotic reducibility parameters can be interpreted as asymptotic Killing vector fields of the background, with asymptotic behaviour determined by a new dynamical condition. A universal formula for asymptotically conserved (n−2)-forms in terms of the reducibility parameters is derived. Sufficient conditions for finiteness of the charges built out of the asymptotically conserved (n−2)-forms and for the existence of a Lie algebra g among equivalence classes of asymptotic reducibility parameters are given. The representation of g in terms of the charges may be centrally extended. An explicit and covariant formula for the central charges is constructed. They are shown to be 2-cocycles on the Lie algebra g. The general considerations and formulas are applied to electrodynamics, Yang–Mills theory and Einstein gravity.
116908765
Gauge Covariant Algebras and Local BRST Cohomology
The formulation of the local BRST cohomology on infinite jet bundles and its relation and reduction to gauge covariant algebras are reviewed. As an illustration, we compute the local BRST cohomology for geodesic motion in (pseudo-) Riemannian manifolds and discuss briefly the result (symmetries, constants of the motion, consistent deformations).
119057407
Extended antifield formalism
Abstract The antifield formalism is extended so as to incorporate the rigid symmetries of a given theory. To that end, it is necessary to introduce global ghosts not only for the given rigid symmetries, but also for all the higher order conservation laws, associated with conserved antisymmetric tensors j μ 1 3 μ k fulfilling ϖ μ 1 j μ 1 3 μ k 2~ 0. Otherwise, one may encounter obstructions of the type discussed in by the authors. These higher order conservation laws are shown to define additional rigid symmetries of the master equation and to form — together with the standard symmetries — an interesting algebraic structure. They lead furthermore to independent Ward identities which are derived in the standard manner, because the resulting master (“Zinn-Justin”) equation capturing both the gauge symmetries and the rigid symmetries of all orders takes a known form. Issues such as anomalies or consistent deformations of the action preserving some set of rigid symmetries can be also systematically analysed in this framework.
120563531
The gravitational anomalies
Abstract We determine all solutions to the consistency equations which have to be satisfied by anomalies in gravitational theories with a Poincare-invariant ground state.
118395460
Nonpolynomial gauge invariant interactions of 1-form and 2-form gauge potentials
A four dimensional gauge theory with nonpolynomial but local interactions of 1-form and 2-form gauge potentials is constructed. The model is a nontrivial deformation of a free gauge theory with nonpolynomial dependence on the deformation parameter (= gauge coupling constant).
119502016
Dispersion relations for the self-energy in noncommutative field theories
We study the IR/UV connection in non-commutative $\phi^{3}$ theory as well as in non-commutative QED from the point of view of the dispersion relation for the self-energy. We show that, although the imaginary part of the self-energy is well behaved as the parameter of non-commutativity vanishes, the real part becomes divergent as a consequence of the high energy behavior of the dispersion integral. Some other interesting features that arise from this analysis are also briefly discussed.
16723250
Generalized forward scattering amplitudes in QCD at high temperature
We extend to a general class of covariant gauges an approach which relates the thermal Green functions to forward scattering amplitudes of thermal particles. A brief discussion of the nontransversality of the thermal gluon polarization tensor is given in this context. This method is then applied to the calculation of the ln(T) contributions associated with general configurations of two- and three-point gluon functions. The results are Lorentz covariant and have the same structure as the ultraviolet divergent contributions which occur at zero temperature. {copyright} {ital 1997} {ital The American Physical Society}
14070716
Absence of higher order corrections to the non-Abelian Chern–Simons coefficient
Abstract We extend the Coleman–Hill analysis to non-Abelian Chern–Simons theories containing a tree level topological mass term. We show, in the case of a pure Yang–Mills–Chern–Simons theory, that there are no corrections to the coefficient of the Chern–Simons term beyond one loop in the axial gauge. Our arguments use constraints coming only from small gauge Ward identities as well as the analyticity of the amplitudes, much like the proof in the Abelian case. Some implications of this result are also discussed.
8551567
The Boltzmann Equation in Scalar Field Theory
We derive the classical transport equation, in scalar field theory with a g2V(ϕ) interaction, from the equation of motion for the quantum field. We obtain a very simple, but iterative, expression for the effective action Γ which generates all the n-point Green functions in the high-temperature limit. An explicit and closed form is given for Γ in the static case.
18378024
High-temperature qcd and the classical boltzmann equation in curved spacetime
Abstract It has been shown that the high-temperature limit of perturbative thermal QCD is easily obtained from the Boltzmann transport equation for “classical” coloured particles [P.F. Kelly et al., Phys. Rev. D 50 (1994) 4209]. We generalize this treatment to curved space-time. We are thus able to construct the effective stress-energy tensor. We give a construction for an effective action. As an example of the convenience of the Boltzmann method, we derive the high-temperature 3-graviton function. We discuss the static case.