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I was browsing through this and was wondering what progress in quantum gravity research has taken place since the (preprint) publication.

If anyone can provide some helpful feedback I would be greatly appreciative.

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An update in 2004 <br/> It came up quite easily in this search. –  user2307487 Apr 24 '13 at 11:12
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@UGPhysics, You have to be specific. There are different research groups doing different research in different areas to address same topic- quantum gravity: String Theory, Quantum Loop Gravity being major. They have meetings, briefings on progress and so on. "The State" if research is definitely different from 2001 when focus was mainly on String Theory which has sifted towards LQG. But, I am not an expert, not even a physics major. –  user16682 Apr 24 '13 at 11:21
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@Dinesh The Carlip paper is quite nice because it gives a overview over most of the popular topics. Maybe he should ask for a similar but more up-to-date review paper... –  ungerade Apr 24 '13 at 14:24
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I don't know whether you can call this progress, but the AMPS paper shows that there are significant problems with the "complementarity" idea for resolving the black hole information paradox (which Carlip's paper calls "not very convincing," along with the rest of the ideas for a resolution). –  Peter Shor Apr 24 '13 at 15:04
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@user2307487: The Ashtekar paper is available on arxiv without a paywall: arxiv.org/abs/grqc/0404018 . It's only about LQG. –  Ben Crowell Apr 25 '13 at 0:55
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3 Answers 3

A few developments since 2001:

There is the new field of loop quantum cosmology, which shows some promising signs of being able to actually calculate things that might conceivably be testable by observation.

The LHC hasn't found any evidence of supersymmetry, which may reduce the appeal of string theory.

There have been some high-precision tests of dispersion of the vacuum: http://arxiv.org/abs/0908.1832 . The results have been negative. This was at one time though to be a potential test of LQG, but now it looks like LQG doesn't yet make any definite prediction.

LQG has been reformulated in the last 10 years, so if you're going to try to learn it, you want to learn it from more recent references. A presentation of the new LQG is given in Rovelli, 2011, "Zakopane lectures on loop gravity," http://arxiv.org/abs/1102.3660 .

In 2004 there was an internet debate between Smolin and Susskind on Smolin's claim that "the Anthropic Principle ... cannot yield any falsifiable predictions, and therefore cannot be a part of science:" http://www.edge.org/3rd_culture/smolin_susskind04/smolin_susskind.html

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what references do you recommend about the recent reformulation? –  lurscher Apr 29 '13 at 10:04
    
@lurscher: Added a link to a review paper by Rovelli. –  Ben Crowell Apr 29 '13 at 12:36
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Does the recent reformulation of LQG respect Lorentz invariance? –  anna v Jul 30 '13 at 4:10
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Although; this question's phraseing it's comments and its answers are a bit biased towards LQG (and and friends), the question does not explicitly prohibit string theory.

If you read Lubos Motl's TRF,,, you'd known that Since the advent of M(Atrix) theory and Matrix string theory (c.f. this, this, this, this this, and this), there has been an outburst in a field called String Phenenmenology.

For example, Bobby Acharya, Gordon Kane, and Piyush Kumar predicted that realistic M(Atrix) - theory vacua give rise to a Higgs mass of 125 GeV/c02 because of relation to the MSSM. in 2011. And it was waaaaaa...aaay before the LHC found the Higgs, so that experimental observation did not have any effect on that (see the comments. It was predicted by the MSSM, which Acharya, Kumar, Kane showed that realistic string vacua predict ). . Instead, it is a GREAT evidence for string theory. Also, note that the Higgs mass did not agree with the Standard Model, only the MSSM, and thus realistic M(atrix) theory vacua.

There have also been outbursts in string cosmology.

The Comments are valuable here, so I'll plonck them in the post just in case they get deleted . . .

1 Vote -1 it's misleading to claim that experimental observation did not have an effect on the paper. there was already 3 sigma evidence for a higgs boson at 125 GeV in December 2013. – luksen ↵ 19 hours ago

1 Vote @luksen: This paper was in April 2012 (and it was a followup, if I recall corectly, from a paper with the same result,, in 2011). The reasoning for your downvote, and your statements, is thus, completely flawed . – Dimension10 ↵ 19 hours ago the journal says: "Received: 13 April 2012" and arXiv says: "Submitted on 12 Apr 2012" – luksen ↵ 19 hours ago

