Seiberg--Witten maps for $\boldsymbol{SO(1,3)}$ gauge invariance and deformations of gravity

Abstract

A family of diffeomorphism-invariant Seiberg--Witten deformations of gravity is constructed. In a first step Seiberg--Witten maps for an SO(1,3) gauge symmetry are obtained for constant deformation parameters. This includes maps for the vierbein, the spin connection and the Einstein--Hilbert Lagrangian. In a second step the vierbein postulate is imposed in normal coordinates and the deformation parameters are identified with the components $\theta^{\mu\nu}(x)$ of a covariantly constant bivector. This procedure gives for the classical action a power series in the bivector components which by construction is diffeomorphism-invariant. Explicit contributions up to second order are obtained. For completeness a cosmological constant term is included in the analysis. Covariant constancy of $ \theta^{\mu\nu}(x) $, together with the field equations, imply that, up to second order, only four-dimensional metrics which are direct sums of two two-dimensional metrics are admissible, the two-dimensional curvatures being expressed in terms of $\theta^{\mu\nu}$. These four-dimensional metrics can be viewed as a family of deformed emergent gravities.