Novel black-bounce spacetimes: Wormholes, regularity, energy conditions, and causal structure

We develop a number of novel "black-bounce" spacetimes. These are specific regular black holes where the "area radius" always remains non-zero, thereby leading to "throat" that is either timelike (corresponding traversable wormhole), spacelike "bounce" into future universe), or null "one-way wormhole"). shall first perform general analysis regularity conditions for such spacetime, and then consider examples. The examples constructed using mass function similar Fan--Wang, fall several particular cases, as original Simpson--Visser model, Bardeen-type other generalizations thereof. analyse regularity, energy conditions, causal structure these models. main results new geometries, more complex than before, with two horizons, possibility an extremal case. derive theorem regarding static space-time another (non)-satisfaction classical conditions.