Towards a unification of gravity and Yang-Mills theory

TL;DR

This paper proposes a unified gauge-invariant theory combining gravity and Yang-Mills fields on phase space, reproducing known theories in specific limits and signatures, with potential implications for quantum gravity.

Contribution

It introduces a novel gauge and diffeomorphism invariant framework unifying gravity and Yang-Mills theories, applicable to arbitrary gauge groups and with a simple phase space metric.

Findings

Recovers Ashtekar gravity with cosmological constant for SO(3,C)

Reduces to conventional Yang-Mills theory in weak field limit

Real in Euclidean signature, complex in Lorentzian signature

Abstract

We introduce a gauge and diffeomorphism invariant theory on Yang-Mills phase space. The theory is well defined for an arbitrary gauge group with an invariant bilinear form, it contains only first class constraints, and the spacetime metric has a simple form in terms of the phase space variables. With gauge group $SO(3,C)$, the theory equals the Ashtekar formulation of gravity with a cosmological constant. For Lorentzian signature, the theory is complex, and we have not found any good reality conditions. In the Euclidean signature case, everything is real. In a weak field expansion around de Sitter spacetime, the theory is shown to give the conventional Yang-Mills theory to the lowest order in the fields.