New proper tetrad for teleparallel gravities in non-flat spacetime

TL;DR

This paper introduces a new proper tetrad in teleparallel gravity that removes inertial effects, leading to different solutions and behaviors in strong fields, and clarifies the non-uniqueness of proper tetrads.

Contribution

It constructs a novel proper tetrad for teleparallel gravities, demonstrating its differences from previous choices and exploring its implications for solutions in strong gravitational fields.

Findings

The new tetrad differs from previously used ones in behavior and solutions.

It enables finding solutions in the strong field regime.

In flat spacetime, it reduces to the known tetrad.

Abstract

The restoration of spin connection clarifies the long known local Lorentz invariance problem in telelparallel gravities. It is considered now that any tetrad together with the associated spin connection can be equally utilized. Among the tetrads there is a particular one, namely proper tetrad, in which all the spurious inertial effects are removed and the spin connection vanishes. A specific tetrad was proposed in the literature for spherically symmetric cases, which has been used in regularizing the action, as well as in searching solutions in various scenarios. We show in this paper that the this tetrad is not the unique choice for the proper tetrad. We construct a new tetrad that can be considered as the proper one, and it will lead to different behaviors of the field equation and results in different solutions. With this proper tetrad, it is possible to find solutions to teleparallel gravities in the strong field regime, which may have physical applications. In the flat spacetime limit, the new tetrad coincides with the aforementioned one.