Hi,

LQG predicts that the Big Bang was actually a ‘Big Bounce’, not a singularity but a continuum, where the collapse of a previous universe spawned the creation of ours.

Read more at: https://phys.org/news/2012-07-big_1.html

https://en.wikipedia.org/wiki/Big_Bounce

Oh, I see. Thank you very much, Prof Alexander, for the great feedback. I'll go through for the Big Bounce phenomenon. 

Philadelphia, PA

Dear all, 

Interesting question. 

I think that, as a general matter, it is among the valid or more plausible desiderata of theories of quantum gravity to avoid the singularities of General Relativity. One finds this point in Hawking's writings, for instance. The singularity of General Relativity would be an infinitesimal point of infinite density --and it is not avoided by changing the frame of reference. Surely, any such thing is unphysical.

Partly in consequence, additional physics for very small probing lengths and very high energies is wanted to provide an alternative account --say, of what happens with the collapse of a massive star into a black hole. The idea of the "quantum bounce," is an alternative to the singularities of GR. It is formulated, often enough, by analogy with how various QM phenomena become involved in resisting the final collapse of a massive star--as with the Pauli exclusion principle, e.g. If one were to accept the idea of the quantum bounce in cosmology, regarding the big bang, then the same must be true with the final collapse of a massive star into a black hole--the singularity of GR would be resisted by fundamental quantum indeterminacy. 

So far the plausibilities. But I have noticed a certain sensitivity in LQG regarding this point. I think there is very good (indirect) evidence of black holes. Plans are presently afoot for direct observation. Apparently, there is a super-massive black hole at the center of almost every galaxy. I understand that there is also good evidence of stellar sized black holes from local gravitational lensing. But if the evidence of black holes is relatively strong, still the evidence of "white holes" is pretty weak--and that is the point of sensitivity. Given LQG, if there are black holes, then there should also be white holes resulting from the quantum bounce. Various astrophysical phenomena, such a gamma ray bursts are possible candidates for the white holes, but the possible evidence seems to generally be open to other plausible explanations. Lacking firmer evidence of white holes, it seems that LQG and the quantum bounce are left hanging. Or, at the least, that is my impression of the present state of the evidence.

Of course theories of quantum gravity generally suffer with similar problems. But I wonder, in particular, what others might have to say about this problem of the missing white holes.

H.G. Callaway 

Big bang or Big bounce: How was our universe born?. Available from: https://www.researchgate.net/post/Big_bang_or_Big_bounce_How_was_our_universe_born [accessed Apr 19, 2017].

Thank you so much, Prof H. G. Callaway, for the feedback. I will go through from the article stated. 

@Callaway, "the singularity of GR would be resisted by fundamental quantum indeterminacy" you may not need to go to QM. a black hole is an optical element for spacetime geodesics. that's the optics but in reality there are waves that interfere and obscure such singularities. as you have a resolution limit for a lense -- the Airy disk -- you have a horizon for the black hole. otherwise put: if the Huygens principle is still valid for gravitational waves then they will interfere. should this be a completely destructive interference pattern the system would lose information which would decrease its entropy etc.