The assumption that gravity in 4D couldn't be treated as a quantum field theory (any attempt would always be overrun by infinities) is being challenged.(adsbygoogle = window.adsbygoogle || []).push({});

Here is the program for a 14-16 April workshop at Bad Honnef

http://quantumgravity.aei.mpg.de/program

See the paper by Kellogg Stelle

K. Stelle:Finiteness (or not) of N=8 supergravity

http://quantumgravity.aei.mpg.de/program/Stelle..pdf [Broken]

Here's a quote from Stelle's conclusions page 27 of the PDF slide lecture notes.

"...or a series of truly miraculous D=4 cancelations to all

orders? The question remains unresolved, but according to

an old physics tradition, bets have been taken, for bottles

of wine."

Incidentally a bottle of "Stag's Leap" Cabernet Sauvignon is bet against a distinguished Rhineland white called "Diel de Diel".

================

In Kellogg Stelle's talk, the hints seem to point to the case of eightfoldsupersymmetric gravity in 4D. Things seem most hopeful in ordinary 4D spacetime, as one might expect, but using so-calledN=8 SUPERGRAVITY, where the graviton has "gravitino" partners.

================

The Bad Honnef workshop had an interesting list of about a dozen speakers including a mix of String and LQG/Spinfoam. Among the non-string folks were:

A. Ashtekar: Loop quantum cosmology: a status report

L. Freidel: Status of spin foam models

M. Reuter: Asymptotically safe quantum gravity

T. Thiemann: Loop quantum gravity

These four represented about 1/3 of the total workshop lineup.

I'd say there seems to have been a decline in camp mentality. String and non-string QG people are interested in talking to and listening to each other. Maybe this was always more the case among European physicists.

=================

Kelly Stelle discussed other N-fold supergravity, for N not equal 8. And he discussed D not equal 4. But the results seemed to point especailly to the D=4 and N=8 case.

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MORE ABOUT THIS IN A CURRENT PARIS WORKSHOP 23-28 June

http://ipht.cea.fr/Images/Pisp/pvanhove/Paris08/index.html

"Wonders of Gauge theory and Supergravity"

In particular see the talk by Zvi Bern

http://ipht.cea.fr/Images/Pisp/pvanhove/Paris08/talk_PDF/bern.pdf

Thanks to Peter Woit for calling attention to this. Here is his discussion of it:

http://www.math.columbia.edu/~woit/wordpress/?p=705

Bern's talk is titled

Ultraviolet Properties of N = 8 Supergravity at Three Loops and Beyond

the main "UV property" at issue here is convergence or finiteness. Bern's June talk is close to Stelle's April talk in subject matter.

Stelle was also at the Paris workshop. His paper is here

http://ipht.cea.fr/Images/Pisp/pvanhove/Paris08/talk_PDF/stelle.pdf

Judging by the slide lecture notes, the Paris talk is almost the same as the earlier Bad Honnef. 30 pages instead of 27. Similar conclusion on page 30 that I quoted before. But a new bet! It seems that Stelle is still betting Stag's Leap, but now he has a different opponent, who instead of betting a Rhineland white is betting a bottle of Aloxe-Corton burgundy (Domaine Chevalier).

Same talk, different wine.

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# Hints gravity finite (two recent workshops)

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