Composite Gravitons from Metric-Independent Quantum Field Theories

TL;DR

This paper reviews recent developments in composite graviton theories within metric-independent quantum field frameworks, clarifying the conditions for massless gravitons and proposing ghost-free models without limiting procedures.

Contribution

It clarifies the tunings needed for massless composite gravitons and introduces related ghost-free theories that do not rely on massless limits.

Findings

Clarified the meaning of tunings for massless gravitons.

Proposed ghost-free models without Pauli-Fierz mass terms.

Discussed potential ultraviolet completions for these theories.

Abstract

We review some recent work by Carone, Erlich and Vaman on composite gravitons in metric-independent quantum field theories, with the aim of clarifying a number of basic issues. Focusing on a theory of scalar fields presented previously in the literature, we clarify the meaning of the tunings required to obtain a massless graviton. We argue that this formulation can be interpreted as the massless limit of a theory of massive composite gravitons in which the graviton mass term is not of Pauli-Fierz form. We then suggest closely related theories that can be defined without such a limiting procedure (and hence without worry about possible ghosts). Finally, we comment on the importance of finding a compelling ultraviolet completion for models of this type, and discuss some possibilities.