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.
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.}
34369088
Infrared behavior of three- and four-gluon vertices in Yang-Mills theory.
7951171
Thermal matter and radiation in a gravitational field.
We study the one-loop contributions of matter and radiation to the gravitational polarization tensor at finite temperatures. Using the analytically continued imaginary-time formalism, the contribution of matter is explicitly given to next-to-leading (${T}^{2}$) order. We obtain an exact form for the contribution of radiation fields, expressed in terms of generalized Riemann $\ensuremath{\zeta}$ functions. A general expression is derived for the physical polarization tensor, which is independent of the parametrization of graviton fields. We investigate the effective thermal masses associated with the normal modes of the corresponding graviton self-energy.
42575729
Nonlinear electromagnetic interactions in thermal QED.
We examine the behavior of the nonlinear interactions between electromagnetic fields at high temperature. It is shown that, in general, the $\mathrm{ln}(T)$ dependence on the temperature of the Green functions is simply related to their UV behavior at zero temperature. We argue that the effective action describing the nonlinear thermal electromagnetic interactions has a finite limit as $T\ensuremath{\rightarrow}\ensuremath{\infty}$. This thermal action approaches, in the long wavelength limit, the negative of the corresponding zero-temperature action.
6412329
General solution of the Wess-Zumino consistency condition for Einstein gravity.
The Wess-Zumino consistency condition for four-dimensional Einstein gravity is investigated in the space of local forms involving the fields, the ghosts, the antifields and their derivatives. Its general solution is constructed for all values of the form degree and of the ghost number. It is shown in particular that the antifields (= sources for the BRST variations) can occur only through cohomologically trivial terms.