Fiorenzo Bastianelli

Chiral bosons coupled to supergravity

Abstract A single chiral boson, described in flat two-dimensional spacetime by a local lagrangian previously proposed by Floreanini and Jackiw, is coupled to supergravity. Nonlinear σ-models with chiral bosons coupled to gravity are also discussed.

Superstring anomalies in the semi-light-cone gauge

Abstract We compute the Einstein, Lorentz and Weyl worldsheet anomalies and the super-Poincare space-time anomalies of the heterotic superstring, using path-integrals and the gauge Γ + Θ =0 to fix the local fermionic κ -symmetry. The regulators for the various jacobians are all obtained from a recent general method of constructing consistent regulators. We do not use a special gauge for the metric. A general lemma for anomalies of algebraic and non-algebraic symmetries is obtained. Our results show that only for a certain class of metrics do all worldsheet and space-time anomalies cancel simultaneously after adding a suitable but complicated set of counterterms.

BRST symmetry from a change of variables and the gauged WZNW model

Abstract A lagrangian BRST formalism for treating the change of variables in the path integral is derived and applied to the case of the gauged WZNW model. The proposed method provides a derivation of the BRST charge for such a model.

Ward identities for quantum field theories with external fields

The effective action Γ for a quantum action S depending on quantum fields ψa and external fields Xα is shown to satisfy the following Ward identity: ∂Γ∂ψa[δψa]·Γ+∂S∂Xα δXα·Γ=−iℏ[Δ]·Γ Here δψa and δχα are (local or rigid) symmetries of S and [Ω] · Γ denotes all 1PI graphs with precisely one in setion of the local operator Ω. Δ parametrizes the anomalies. An example is given.

On chiral bosonization

Abstract We examine the bosonization of chiral fermions in a gravitational background, using a path integral approach. The bosonic model is given by an action proposed some time ago by Floreanini and Jackiw, suitably coupled to gravity. We use a regulator for the path integral measure obtained from the general construction of Diaz, Hatsuda, Troost, van Nieuwenhuizen and Van Proeyen. We show that the effective actions are identical.