# Leap in the dark by Leonardo Modesto

1. Jan 26, 2007

### marcus

I admire the audacity of Leonardo Modesto, who has made a daring leap in the dark.

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http://arxiv.org/abs/hep-th/0701239
Loop quantum gravity and black hole singularity
Leonardo Modesto
17 pages, 7 figures. Proceedings of the XVII SIGRAV Conference, Turin, September 4-7, 2006

"In this paper we summarize loop quantum gravity (LQG) and we show how ideas developed in LQG can solve the black hole singularity problem when applied to a minisuperspace model."

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What do you think of the final paragraph of the conclusion section of this paper? He has written it in italics for emphasis.

It is interesting to recall that beyond the classical singularity the eigenvalue $\mu_E$
is negative and so we can suggest a new universe was born from the black hole formation process. In LQBH scenario pure states which fall into black hole emerge in a new universe as pure states and the information loss problem is avoided. Information is not lost in the black hole but it exists again in the space-time region in the future of the avoided singularity.

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Perhaps I should not joke and call this a "leap in the dark". He has a lot of analysis in this paper to back it up----and also he has written several earlier papers on the Loop Quantum Black Hole (LQBH).

2. Jan 26, 2007

### marcus

the curious thing is that several other people have been studying black hole in the context of background independent (non-string) QG, and have shown how the usual singularities are removed---and evolution continues nicely through what once was a singularity.

Some of these experts were invited to the SantaBarbara institute to talk about the QG removal of spacetime singularities, during the past couple of weeks, and we can download movies of their talks
But they mostly avoided discussing that time might fork. Too many puzzles and paradoxes seem to tie in here, so everybody treats the possibility with extreme caution, everybody except Modesto

Ashtekar
http://online.kitp.ucsb.edu/online/singular_m07/ashtekar/

Thiemann (first hour)
http://online.kitp.ucsb.edu/online/singular_m07/thiemann/

Thiemann (second hour)
http://online.kitp.ucsb.edu/online/singular_m07/thiemann1/

Bojowald
http://online.kitp.ucsb.edu/online/singular_m07/bojowald/

And there is also the second half of this hour discussion where Ted Jacobson was at the blackboard
http://online.kitp.ucsb.edu/online/singular_m07/babybh/

that is where Shenker prods him to reveal his basic hunch and TJ says "complementarity? forget it!" ----there is a timelike direction there so evolution continues thru the classical singularity, to what?, to something we don't know. In other words TJ put the courage of common-sense up against the mumbo-hawking-jumbo and mysteries of unitarity and entropy and no-info-loss (a kind of water-tightness with information being water) and antiSitter complementarity----mathematical superstitions that people have become deeply convinced of.

Shenker kept saying "look dere are degrees of freeeeedom down dere!", namely in the new fork of universe, so he was pushing TJ to deny the BekenHawk bound on the entropy----daring him to say there were more MICROSTATES than are supposed to be.

But all those microstates are in the FUTURE . They are not accessible because they didnt happen yet. So they don't contribute to the event horizon entropy. They are not "lost information". People get them selves into their own quagmires.

Anyway TJ was basically saying that the idea of a new spacetime region sprouting from the black bottom only violates our superstitions.
It doesnt violate actual logical reasoning.
So the evolution of spacetimematter continues to "something we don't know"----cant say it IS a fresh tract of classical and cant say it isnt either.

Last edited: Jan 26, 2007
3. Jan 26, 2007

### rtharbaugh1

Could you explain about eigenvalue negative Mu_E and how it implies new universe inside black hole?

4. Jan 26, 2007

### marcus

It baffled me why he would say it this way, Richard. I decided it was just poor communication skills. I do not think it has anything to do with negativity, merely with non-zeroness---or nonstuckness-at-zero. He is using that Mu as a clock and the place where the classic sing'ty was is located at Mu = 0

in the paper he has this model or machine for describing the world that runs time backwards from some arbitrary positive Mu (the present) back and back till he reaches Mu=0

and then it doesnt get STUCK at Mu=0, and this is the important thing:
it keeps on going

it keeps on describing the world and chugging along as if nothing had happened. this is what he is trying to tell you when he says "Mu goes negative"

but the negativity, per se, only means that volumes get turned inside out and it is the same old spacetime as always-----the negativity doesnt change anything.

It is arbitrary, he could switch from lefthand to righthand in his conventions and call US the negative part and after falling into hole Mu would be positive and our socks would be on inside out etc. It is arbitrary what is pos and what is neg (like Benjamin Franklin and which end of batteries)

5. Jan 26, 2007

### rtharbaugh1

I think I see. The singularities miniprogram has just now concluded and the question of time did indeed seem to be the big one. Is spacetime fundamental or is it emergent from something else? Can spacetime be decomposed without going through a singularity? There was a suggestion that it can be, as shown by tachyon condensation.

I want to write up my notes so will be back sometime later.

Thanks,

Richard

6. Jan 26, 2007

### marcus

In case you want pictures of the Singularities Workshop participants, to make sure of names, here are some
http://www.kitp.ucsb.edu/directory/photos/?activity=singular_m07&all [Broken]

Last edited by a moderator: May 2, 2017
7. Jan 26, 2007

### marcus

for example there's a snapshot of Bojowald

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8. Jan 27, 2007

### Chronos

The concept of time is merely a convenient way of describing which way the arrow of entropy points, IMO. Trying to isolate it as a fundamental property of the universe is a mistake.

Last edited: Jan 27, 2007
9. Jan 27, 2007

### hellfire

Why is $\mu$ interpreted as some kind of internal time? This is also the case in the cosmological models of Bojowald that I am trying to understand. As far as I understand $\mu$ labels the eingenstates of the Hamiltonian, but it is unclear to me how time evolution follows. For example, the following claim below (45) suggest me that states labeled by $\mu$ do not follow in an evolution one after each other: