Aspects and applications of nonlocal Lorentz-violation

TL;DR

This paper investigates nonlocal, Lorentz-violating scalar theories that are ghost-free and unitary, proposing a low-scale nonlocal dark sector that could produce observable long-range forces and interact weakly with the standard model.

Contribution

It introduces a novel class of nonlocal, Lorentz-violating scalar theories that are both ghost-free and unitary, and models a dark sector communicating with the standard model through heavy fermions.

Findings

Theories are ghost-free and unitary in Minkowski space.

A framework for a nonlocal, Lorentz-violating dark sector interacting weakly with the standard model.

Potential for observable long-range forces from the dark sector.

Abstract

We consider simple scalar theories with quadratic terms that are nonlocal and Lorentz violating. Unlike similar Lorentz-invariant nonlocal theories that we have considered previously, the theories studied here are both ghost-free and unitary as formulated in Minkowski space. We explore the possibility that the scale of nonlocality could be low in a dark sector, where the stringent constraints on the violation of Lorentz invariance may be accommodated via the weak coupling to the standard model. We point out that long-range forces may originate from such a sector and be distinguishable from more conventional beyond-the-standard model possibilities. We present a model in which a nonlocal, Lorentz-violating dark sector communicates with the standard model via a sector of heavy vector-like fermions, a concrete framework in which phenomenological constraints and signals can be investigated.