Quantizing fixes the BH singularity

[Martin]

Disappearance of Black Hole Singularity in Quantum Gravity

Authors: Leonardo Modesto

Comments: 8 pages

 

"We apply techniques recently introduced in quantum cosmology to the Schwarzschild metric inside the horizon and near the black hole singularity at r = 0. In particular, we use the quantization introduced by Husain and Winkler, which is suggested by Loop Quantum Gravity and is based on an alternative to the Schrodinger representation introduced by Halvorson. Using this quantization procedure, we show that the black hole singularity disappears and spacetime can be dynamically extended beyond the classical singularity."

 

http://arxiv.org/gr-qc/0407097

 

A singularity in Gen.Rel. is a point or region where the theory breaks down and fails to calculate (produces infinities or just nonsense).

It is common for singularities in a classical theory to be fixed by quantizing the theory-------the classical atom would immediately decay, the Bohr atom didnt.

 

for decades now it has been expected that a quantum theory of gravity (a quantization of the classical Gen.Rel.) would fix the Big Bang and Black Hole singularities-----this is what one expects quantizing to do.

 

In LQC, the Big Bang singularity was fixed by Martin Bojowald, and no longer exists----our universe had a prior contracting phase----by now a halfdozen or more other researchers have confirmed Bojowald's result.

 

bojowald is likely to have been working on resolving the BH singularity (I judge by appearances from his recent papers) and he probably will publish something about it. Doubtless Modesto's paper---tho it seems to be a scoop---is not the last word. Modesto's QG is allied with and similar to Bojowald's LQC model, but not identical.

 

In Modesto's model of quantum gravity, anyway, spacetime does extend past where the classical BH singularity used to be.

[Severian]

Why are you posting this? Are you Martin Bojowald?

[Martin]

Why are you posting this? Are you Martin Bojowald?

 

No. Do you know Bojowald? he is a nice guy. he answers email sometime.

Are you in Germany?

[Dave]

To be perfectly honest, I'm not really an expert (or even near) when it comes to knowing which theory explains what in QM. It does seem to be the case that there are a lot of these theories floating around at the moment - if you could produce a summarised list of the major ones, it'd be nice.

[Martin]

"Strings, Loops, and Others: a critical survey

of the present approaches to quantum gravity"

 

Carlo Rovelli

http://arxiv.org/gr-qc/9803024

 

This was the plenary lecture on quantum gravity given at GR15

6 years ago, just like this year at Dublin they had GR17

It is a conference they have every 3 years on relativity and gravity.

 

Pages 1-14 list the various approaches to getting a quantum theory that is either a quantization of General Relativity or which handles gravity in some other way.

 

Since 1998 the field seems to have narrowed some and

in the non-string department most of the development is in LQG and its offshoot LQC

 

(loop quantum gravity and loop quantum cosmology)

 

for an up-to-date survey of LQG, related approaches, and applications to cosmology,

see the plenary lecture given at Dublin GR17 by John Baez titled

 

"Loop Quantum Gravity, Quantum Geometry, and Spin Foams"

http://math.ucr.edu/home/baez/lectures.html#lqg

 

If you click on "postscript version" you will, in my experience, get a PDF

version if that is what you need. I dont do PS but I clicked on it anyway

and somehow it was OK and I got the Baez lecture

[Martin]

...seem to be the case that there are a lot of these theories floating around at the moment - if you could produce a summarised list of the major ones, it'd be nice.

 

for the non-string approaches to quantizing gravity, that is

essentially any background-independent approach to Quantum Gravity

the main thing to know about is Loop.

 

Instead of examining everything on Rovelli's 1998 list, I would suggest

just reading one thing if you want an introduction to QG:

 

Lee Smolin

An Invitation to Loop Quantum Gravity"

http://arxiv.org/hep-th/0408048

 

this is a 50-page survey and intro for physicists in other fields who want to switch fields and do QG research. It is being submitted to Reviews of Modern Physics (a standard physics library reference for grad students looking for areas of research for dissertation).

Sound like it might be too technical? Have a look. It is surprisingly accessible reading.

 

LQG is the context in which the cosmological singularity has been removed and inflation shown to occur generically---and where the quantum operators measuring areas and volumes have discrete spectrum----Smolin lists some major results.

 

My impression is different from yours---you see a lot of non-string approaches to QG "floating around" and i see one main approach making fairly steady progress. so would advise looking at that one first

[Severian]

No. Do you know Bojowald? he is a nice guy. he answers email sometime.

Are you in Germany?

 

No (to both questions). I was just wondering.....

[Martin]

Too bad, I was hoping

Bojowald has made important contributions to quantizing relativity and especially quantizing cosmology

he got rid of the big bang singularity in 2001 and that began a line of research that includes now a growing number of people in quite a few countries

 

there are some popular science journalism accounts of his work---and related work---if you want links

[Severian]

This is quite sufficient thanks!