Wednesday, August 26, 2009

Loop Quantum Gravity

I attended a lecture today by Professor Abhay Ashtekar (of the Institute for Gravitation at Penn State University) about Loop Quantum Gravity at Georgia Tech. Apparently recent work has made considerable progress towards solving the infrared problem (i.e., proving agreement of LQG with classical General Relativity at low densities). Also, a density cutoff (of approximately 41% of the Planck density) has appeared naturally out of the formalism, instead of being imposed arbitrarily as an additional condition.

Slides covering material very similar to his Georgia Tech lecture can be found at
http://universe2009.obspm.fr/fichiers/Recherche/Friday-3/ashtekar.pdf

Possible ramifications of this work:
1) Help resolve the well-known horizon problem
2) Provide a mechanism for propagation of "seeds" for creating structure in the universe
3) Predicts a period of super-inflation, which could have implications for gravitational waves
4) Cause quantum corrections to the cosmic microwave backround radiation

#3 and #4 might provide testable predictions unlike superstring theory

Saturday, August 01, 2009