Marcus said:[MY COMMENT: this is "Julia sets" Julia. I didn't know to expect him to show up at a Loops conference
selfAdjoint said:Maybe we mean something different by Julia Sets? I mean the well-known classical fractal sets of that name; these were devised by Prof. Raoul Julia who fought in WWI and I don't suppose is around anymore.
Berislav said:This might sound like a silly question, but...
Is the picture on their homepage a rendering of CDT?
marcus said:it definitely is not a silly question
the "icon" chosen for a line of research can be a helpful handle on it
I think that the picture is actually a unification of two or more theories where in the FOREGROUND near the viewer I see the triangles of CDT
and FURTHER AWAY more in the background, I see loops emerging, or perhaps they are nonperturbative strings and branes, as some largerscale structures, already kind of foggy or blurred, emerge out of the primitive small scale triangles.
at least one of the pictures has this suggestive foreground-blending-into-background thing
If I were to meet hermann nicolai, I think I would ask him did he choose the artist or the pictures for this AEI website?
I think he is a clever far-seeing man and although his specialty is string, I think he WANTS THE BEST for all approaches to quantum gravity and he believes that they can work in a synergistic way to test each other and so on. a man like Nicolai could have decided on that picture.
(if anyone doesn't know: nicolai directs the Unified theories and Quantum gravity department of AEI-Potsdam where they are hosting the conference)
marcus said:the most illuminating thing I have seen since Friday when the program came out (bearing on the current QG picture) is this comment on Woit blog by JB
this post is #53 in the comments...
---quote JB on Woit blog---
But, to answer your question, what could get me working harder on quantum gravity is some evidence that we can find a mathematically elegant background-free quantum theory that can reduce to general relativity in a suitable limit. I see no reason why such a thing can’t be found if we drop the restriction on “mathematical elegance” - but I like things that use beautiful math.
This is precisely why I mentioned Carlo Rovelli’s new paper...
Spin_Network said:Marcus, one of the main things to consider is what Olaf Dreyer:http://loops05.aei.mpg.de/index_files/abstract_dreyer.html
appears to tackling?
I have one or two things I would be very interested in finding out regarding Quantum to Macro transitions, having my own ideas, I am going to see how close I am to what the Theorists predict, but I ll leave that till about two days before the programme gets under way.
Regarding the "new hypotheses" from Smolin,http://loops05.aei.mpg.de/index_files/abstract_smolin.html
I wonder what it could involve?..I have a number of calculated guesses, but,again this will go onto my website no later than two days before the start date.
Chronos said:Terno and Markopoulou are giving presentations based on quantum information theory on Monday [Markopoulouday on my calender]. I'm a big fan of QIT. FM's presentation should be quite interesting
Title: Erorr-free quantum gravity
Abstract: We investigate the possibility that a background independent quantum theory of gravity is not a theory of quantum geometry. We provide a way for global spacetime symmetries to emerge from a background independent theory without geometry. In this, we use a quantum information theoretic formulation of quantum gravity and the method of noiseless subsystems in quantum error correction. This is also a method that can extract particles from a quantum geometric theory such as a spin foam model.
Instead of the usual 'sum of geometries' approach to quantum gravity, FM is suggesting the geometry itself may be emergent. How is that for background independence? This appears to build upon a presentation from late 2004. Here's a link if anyone is interested:
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 going to be fun!
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...
I see that Tullio Regge is the hero of your pages 16, 17, 18
here's a picture
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?
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
selfAdjoint said:Which lecture notes are you reading? Can you give the link?
marcus said:JB calls it a set of transparencies but I called it notes, it reads somewhat coherently...
Kea said:Hey guys, the references in JB's slides greatly expand the 18 pages.