Riff-in-Thyme said:
these announcements are so,,,,,,,,, vague! But interesting progress.
The actual paper by Rodolfo Gambini and Jorge Pullin (at http://prl.aps.org/abstract/PRL/v110/i21/e211301 ) is less vague, but it’s not really possible to translate it into a form suitable for the non-specialist. Here’s the abstract:
We quantize spherically symmetric vacuum gravity without gauge fixing the diffeomorphism constraint. Through a rescaling, we make the algebra of Hamiltonian constraints Abelian, and therefore the constraint algebra is a true Lie algebra. This allows the completion of the Dirac quantization procedure using loop quantum gravity techniques. We can construct explicitly the exact solutions of the physical Hilbert space annihilated by all constraints. New observables living in the bulk appear at the quantum level (analogous to spin in quantum mechanics) that are not present at the classical level and are associated with the discrete nature of the spin network states of loop quantum gravity. The resulting quantum space-times resolve the singularity present in the classical theory inside black holes.
Basically, they’ve been able to develop a mathematical model in loop quantum gravity for a “toy” black hole (one that doesn’t have all the properties that we expect a real black hole to have), and in their model the black hole core is not of zero volume and infinite density.
Why is this such a big deal? Well, even though LQG was developed to handle extreme gravity environments actually developing mathematical models of such environments in it and proving that all your maths is legal is bloody difficult! To give a crude analogy, LQG is like a set of Lego blocks for making models of black holes, but actually getting your Lego constructions to stick together and not collapse on them selves is a major PITA. :)
Bear in mind that the black hole model they’ve constructed ignores an important property that we’re pretty sure actual spacetime possesses. And it’s a simple Schwarzschild black hole, so it has no spin (or electric charge), and we expect all physical black holes to have some spin. After all, neutron stars tend to spin : newly-formed neutron stars can spin many thousand times per second, and it’s expected that freshly-collapsed black holes will spin even faster.
Also, LQG is by no means a full Quantum Gravity theory – it’s a cut-down interim substitute that was created essentially as a stepping-stone on the road to full QG.
So at this stage, we have no idea how accurately this new black hole model portrays the properties of the real thing; it may be a mathematical fiction. So BC is still free to believe in actual singularities if he wishes to. :)