ANEC on stress-tensor states in perturbative λ ϕ 4 theory

Abstract

We evaluate the Average Null Energy Condition (ANEC) on momentum eigenstates generated by the stress tensor in perturbative λ ϕ4 and general spacetime dimension. We first compute the norm of the stress-tensor state at second order in λ; as a by-product of the derivation we obtain the full expression for the stress tensor 2-point function at this order. We then compute the ANEC expectation value to first order in λ, which also depends on the coupling of the stress-tensor improvement term ξ. We study the bounds on these couplings that follow from the ANEC and unitarity at first order in perturbation theory. These bounds are stronger than unitarity in some regions of coupling space.