|Jul2-04, 08:01 AM||#18|
PF member solves black hole info paradox
Marcus is not a crank but he is an enthusiast. He likes to bring new papers to our attention, and he has enough physics and math background to read them, but perhaps not enough to be completely at home in the broader context.
Jeff believes that Loop Quantum Gravity is a phony field, which it is not, and has a hater response when that comes up. This latest thread comes up because Marcus made a rash claim in an area where Jeff is knowledgeable and Jeff used it as a club to beat him with. I agree with you about the tone of all this, and wonder why Jeff hasn't been warned by the mentors.
|Jul2-04, 09:59 AM||#19|
|Jul2-04, 10:17 AM||#20|
Hi sA and holly,
so far no one has pointed out any flaw in the GPP paper
a reference has been made to Vafa's paper in 1996 which
"counts microstates" of an extremal BH and gets the right
entropy formula. This is old news and suggestive
that a stringy approach might succeed in elucidating more
about black holes in the future: so it holds out hope.
But getting the right entropy formula (in certain restricted
cases) does not resolve the paradox of lost information that
arises when the black hole evaporates.
Some notable stringy people, susskind, maldacena and others,
have made heroic attempts to resolve the paradox. but still
all one can say is that the impressive not-quite-pertinent 1996 result holds out hope.
By contrast, the GPP paper gives a remarkably clear straightforward
argument that goes to the heart of the paradox and may in fact
It would be very valuable to have people try to find some flaw or catch
in the GPP handling of the paradox.
the papers here are short----like 3 pages----and the arguments are
in a sense fundamental. they do not depend on particular paraphernalia
like the loop formalism.
they depend on work of Wigner, and general arguments
so far, AFAIK, no one has administered a beating to anyone
I find that Gambini Porto and Pullin have resolved the paradox
(One could say "But that's impossible! they aren't string theorists! Nothing but string theory, which has excellent hopes, could resolve such an
important paradox!" but that wouldnt speak to the substance.)
I have stated that it appears to me they have resolved it
and there has been some clamor.
But no flaw has been found in the paper.
I would be pleased if some objective-minded people around here would have a look at it
|Jul2-04, 10:35 AM||#21|
BTW so often ad hominem arguments are used and they do distract from the real content
like maybe instead of addressing Gambini's argument one might
denigrate or belittle Gambini----or question the integrity of the messenger who leaves the paper at your doorstep
and ad hominem arguments are generally used negatively
but just for a change I would like to use a positive ad hominem argument.
I think these are smart people and I especially respect Jorge Pullin because he sits down there in Louisiana and puts out the world's best gravity newsletter----"Matters of Gravity"
this is the newsletter for real experts on quantum gravity and general relativity and gravity experiments and astronomical tests of gravity
and it is ecumenical (stringy results arent excluded if they are relevant)
and John Baez always used to keep us posted on when a new edition of the letter appeared----but he didnt last time IIRC
and for example Jorge Pullin published that prophetic essay of Matt Visser about Ambjorn and Loll's work, back in 2002,
which for a clear picture of simplex gravity and where it is going has in some sense not been improved on (unless by very recent overview comment by John Baez)
so Pullin is not just a worldclass scientist he is in a way also a journalist and editor----not for popular mass market but for colleagues in his specialty which is gravity
this is an ad hominem argument that has a bearing on this GPP paper.
it is by people who see and understand the whole picture
and are not just talking thru their hats
|Jul13-04, 01:00 PM||#22|
GPP could be right. Time-evolution could have a fundamental creeping non-unitariness which universally (not just for black holes) destroys information at the GPP rate.
this is something that Hawking appears not to have taken account of (judging from his abstract of next wednesday's talk)
If Hawking is right, in what he says on the afternoon of 21 July at the Dublin G17 conference, then Gambini et al are wrong.
Because hawking clings to an unrealistic clock.
He requires that time-evolution be unitary in terms of a ideal time-variable T that is not observed on a real physical clockface.
If that is the correct way to do quantum mechanics----using an absolute ideal Time and consequently unitary evolution (instead of the gradual adulteration calculated by GPP)----then GPP must clearly be mistaken.
But I think GPP argument is not only persuasive but also remarkably simple and direct.
I think that quantizing gravity is going to have an impact
on how quantum theory is customarily done. (this expectation is widely shared)
And I think a non-unitarian effect on the time variable is one of the first places that the impact of QG on QM is apt to be felt.
of course I am going out on a limb here! one needs to now and then. one can't know the future turns that research will take. but this is an appropriate time to hazard a guess, with Hawking's talk in the offing.
notice that Haelfix, in another thread, has made a solid point in favor of Hawking. He observes that Hawking has an impressive record of being right about black holes.
