Properties of the spherically symmetric polymer black holes
  In this paper we systematically study a five-parameters class of spherically
symmetric polymer black/white hole solutions, and find that only three
independent combinations are physical and uniquely determine the spacetime
properties. After exploring the whole 3-dimensional (3D) phase space, we find
that the model has very rich physics, and depending on the choice of these
parameters, various possibilities exist, including: (i) spacetimes that have
the standard black/white hole structures, that is, spacetimes that are free of
spacetime curvature singularities and possess two asymptotically flat regions,
which are connected by a transition surface (throat) with a finite and non-zero
geometric radius. The black/white hole masses measured by observers in the two
asymptotically flat regions are all positive, and the surface gravity of the
black (white) hole is positive (negative). (ii) Spacetimes that have
wormhole-like structures, in which the two masses are all positive, but no
horizons exist.(iii) Spacetimes that still possess curvature singularities,
which can be either hidden inside trapped regions or naked. However, such
spacetimes correspond to only some limit cases, and the necessary (but not
sufficient) condition is that at least one of the two "polymerization"
parameters vanishes. In addition, even for solar mass black/white holes,
quantum gravitational effects can be still very large at the black/white hole
horizons, again depending on the choice of the parameters.