1 Vote @luksen: And isn't that before 2013? – Dimension10 ↵ 19 hours ago sorry my initial comment should have said 2011. – luksen ↵ 19 hours ago

1 Vote @luksen: (1) I talked about the 2013 result. (2) If you're talking about the sudden media rage about having found a Higgs and then that died out, then, if I'm not wrong, that's generally dismissed as fluke . – Dimension10 ↵ 19 hours ago

1 Vote you're mistaken. In December 2011 both ATLAS and CMS had independently strong evidence for a Higgs at 125 GeV. Rumors of this have been floating around before the official announcement: cds.cern.ch/record/1406042 (e.g. minute 40) – luksen ↵ 18 hours ago

1 Vote Have a look at this post in December 2011 Higgs: 125 GeV Higgs rumors were accurate I think it's comical this idea that Kane et al "prdicted" the correct mass beforehand. – Larry Harson ↵ 14 hours ago

@luksen: Larry Harson linked to Lubos Motl's blog post, and it seems you're right, so I edited my post . – Dimension10 ↵ 9 hours ago @LarryHarson: Ok, guess you're right. I fixed it . – Dimension10 ↵ 9 hours ago

3 Vote The first Kane et al. paper on the Higgs mass was arxiv.org/abs/arXiv:1112.1059, posted on December 5, 2011, slightly before the ATLAS and CMS announcement on December 13. They had the result even earlier-- I was at Michigan on November 16, 2011, and Gordy told me their result then. At that point I hadn't heard the rumor, which doesn't mean none of them had. In any case, it's a straightforward prediction of having heavy scalars in the range they had been advocating for years, although emphasizing the larger tan beta values may have been a choice made in light of the data. – Matt Reece ↵ 9 hours ago

Thanks for this important clarification of the issue @MattReece. I hope it will help to do away with some misunderstandings and
prejudices some people hold. – Dilaton ↵ 9 hours ago

last point before this get's too excessive: the remaining window not excluded was already very narrow and first hints that the higgs
mass would be below 130 were known already in august 2011 after Lepton Photon 2013, e.g. blog.vixra.org/2011/08/29/… in any case I think it's a stretch to claim the higgs mass was predicted – luksen ↵ 1 hour ago

1 Vote Just to give some perspective on the Kane et al paper: People were saying that the Higgs mass should be less than 125-130 GeV in the MSSM, years before this, and without appealing to string theory. The arguments made by Kane et al are somewhat similar, they just work in a different part of MSSM parameter space - that's the part they motivate using M theory... – Mitchell Porter ↵ 22 mins ago Some reactions from String Pheno 2012: x-sections.blogspot.com/2012/06/string-phenomenology-day-2.html – Mitchell Porter ↵ 22 mins ago @MitchellPorter: Thanks (I had actually written that in my post, but this comment, along with Matt Reece's, clears it up.) ... – Dimension10 ↵ just now edit

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-1 it's misleading to claim that experimental observation did not have an effect on the paper. there was already 3 sigma evidence for a higgs boson at 125 GeV in December 2013. –  luksen Jul 29 '13 at 16:23
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The first Kane et al. paper on the Higgs mass was arxiv.org/abs/arXiv:1112.1059, posted on December 5, 2011, slightly before the ATLAS and CMS announcement on December 13. They had the result even earlier-- I was at Michigan on November 16, 2011, and Gordy told me their result then. At that point I hadn't heard the rumor, which doesn't mean none of them had. In any case, it's a straightforward prediction of having heavy scalars in the range they had been advocating for years, although emphasizing the larger tan beta values may have been a choice made in light of the data. –  Matt Reece Jul 30 '13 at 2:33
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last point before this get's too excessive: the remaining window not excluded was already very narrow and first hints that the higgs mass would be below 130 were known already in august 2011 after Lepton Photon 2013, e.g. blog.vixra.org/2011/08/29/… in any case I think it's a stretch to claim the higgs mass was predicted –  luksen Jul 30 '13 at 10:27
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Just to give some perspective on the Kane et al paper: People were saying that the Higgs mass should be less than 125-130 GeV in the MSSM, years before this, and without appealing to string theory. The arguments made by Kane et al are somewhat similar, they just work in a different part of MSSM parameter space - that's the part they motivate using M theory... –  Mitchell Porter Jul 30 '13 at 11:35
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Some reactions from String Pheno 2012: x-sections.blogspot.com/2012/06/string-phenomenology-day-2.html –  Mitchell Porter Jul 30 '13 at 11:35
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