New 2D dilaton gravity for nonsingular black holes

Understand

We construct a two-dimensional action that is an extension of spherically symmetric Einstein-Lanczos-Lovelock gravity.

• The action contains arbitrary functions of the areal radius and the norm squared of its gradient, but the field equations are second order and obey Birkhoff's theorem.
• In complete analogy with spherically symmetric Einstein-Lanczos-Lovelock gravity, the field equations admit the generalized Misner-Sharp mass as the first integral that determines the form of the vacuum solution.
• The arbitrary functions in the action allow for vacuum solutions that describe a larger class of interesting nonsingular black-hole spacetimes than previously available.