Warren Siegel

Supersymmetric dimensional regularization via dimensional reduction

We introduce a modified form of dimensional regularization which manifestly preserves gauge invariance, unitarity, and global supersymmetry. The prescription is that the action which results from analytic continuation to lower dimensions is that found by dimensional reduction. We also consider its application to supergravity.

Improved methods for supergraphs

We introduce some new techniques into superfield perturbation theory which allow considerable simplifications in calculations. As a result, we show that all contributions to the effective action can be written as integrals over a single d4θ. We also give the background group field formalism for supersymmetric non-abelian gauge theories. To illustrate our methods, we give examples of loop calculations: in particular, we show that in O(4) extended supersymmetric non-abelian gauge theories all one-loop propagator corrections cancel identically (both infinite and finite parts) and that these theories, at one loop, are finite and have no renormalizations (in the Fermi-Feynman gauge).

Two-vierbein formalism for string-inspired axionic gravity.

Using independent left and right vierbeins to describe a graviton plus axion as suggested by string mechanics, O(d,d) duality is realized linearly

Hidden local supersymmetry in the supersymmetric particle action

Abstract The action for a massless supersymmetric particle in terms of superspace coordinates x a (τ) and θ α (τ) is found to be invariant under a local supersymmetry which allows half of θ to be gauged away.

Bouncing universes in string-inspired gravity

We consider the effects on cosmology of higher-derivative modifications of (effective) gravity that make it asymptotically free without introducing ghosts. The weakening of gravity at short distances allows pressure to prevent the singularity, producing a solution with contraction preceding expansion.

Gauge String Fields

Abstract Gauge-invariant actions for free bosonic string fields are derived from the corresponding BRST-invariant gauge-fixed action. The auxiliary components needed to make the action local and maintain unconstrained gauge invariance arise from an SU(1,1)-invariant sector of a pair of opposite-metric fermionic string coordinates or of an extra timelike bosonic one.

Manifest Lorentz invariance sometimes requires non-linearity☆

Abstract Manifestly Lorentz-invariant actions for self-dual antisymmetric-tensor gauge fields are found by using cubic Lagrange-multiplier terms. The Lagrange-multiplier fields are not dynamical, and can be eliminated to obtain a quadratic light-cone action.

Classical Superstring Mechanics

Abstract We describe the classical mechanics of the superstring in both hamiltonian and lagrangian formulations, including massless external fields. The formulation is a modification of that of Green and Schwarz that allows supersymmetric Lorentz covariant quantization.

Unextended Superfields in Extended Supersymmetry

In extended supersymmetry, we discuss the advantages of unextended superfields over extended ones and component fields. We show how to derive from the extended formalism the unextended superfields, and their extended supersymmetry transformations in unextended-superfield form.

Gauge spinor superfield as scalar multiplet

Abstract A chiral spinor superfield, with an appropriate gauge invariance, describes a scalar multiplet consisting of a scalar, an antisymmetric-tensor gauge field, a Weyl spinor, and no auxiliary fields.