Loops 05 Programme

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john baez
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towards a spin foam model of quantum gravity

Hi -

You can see the transparencies of my talk at Loops '05 here:

Towards a Spin Foam Model of Quantum Gravity

I've changed the title from what appears in http://loops05.aei.mpg.de/" [Broken]. I've also changed my abstract. Here it is:


Spin foam models include several different classes of physical theories: lattice gauge theories, dynamical triangulation models of quantum gravity, "chain mail" quantum field theories, and topological string theories. Is there a spin foam model of quantum gravity in 4 dimensions? To address this question, we review recent work on causal dynamical triangulations and the renormalization group. This suggests that quantum gravity is a well-defined theory with the curious property that spacetime is effectively 4-dimensional at large distance scales, but 2-dimensional at very short distance scales. This is just what one might expect from a spin foam model, since spacetime is fundamentally 2-dimensional in these theories. We discuss properties a spin foam model should have in order to approximate general relativity at large distance scales.

I refer to a bunch of papers in my talk, but you can more easily get to those papers "[URL [Broken] my webpage[/URL].

My grad students Jeffrey Morton, Derek Wise and I are flying to Berlin this Saturday... this is gonna be fun!
 
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marcus
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john baez said:
Hi -

You can see the transparencies of my talk at Loops '05 here:

Towards a Spin Foam Model of Quantum Gravity

I've changed the title from what appears in http://loops05.aei.mpg.de/" [Broken]. I've also changed my abstract. Here it is:


Spin foam models include several different classes of physical theories: lattice gauge theories, dynamical triangulation models of quantum gravity, "chain mail" quantum field theories, and topological string theories. Is there a spin foam model of quantum gravity in 4 dimensions? To address this question, we review recent work on causal dynamical triangulations and the renormalization group. This suggests that quantum gravity is a well-defined theory with the curious property that spacetime is effectively 4-dimensional at large distance scales, but 2-dimensional at very short distance scales. This is just what one might expect from a spin foam model, since spacetime is fundamentally 2-dimensional in these theories. We discuss properties a spin foam model should have in order to approximate general relativity at large distance scales.

I refer to a bunch of papers in my talk, but you can more easily get to those papers "[URL [Broken] my webpage[/URL].

My grad students Jeffrey Morton, Derek Wise and I are flying to Berlin this Saturday... this is gonna be fun!
thanks for keeping us posted!

be sure to ship us all the tidbits you can. it is an historical conference, and we crave news of it
 
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marcus
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john baez said:
... we review recent work on causal dynamical triangulations and the renormalization group. This suggests that quantum gravity is a well-defined theory with the curious property that spacetime is effectively 4-dimensional at large distance scales, but 2-dimensional at very short distance scales. This is just what one might expect from a spin foam model, since spacetime is fundamentally 2-dimensional in these theories....
you really have redirected! now it looks like focusing on work of Loll and Reuter and aligning spinfoam so it takes in CDT as a special case
my head is reeling slightly but it was not altogether unexpected
Bravo!
you will all have a great time for sure!
 
marcus
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I have started on your lecture notes
they get hard around page 13
and interesting too

I hope other people here at PF study your notes and we can make a collective effort of understanding


I see that Tullio Regge is the hero of your pages 16, 17, 18
here's a picture
http://www.cicap.org/enciclop/at101249.htm

he's one of my heroes too. Tully (also the English nickname of Cicero)
http://plagiarist.com/poetry/3381/ [Broken] Yeats said about the other Tully

Horace there by Homer stands,
Plato stands below,
And here is Tully's open page.
How many years ago
Were you and I unlettered lads
Mad as the mist and snow?
 
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marcus
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darn it, Berislav
you should be going to Potsdam next week!

but I guess you are busy beginning university studies,
how do you like the university?
 
