Quantum Gravity = Quantum Relativity is heating up

[Martin]

Looking for a quite place to put some thoughts and links about what's happening in the ongoing struggle to quantize relativity.

As everybody knows, the prevailing theory of gravity

is a geometrical theory called General Relativity

where gravity is modeled by geometry.

 

Gen Rel came out in 1915 and has been repeatedly tested since around 1919 and is doing fine. A satellite experiment to further test it, called Gravity Probe B, went up this year. Gen Rel is where ideas like bigbang, blackhole, darkenergy, cosmological constant, accelerating expansion, gravitational lensing (light bending) etc. come from.

 

To quantize Gen Rel means to quantize geometry

and, in effect, to arrive at a quantum picture of what spacetime is.

so "Quantum Gravity" means a quantum theory of space and time and how they are shaped by matter.

 

A quantum theory of gravity is just emerging---there are several approaches.

 

2004 is a banner year

 

Penrose book is about this to a substantial degree. I just checked and as of 8AM Friday 6July2004 the penrose book was #4 on Amazon.uk.co

bestseller list.

http://www.amazon.co.uk/exec/obidos/tg/stores/static/-/books/amazon-bestsellers/ref=cs_nav_sn_4/202-5121337-2949434

As of 5PM Friday it was #3, topped only by a diet book and the Da Vinci Code.

 

Also Carlo Rovelli book "Quantum Gravity" is coming out in Fall 2004 from Cambridge Uni Press. this is the first comprehensive LQG graduate-level textbook.

http://www.cpt.univ-mrs.fr/~rovelli/rovelli.html

 

Also Lee Smolin has posted "An Invitation to Loop Quantum Gravity" a 50-page survey and intro for physicists in other fields who want to switch fields and do QG research. http://arxiv.org/hep-th/0408048

Smolin's "Invitation" is being submitted to Reviews of Modern Physics.

 

Also John Baez gave a skillful up-to-date survey at the Dublin GR17 conference, which is available online at Baez site.

"Loop Quantum Gravity, Quantum Geometry and Spin Foams"

http://math.ucr.edu/home/baez/lectures.html#lqg

 

 

"Quantum Gravity Phenomenology" was the topic of the Winterschool-2004 (WS-2004) symposium this year, 4-14February, a 10-day conference on the initial and planned efforts to test QG by empirical observation.

http://ws2004.ift.uni.wroc.pl/html.html

click on lectures if you want slides from the various talks given at WS-2004

 

 

Observational tests of QG have already had a considerable impact as discussed by Smolin in the "Invitation" survey article starting page 27.

LQG is rapidly reaching a point where it can guide experiment---if one counts certain kinds of astronomical observation as experiment and I don't see why one wouldnt

 

Cambridge Uni Press is also publishing "Universe or Multiverse" which will contain a chapter by Smolin called "Scientific Alternatives to the Anthropic Principle" where he offers an evolutionary Multiverse hypothesis that generates testable (numerical) predictions and therefore has meaning as a part of science.

http://arxiv.org/hep-th/0407213

Smolin's Multi is falsifiable, in fact, using today's methods, by the ongoing search for pulsars. It predicts a cap on pulsar mass of below 2 solar (finding a pulsar of over 2 solar would refute Multi)

 

These are signs that QG is coming into its own as a research field. i will try to get some links to substantiate this and give readers a chance to find out more on their own.

[Martin]

More on the "2004 banner year" topic

 

the first Scientific American article on LQG appeared in January 2004

Lee Smolin

"Atoms of Space and Time"

It is a good article---tho not available online

 

A series of 3 articles by a German science journalist named Rudy Vaas

also appeared this year in a SciAm-like German magazine, and were

translated into English and made available online

 

Beyond Space And Time

Ruediger Vaas

7 pages, English translation of "Jenseits von Raum und Zeit"

http://arxiv.org/physics/0401128

 

The Duel: Strings versus Loops

Ruediger Vaas

10 pages, English translation of "Das Duell: Strings gegen Schleifen"

http://arxiv.org/physics/0403112

 

The Inverted Big-Bang

Ruediger Vaas

8 pages

http://arxiv.org/physics/0407071

 

--------------------

LQG has gotten noticeably more visible----visibly more noticeable?----suddenly there's a lot more attention. Also research activity has speeded up this year. I will get some numbers.

[Martin]

Here are arXiv counts for Loop and allied approaches over the past 10 years. the main thing to notice is the percentage change from year to year. the absolute numbers are not perfect since the search proceedure is not (keywords pick up some they shouldnt and leave out some). These are preprints posted each year for past 10 years. You can see there was not much change for a long while and then activity starts to shoot up.

 

 

Year 1994:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/1994/0/1

 

Year 1995:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/1995/0/1

 

Year 1996:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/1996/0/1

 

Year 1997:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/1997/0/1

 

Year 1998:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/1998/0/1

 

Year 1999:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/1999/0/1

 

Year 2000:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/2000/0/1

 

Year 2001:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/2001/0/1

 

Year 2002:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/2002/0/1

 

Year 2003:

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/2003/0/1

 

Last twelve months (e.g. 5 August 2003 to 5 August 2004):

http://lanl.arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+OR+triply+doubly+special/0/1/0/past/0/1

 

1994    59    
1995    81    
1996    69
1997    68
1998    59
1999    73
2000    83
2001    92
2002   113
2003   129
LTM    145