Teleparallel spin connection can regularize gravitational action, authors show using the Schwarzschild black hole
The paper shows that a quantity called the teleparallel spin connection can act like a counterterm and make the gravitational action finite. In the teleparallel formulation of gravity, the core variables are a tetrad (a local set of reference frames) and a pure‑gauge spin connection (a choice that does not affect the field equations). When the spin connection is chosen to match the tetrad, its contribution to the action appears as a surface term. The authors argue that this surface term can regularize the divergent parts of the action, replacing the familiar counterterm methods used in standard general relativity.
Teleparallel gravity differs from the usual Riemannian view because its action does not contain second derivatives of the metric. That means one does not need the usual Gibbons–Hawking–York boundary term to make variational problems well defined. Instead, the action depends on the tetrad and the non‑dynamical spin connection. The paper uses the covariant teleparallel formulation, where both objects appear explicitly. The main technical point is that the spin connection contributes only through a boundary, or surface, term that can cancel the divergences of the bulk integral.
To test and clarify this idea the authors study the Schwarzschild spacetime, the standard black‑hole solution. They distinguish two ways to compute the action: as a bulk integral over the spacetime volume, and as a quasilocal quantity obtained by rewriting the bulk integral as a surface term. They show the apparent disagreement between some earlier teleparallel results and the standard general‑relativistic results stems from neglecting contributions tied to the spacetime singularity at the center. The quasilocal (surface) action does include that central contribution and then agrees with the usual results from general relativity. This resolves prior puzzles noted in the literature, where some choices gave twice or even three times the expected value when evaluated as a volume integral.