Light-Front Higher-Spin Theories in Flat Space

TL;DR

This paper explores light-front higher-spin theories in flat space, demonstrating new interaction vertices, gravitational couplings, and a chiral higher-spin theory with vanishing four-point amplitudes, challenging previous no-go theorems.

Contribution

It introduces a light-cone approach to higher-spin interactions, revealing new vertices, gravitational couplings, and a complete chiral higher-spin theory with perturbative locality.

Findings

Existence of two-derivative gravitational couplings for higher-spin fields

Construction of a chiral higher-spin theory with vanishing four-point amplitude

Reconstruction of the scalar quartic vertex in unitary higher-spin theory

Abstract

We revisit the problem of interactions of higher-spin fields in flat space. We argue that all no-go theorems can be avoided by the light-cone approach, which results in more interaction vertices as compared to the usual covariant approaches. It is stressed that there exist two-derivative gravitational couplings of higher-spin fields. We show that some reincarnation of the equivalence principle still holds for higher-spin fields - the strength of gravitational interaction does not depend on spin. Moreover, it follows from the results by Metsaev that there exists a complete chiral higher-spin theory in four dimensions. We give a simple derivation of this theory and show that the four-point scattering amplitude vanishes. Also, we reconstruct the quartic vertex of the scalar field in the unitary higher-spin theory, which turns out to be perturbatively local.