c****e
发帖数: 2097 | | w****1
发帖数: 4931 | 2 loop quantum gravity is nonsense.:))
【在 c****e 的大作中提到】
: kow tow O7|_
| c****e
发帖数: 2097 | 3 i don't happen to think that all the work starting with Bryce Dewitt and
Abhay Ashtekar are nonsenses. well, Lee Smolin et.al. tried to develop
it a bit, but not successfully. one of the problems was pointed out by
Ed Witten, which was that the Kodama state Lee proposed as the va-
cuum state was not a physical state. It had a very specific pathology,
argued Witten. But witten's argument was not really rigorous, more
heuristic. So wondering if any LQG guy is around to talk in some depth
about tha
【在 w****1 的大作中提到】
: loop quantum gravity is nonsense.:))
| w****1
发帖数: 4931 | 4 Ok I don't know these two guys. I talked to a couple some sort of "experts"
in LQG before, and I wasn't impressed.:) About Lee Smolin, I totally agree
with Lubos: his papers are child's play.
【在 c****e 的大作中提到】
: i don't happen to think that all the work starting with Bryce Dewitt and
: Abhay Ashtekar are nonsenses. well, Lee Smolin et.al. tried to develop
: it a bit, but not successfully. one of the problems was pointed out by
: Ed Witten, which was that the Kodama state Lee proposed as the va-
: cuum state was not a physical state. It had a very specific pathology,
: argued Witten. But witten's argument was not really rigorous, more
: heuristic. So wondering if any LQG guy is around to talk in some depth
: about tha
| c****e
发帖数: 2097 | 5 You don't know Bryce DeWitt? Did you not read the very first serious
papers on canonical quantization of gravity? I thought those were
the 3 papers by DeWitt :D I guess you meant not to put those 2
brighter guys with Lee Smolin.
Lubos is probably right on many things, but apparently there's 1 LQG
speaker in strings this year. I just like to use my own judgement
instead of others, however it's hard to have time to go into that
literature, as it's pretty unenlightened.
I don't want to overstate it
【在 w****1 的大作中提到】
: Ok I don't know these two guys. I talked to a couple some sort of "experts"
: in LQG before, and I wasn't impressed.:) About Lee Smolin, I totally agree
: with Lubos: his papers are child's play.
| w****1
发帖数: 4931 | 6 Oh you mean THE deWitt.:D I never knew his first name. If you only care
about solving quantum field theories by themselves, susy is a simplification
. While you can't solve the harder problems, solving easier problems is
progress. You can't say you are fed up with it unless you have better ideas.
【在 c****e 的大作中提到】
: You don't know Bryce DeWitt? Did you not read the very first serious
: papers on canonical quantization of gravity? I thought those were
: the 3 papers by DeWitt :D I guess you meant not to put those 2
: brighter guys with Lee Smolin.
: Lubos is probably right on many things, but apparently there's 1 LQG
: speaker in strings this year. I just like to use my own judgement
: instead of others, however it's hard to have time to go into that
: literature, as it's pretty unenlightened.
: I don't want to overstate it
| w****1
发帖数: 4931 | 7 It looks like we also have different opinions on what are "deep" works.
Surely it's nice to say generic things, but there are only so many generic
things one can say. Progress is often made about one particular model, and
then later generalized. Take one of my favorite old papers, non-susic,
Zamolodchikovs' exact solutions of O(N) model and sine-Gordon model. These
are very special models, but their method is general and the work is
certainly a deep one.
【在 c****e 的大作中提到】
: You don't know Bryce DeWitt? Did you not read the very first serious
: papers on canonical quantization of gravity? I thought those were
: the 3 papers by DeWitt :D I guess you meant not to put those 2
: brighter guys with Lee Smolin.
: Lubos is probably right on many things, but apparently there's 1 LQG
: speaker in strings this year. I just like to use my own judgement
: instead of others, however it's hard to have time to go into that
: literature, as it's pretty unenlightened.
: I don't want to overstate it
| c****e
发帖数: 2097 | 8 yeah, you can't claim to be fed up while still hungry :D
sometimes it won't take a saint to notice something is probably
wrong though
simplification
ideas.
【在 w****1 的大作中提到】
: Oh you mean THE deWitt.:D I never knew his first name. If you only care
: about solving quantum field theories by themselves, susy is a simplification
: . While you can't solve the harder problems, solving easier problems is
: progress. You can't say you are fed up with it unless you have better ideas.
| c****e
发帖数: 2097 | 9 ok, let me take some words back, i meant by models the ones particle
physicists like to construct these days and all look identical sort of.
personally i think work such those done by Landau are really deep.
and yeah, without some miracles, generic knowledge is equally
unpredictive. so, i still maintain that i do think discussing
QG is deeper than a lot of effective field theory discussions.
i still wanna understand some of LQG.
【在 w****1 的大作中提到】
: It looks like we also have different opinions on what are "deep" works.
: Surely it's nice to say generic things, but there are only so many generic
: things one can say. Progress is often made about one particular model, and
: then later generalized. Take one of my favorite old papers, non-susic,
: Zamolodchikovs' exact solutions of O(N) model and sine-Gordon model. These
: are very special models, but their method is general and the work is
: certainly a deep one.
| w****1
发帖数: 4931 | 10 Please, be specific when you speak of "models particle physicists like to
construct", otherwise we have nothing to discuss here.
