A string theorist reports on the Planck Scale conference

[marcus]

Jose Figueroa is in the Math Physics group at Edinburgh and his research centers on string and susy:
http://www.maths.ed.ac.uk/~jmf/
There was a big conference in Poland just now (ending today 3 July) which was interesting partly because it was mixed. Stringers gave talks alongside nonstring QG folks. It was a weeklong conference on the Planck Scale. Jose Figueroa is not only a mathematical physicist, he is also a blogger. And he blogged it:
http://empg.maths.ed.ac.uk/blog/?p=503
"I recently returned from Wrocław (a.k.a. Breslau) where I attended the first three days of the XXV Max Born Symposium: the Planck scale..."

I would say he has some blind spots but that from a certain perspective his comments are insightful and interesting.

I posted a partial speakers list for the Planck Scale conference back in April, in the Introduction to LQG thread:
https://www.physicsforums.com/showthread.php?p=2154099#post2154099
Here is the complete list:
http://www.ift.uni.wroc.pl/~planckscale/index.html?page=timetable
It seemed significant that another string theorist, Robert Helling, chose to go and deliver a paper at the Planck Scale conference in Poland rather than attend Strings 2009 in Rome. Mixed or non-exclusionary has become fashionable.
I commented on the broader trend and mentioned some other mixed conferences here:
https://www.physicsforums.com/showthread.php?p=2195225#post2195225

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That said by way of introduction, what physics intelligence might we glean by a careful reading of Figueroa's report?

 

[marcus]

One provocative part of Figueroa's report was on the talk by Hermann Nicolai, which discussed the grand desert hypothesis. Nicolai is a top German string theorist and director of the string and LQG division at AEI-Golm (a part of the Max Planck Institute system devoted to unified theories and quantum gravity). Here is a brief summary:

"Hermann Nicolai’s talk... tried to look on the bright side of the 'grand desert hypothesis'. This hypothesis says that there are no new scales between the weak unification scale and the Planck scale, so no supersymmetry, no GUTs, no large extra dimensions. This has been described as the worst case scenario of the LHC (though not presumably worse than the LHC not working at all!) but Hermann puts a positive spin on it, saying that it gives an unobstructed view to the Planck scale. His proposal, based on ongoing work with Krzysztof Meissner, is that one should depart from a classically conformally invariant minimal extension to the Standard Model and generate the masses via a conformal anomaly as in the dimensional transmutation mechanism of Coleman and Weinberg. Among the (falsifiable) predictions, there is one which puts the lightest Higgs at about 240 GeV, if I remember correctly. Good luck with that."

I'd appreciate if anyone offers comment on that. Nicolai is my model Euro string theorist--I've been watching him since 2003 when he organized a "Strings Meets Loops" conference with Ashtekar at AEI-Golm. I'd like to understand where his thought is going because I think he is unusually clear-sighted for someone in his line of research. Kris Meissner, if I remember, was co-organizer of the conference, with Kowalski-Glikman.
http://arxiv.org/find/grp_physics/1/au:+Meissner_K/0/1/0/all/0/1

There is a lot here to think about. Many of the talks correspond to papers already online at arxiv so we know roughly what some of them were about. And Figueroa indicates that video of the lectures themselves may sometime be online as well:

"There were talks on causal dynamical triangulation, noncommutative geometry à la Connes, noncommutative geometry à la Moyal, noncommutative field theory, 2-things, spin foam models, loop quantum gravity, three-dimensional gravities (quantum, topological, massive), AdS/CFT and others harder to categorise. The link above contains information on the talks and hopefully eventually also the talks themselves, as we were being filmed by what seemed to be more than one camera."

This conference, if the lectures go online, could turn out to be a goldmine of information about the current research activity in various fields.

 

[marcus]

For me probably the most interesting physics out of the whole 50 talks of the conference would be what Steve Carlip had to say:
S. Carlip Spontaneous Dimensional Reduction in Short-Distance Quantum Gravity?

Note the question mark. Carlip is campless (his research includes both string and straight QG) and people look to him as a recognized authority who writes cited review papers. Carlip is reliably sober and skeptical about stuff---fad-averse. So what he says about this is apt to be good-for-you, healthy medicine. I don't necessarily like him but I want to know what he says and I'll search for anything by him on this topic in the arxiv, and hope for the video of this talk.

Note also that Figueroa reported on Carlip's talk. Devoted more than usual blog-space to it. He would.

What he is talking about is the curious fact that in several background independent approaches to QG---background independent in the sense that LQG people use the term, i.e. not using a fixed predetermined spacetime geometric background, letting the geometry determine itself as it does in classic Gen Rel---in several of these backgroundless formulations a gradual decline in dimensionality is predicted, from 4D down to 2D, as the scale shrinks.

As you zoom in you see continuously lower and lower dimensionality. This is bizarre and the curious thing is it comes up in several very different approaches. There are papers about this by Loll, Reuter, Horava, Modesto, Benedetti (all five from different approaches)
Could it be that the space, or more exactly the geometry, we live in is actually like that?

 

[MTd2]

Recently, since last year, some E8 susy GUT models have been appearing as a way to find the SM in string theory, whose particles approaches closely the properties of the usual SM. Before that, SM was only sporadicaly hinted as subgroups of symmetries of certain compactifications that shared the same group symmetry of the standard model, but without providing a suitable lagrangian. Some of these models crowd with particles all the desert until 10^16 GEV. It's a really bold bet... Nicolai should had talked about that, but didn't...

BTW, I can imagine someone from Czech Republic calling Nicolai a crackpot. :D

 

[marcus]

Another string blogger has reported on the Planck Scale conference at Wroclaw (sometimes pronounced Breslau). This time it is Robert Helling:
http://atdotde.blogspot.com/2009/07/wrocaw-summar.html

He also discusses Hermann Nicolai's talk.