Lorentzian Goldstone modes shared among photons and gravitons

TL;DR

This paper develops an emergent electrogravity theory where photons and gravitons are shared Goldstone modes resulting from spontaneous Lorentz invariance violation, revealing novel symmetry structures and potential Lorentz and CPT violations.

Contribution

It introduces a unified emergent electrogravity model combining QED and tensor gravity with higher global symmetries, leading to shared Goldstone modes for photons and gravitons.

Findings

Shared Goldstone modes among photons and gravitons.

SLIV effects cancel at lowest order processes.

Higher global symmetry $SO(7,3)$ underlies the tensor field constraint.

Abstract

It has long been known that photons and gravitons may appear as vector and tensor Goldstone modes caused \ by spontaneous Lorentz invariance violation (SLIV). Usually this approach is considered for photons and gravitons separately. We develop the emergent electrogravity theory consisting of the ordinary QED and the tensor field gravity model which mimics the linearized general relativity in Minkowski spacetime. In this theory, Lorentz symmetry appears incorporated into higher global symmetries of the length-fixing constraints put on the vector and tensor fields involved, $A_{\mu }^{2}=\pm M_{A}^{2}$ and $H_{\mu \nu }^{2}=\pm M_{H}^{2}$ ($M_{A}$ and $M_{H}$ are the proposed symmetry breaking scales). We show that such a SLIV pattern being related to breaking of global symmetries underlying these constraints induces the massless Goldstone and pseudo-Goldstone modes shared among photon and graviton. While for a vector field case the symmetry of the constraint coincides with Lorentz symmetry $SO(1,3)$ of the electrogravity Lagrangian, the tensor field constraint itself possesses much higher global symmetry $SO(7,3)$, whose spontaneous violation provides a sufficient number of zero modes collected in a graviton. Accordingly, while photon may only contain true Goldstone modes, graviton appears at least partially composed from pseudo-Goldstone modes rather than from pure Goldstone ones. When expressed in terms of these modes, the theory looks essentially nonlinear and contains a variety of Lorentz and $CPT$ violating couplings. However, all SLIV effects turn out to be strictly cancelled in the lowest order processes that is considered in some detail. How this emergent electrogravity theory could be observationally differed from conventional QED and GR theories is also briefly discussed.