(the information paradox is not wholly an issue of black holes, it is also an issue of time---time is the joker in the deck)
|Jul13-04, 01:42 PM||#23|
I am also rather annoyed by Jeff's adversarial posts- it would be more tolerable if Jeff were not stuck in the 90s when String Theory was at odds with the new upstart LQG-
Jeff still seems to think that LQG is this new and wrong challenger to SST- but the work in Quantum Gravity during the 21st century has shown that they are two perspectives of the same theory- it's all about unification- like Lee Smolin puts it- SST appears to be the Elephantís trunk while LQG is itís tail- or ears- or intestines- or- something-
Hey Jeff- would it kill you to read a paper or listen to a lecture from THIS century- something after 1998 would do you some good!
yes Marcus is rather too excited about LQG- but his excitement is justified-
/:set\AI transmedia laboratories
|Jul13-04, 02:30 PM||#24|
|Jul13-04, 02:37 PM||#25|
When someone makes ME the issue, whoever the "me" is, I deplore and ignore the post. or HIS, whoever.
like, MY honesty
MY motives in wanting to discuss something
or HIS. that's not what it's about
setAI, you can see my viewpoint here----even if your criticisms of Jeff are constructive and your remonstrances contain good advice, it is just apt to divert the thread into a discussion of people
Jeff will be apt to say that HE is all for unification but that it is MARCUS who was critical of string theory, and so on and so on.
I just have to tune that kind of discussion out.
I really want to focus on this time issue.
You could say the debate here (Hawking versus Gambini et al) is among the non-stringy approaches to quantizing gravity. String has no bearing on it besides the fact that Susskind and Maldacena made mighty efforts to resolve the paradox in the 1990s but that is history.
The current thing is between Hawking (who has his own non-string bid to QG) and Gambini et al (whose argument is so general it doesn't depend on some specific approach such as Loop!)
This is another cool thing about the GPP paper, it works on very general arugments----so it is not dependent on some specific thing like LQG or spin foam or Simplex or whatever. they just need a discrete area spectrum (which you do get in various versions of Loop but which is widely expected to result in any successful quantization of spacetime geometry)
gravity = geometry and quantizing geometry means quantizing area
so in whatever theory area is going to have a discrete bunch of eigevalues, like the energy levels of an atom---everybody expects this of QG---and that is about all they need for their argument
am I excited by this, you bet! Gambini et al are saying something really new about time
and what they are saying about time is a pitfall in Hawking's path
time will tell
|Jul16-04, 04:55 AM||#26|
Jeff, just curious, what is your background in science, do you work in quantum gravity?
AFAIK, there is no 'majority' view on String theory, LQG etc etc. Most people work in their respective field, and don't know much about the other, so are not in a great position to give much of a comment either way.
I can safely say that in terms of astrophysicists and particle physicists who work at medium energy scales, that I know and have worked for, they are all equally as skeptical of pretty much every attempt to account for gravity in a quantum context.
What we tend to hear from the Stringy people is 'well theres lots of hope here', and everyonce and awhile we'll see a cool and rather deep unity with guage theory. But then again, we hear a lot of the same stuff from LQG.
I can safely say though, that there are very few cranks in either field. People like Ashtekar and Witten are not like the Bogdanov twins, and I find it hard to believe either would be pushing completely vacuous theories.
|Jul16-04, 10:56 AM||#27|
Keeping in mind that the philosophy underlying lqg is that GR must be taken most seriously as a guide to what a quantum theory of gravity should look like, consider the following six questions about lqg:
1) Is lqg a background-independent theory?
2) Is lqg a discrete theory, i.e., are the spectra of it's observables discrete?
3) Is lqg a quantum theory of gravity?
4) Is lqg's low energy effective theory GR?
5) Is it plausible that lqg's treatment of the hawking-beckenstein black hole area-entropy law could be correct?
6) Does lqg remain faithful to all or even most of the inferences people feel should be drawn from GR?
7) Is lqg faithful to any of the most important lessons field theory has taught us?
|Jul19-04, 03:35 PM||#28|
- - mentor hat - -
Hang on, folks. We see what's going on here & are discussing it.
In general, being incorrect about something (hypothetically speaking) is not cause for mentor wrath. We're here to encourage a good discussion/debate. Heated discussions are not uncommon and are typically evaluated on a case-by-case basis. Sometimes we have to step in to maintain a quality forum and other times we let the members work it out. We don't want to be "Big Brother" and moderate every line of every topic. We're members too and prefer just to enjoy the discussions. Some things like flame wars, unwarranted insults, or inappropriate content are (usually) quickly caught by the mentors/advisors and addressed.
|Similar Threads for: PF member solves black hole info paradox|
|Black Hole Paradox||Special & General Relativity||4|
|Black Hole Paradox?||Special & General Relativity||0|
|S. Hawking & black hole info paradox||Beyond the Standard Model||1|
|Hawking Solves Black Hole Mystery||General Astronomy||51|