【在 c****e 的大作中提到】
: ok, let me take some words back, i meant by models the ones particle
: physicists like to construct these days and all look identical sort of.
: personally i think work such those done by Landau are really deep.
: and yeah, without some miracles, generic knowledge is equally
: unpredictive. so, i still maintain that i do think discussing
: QG is deeper than a lot of effective field theory discussions.
: i still wanna understand some of LQG.
| | | c****e
发帖数: 2097 | 11 let's say the press release about tevraton data favoring MSSM, which
of the 124 dimensional parameter space of models are they talking about?
mSUGRA?
maybe it's very embarrassing to say clearly what they really mean.
same here, i am annoyed by the abundance of stupid models.
and people have endless resourcefulness in constructing a few
every year/month/day. well, it seems not a smart thing to do
to care about these redundant stuff, after all, life is short.
another example I don't feel particul
【在 w****1 的大作中提到】
: Please, be specific when you speak of "models particle physicists like to
: construct", otherwise we have nothing to discuss here.
| c****e
发帖数: 2097 | 12 right, i never knew witten's first name as it also seemed a rare name
outside academia. well, now i know.
btw, thanks for the discussions. and best of luck with your exploration
of further insights in ads/cft.
simplification
ideas.
【在 w****1 的大作中提到】
: Oh you mean THE deWitt.:D I never knew his first name. If you only care
: about solving quantum field theories by themselves, susy is a simplification
: . While you can't solve the harder problems, solving easier problems is
: progress. You can't say you are fed up with it unless you have better ideas.
| w****1
发帖数: 4931 | 13 That's why Nima and company are going backward now, trying to learn about
models directly from experimental data. And that is also why some string
theorists are exploring the entire landscape rather than constructing one
model after another model. We are not all stupid -- we always do the best we
can.
【在 c****e 的大作中提到】
: let's say the press release about tevraton data favoring MSSM, which
: of the 124 dimensional parameter space of models are they talking about?
: mSUGRA?
: maybe it's very embarrassing to say clearly what they really mean.
: same here, i am annoyed by the abundance of stupid models.
: and people have endless resourcefulness in constructing a few
: every year/month/day. well, it seems not a smart thing to do
: to care about these redundant stuff, after all, life is short.
: another example I don't feel particul
| c****e
发帖数: 2097 | 14 hmm, exploring the entire landscape is a high order.
we
【在 w****1 的大作中提到】
: That's why Nima and company are going backward now, trying to learn about
: models directly from experimental data. And that is also why some string
: theorists are exploring the entire landscape rather than constructing one
: model after another model. We are not all stupid -- we always do the best we
: can.
| w****1
发帖数: 4931 | 15 I find it more interesting to explore the swampland.
【在 c****e 的大作中提到】
: hmm, exploring the entire landscape is a high order.
:
: we
| c****e
发帖数: 2097 | 16 i am a bit challenged with the distinction, actually.
yeah, alligators and exotic birds are waiting.
【在 w****1 的大作中提到】
: I find it more interesting to explore the swampland.
| w****1
发帖数: 4931 | 17 To me swampland means consistent theories of quantum gravity that are not (
limits of) string theories. It's not obvious that the swampland is nonempty. | c****e
发帖数: 2097 | 18 you are not talking with the N=8 supergravity theory in mind, are you?
or the ads3 pseudo-gravity :) those two are very stringy.
whatever lies in the swampland, the study of them is very limited so
far. i would complain that's because people are too devoted to working
out variants of known results with ever smaller relevance/content.
nonempty.
【在 w****1 的大作中提到】
: To me swampland means consistent theories of quantum gravity that are not (
: limits of) string theories. It's not obvious that the swampland is nonempty.
| w****1
发帖数: 4931 | 19 I do have these in mind, among other things.:) I don't see why they are
stringy. String theories typically completes gravity in the UV by
introducing infinitely many massive fields. Whenever you have a potentially
simple UV completion of gravity, it would smell like swampland. Of course,
little is known about such theories.
【在 c****e 的大作中提到】
: you are not talking with the N=8 supergravity theory in mind, are you?
: or the ads3 pseudo-gravity :) those two are very stringy.
: whatever lies in the swampland, the study of them is very limited so
: far. i would complain that's because people are too devoted to working
: out variants of known results with ever smaller relevance/content.
:
: nonempty.
| c****e
发帖数: 2097 | 20 right, either of those could have a go. but if the N=4 SYM had a string
dual, maybe the N=8 supergravity would regain string theory status
somehow too.
so yeah, the signature of string theory is such that it does not complete
gravity in the UV by making it a renormalizable model in the usual
and 4d sense. it's actually pretty 'nasty' due to all these extra stuff.
potentially
【在 w****1 的大作中提到】
: I do have these in mind, among other things.:) I don't see why they are
: stringy. String theories typically completes gravity in the UV by
: introducing infinitely many massive fields. Whenever you have a potentially
: simple UV completion of gravity, it would smell like swampland. Of course,
: little is known about such theories.
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