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marcus said:
I
I see that Tullio Regge is the hero of your pages 16, 17, 18
here's a picture
http://www.cicap.org/enciclop/at101249.htm

he's one of my heroes too. Tully (also the English nickname of Cicero)
http://plagiarist.com/poetry/3381/ [Broken] Yeats said about the other Tully

Horace there by Homer stands,
Plato stands below,
And here is Tully's open page.
How many years ago
Were you and I unlettered lads
Mad as the mist and snow?
And also Browning's "Tully's every word" from his "The Bishop Orders his Tomb at St. Praxed's Church in Rome"
http://eir.library.utoronto.ca/rpo/display/poem265.html [Broken]
 
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selfAdjoint
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Marcus said:
have started on your lecture notes
they get hard around page 13
and interesting too

I hope other people here at PF study your notes and we can make a collective effort of understanding
Which lecture notes are you reading? Can you give the link?
 
marcus
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selfAdjoint said:
Which lecture notes are you reading? Can you give the link?
JB calls it a set of transparencies but I called it notes, it reads somewhat coherently, like 18 pages of lecture notes

it is here
http://math.ucr.edu/home/baez/loops05/
and you click on "Towards a..."

and IIRC you get this pdf

http://math.ucr.edu/home/baez/loops05/loops05.pdf

In fact you may already have been looking at this (which he calls his slides) and were confused by my calling it "lecture notes"

I didnt know that poem of Browning. It's good.

BTW won't you take a look at this site. some of the best translations into English that there are on the web I think:

http://www.brindin.com/main.htm

the site has over a dozen excellent translators working on the greatest poetry in over a dozen languages----often preserving some of the music (the rhyme, rhythm, general sound) of the original

the editors are an English couple, both verse translators themselves. the English seem to be more in touch with the European verse tradition than we are---maybe it is oldfashioned education. this site really deserves to be widely known

if you find some of the good stuff you will know what i mean
================
EDIT: I went to History and made a thread about it
https://www.physicsforums.com/showthread.php?p=777322#post777322

getting close to voices from the past is a way to approach the past
 
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Kea
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marcus said:
JB calls it a set of transparencies but I called it notes, it reads somewhat coherently...
Hey guys, the references in JB's slides greatly expand the 18 pages.

:smile:
 
marcus
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Kea said:
Hey guys, the references in JB's slides greatly expand the 18 pages.

:smile:
Indeed they do!
:smile:
 
john baez
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marcus said:
I have started on your lecture notes
they get hard around page 13
and interesting too

I hope other people here at PF study your notes and we can make a collective effort of understanding.
If you have questions, ask them here and I'll try to reply! - probably after I get back from Berlin, though, unless I have time during the conference.

I see that Tullio Regge is the hero of your pages 16, 17, 18.
Yes! Actions speak louder than words, and his is one of the best.
 
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john baez said:
Hi -

You can see the transparencies of my talk at Loops '05 here:

Towards a Spin Foam Model of Quantum Gravity

I've changed the title from what appears in http://loops05.aei.mpg.de/" [Broken]. I've also changed my abstract. Here it is:


Spin foam models include several different classes of physical theories: lattice gauge theories, dynamical triangulation models of quantum gravity, "chain mail" quantum field theories, and topological string theories. Is there a spin foam model of quantum gravity in 4 dimensions? To address this question, we review recent work on causal dynamical triangulations and the renormalization group. This suggests that quantum gravity is a well-defined theory with the curious property that spacetime is effectively 4-dimensional at large distance scales, but 2-dimensional at very short distance scales. This is just what one might expect from a spin foam model, since spacetime is fundamentally 2-dimensional in these theories. We discuss properties a spin foam model should have in order to approximate general relativity at large distance scales.

I refer to a bunch of papers in my talk, but you can more easily get to those papers "[URL [Broken] my webpage[/URL].

My grad students Jeffrey Morton, Derek Wise and I are flying to Berlin this Saturday... this is gonna be fun!
This was just posted to Xr :http://arxiv.org/abs/gr-qc/0510033

prior to their leaving U.S of A.

and this may be of interest as a historical reference?:http://groups.google.com/group/sci.physics.research/browse_frm/thread/6d8038e9fd92cf2/efe70e642e41021f?hl=en&lr=&ie=UTF-8&rnum=1&prev=/groups?hl=en&lr=&ie=ISO-8859-1&q=Lattice+Gauge+Theory&btnG=Google+Search&meta=group%3Dsci.physics.research#efe70e642e41021f
 
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