The Ramond sector of heterotic string field theory

Abstract

We attempt to construct the full equations of motion for the Neveu–Schwarz and the Ramond sectors of the heterotic string field theory. Although they are also non-polynomial in the Ramond string field Ψ, we can construct them order by order in Ψ. Their explicit forms with the gauge transformations are given up to the next-to-next-to-leading order in Ψ. We also determine a subset of the terms to all orders. By introducing an auxiliary Ramond string field Ξ, we construct a covariant action supplemented with a constraint, which should be imposed on the equations of motion. We propose the Feynman rules and show how they reproduce well-known physical four-point amplitudes with external fermions.