A statistical formalism of Causal Dynamical Triangulations

Recently, I and Fotini Markopoulou rewrote the Causal Dynamical Triangulations model as a spin system and provided a new method of solution of the model. The model was studies before this by Ambjorn (Niels Bohr Institute), Anagnostopoulos (Univ. of Crete) and Loll(Institute for Theoretical Physics, Utrecht University). They invented this path integral approach toward 2d quantum gravity and applied the generating functional method in their solution. (Refrence)

In addition, they have extended the model to higher dimensions (refrence) and coupled it to matter (refrence). It is interesting that a 4 dimensional spacetime is emereged by gluing 4 simplices in a specific way.

Now one can have enough fun with the new approach to the solution of the 2 dimensional model, RG transform its couplings easliy and predict the value of cosmological constant!

These models are based on the notion of the existence of a pre-assumed time in the universe and construction is led into that direction, otherwise the dimensionality of the global spacetime grows fast to infinity.
(The paper - more pictures)

Meeting on non-perturbative background independent Quantum Gravity

Here is the official webpage of this year's meeting on non-perturbative background independent Quantum Gravity, which takes place from 10-14 October 2005 at the Albert-Einstein-Institute in Potsdam, Germany.

Sean Carroll's lectures

Sean Carroll, the author of the book of Spacetime and Geometry, is giving a series of lectures in CERN about cosmology for particle physicists. The video of these talks are available a few hours after each in here. More information about this lecture.

Self-organized criticality in quantum gravity

Recentely I and Lee Smoin studied a simple model of spin network evolution motivated by the hypothesis that the emergence of classical space-time from a discrete microscopic dynamics may be a self-organized critical process. Self organized critical systems are statistical systems that naturally evolve without fine tuning to critical states in which correlation functions are scale invariant. We study several rules for evolution of frozen spin networks in which the spins labelling the edges evolve on a fixed graph. We find evidence for a set of rules which behaves analogously to sand pile models in which a critical state emerges without fine tuning, in which some correlation functions become scale invariant.