January 26, 2006

Dark Sector of the Universe the Henan Way

The dark sector, energy and matter, of the universe is under intensive study these days for good reasons. A proposal for the dark stuff comes from Henan, China (some 400 km to the east of Shanghai). Mian Wang sets up an alternative GR with an additional scalar field (phi). Other scenarios mentioned by Wang include cosmological constant, of course, quintessence, dilaton, axion, tachyon, phantom field, and Chaplygin gas. Like the last in the list, Wang's model offers unified description of both dark energy and matter in succeeding cosmological evolution stages, starting from the inflationary period. His action is this (it should appear in your browser).

In this model the universe is created from the instanton solution, discussed in a previous paper by the author, of field phi when the field is dropped in the left potential well for negative phi. During the period of exponential inflation lambda(phi) provides a large cosmological constant. The inflation ends dynamically when rho + 3p ~ rho_phi + 3p_phi increases from −2rho_phi to zero. A graceful exit from inflation is claimed. After inflation of the early universe the scalar field behaves like cold dark matter, and the universe expands according to 2/3 power law. It looks promising. We shall see whether these arguments will be substantiated by the cosmological community.

January 25, 2006

Light Particle in the Landscape

The holiday season is well over and papers have appeared this month in the arXiv but I have not read any well. I noticed that Lubos Motl had carefully chosen the submission moment to get the number 001 for his paper with Arkani-Hamed, Nicolis and Vafa. Sure enough, it is now the beginning of the second century of quantum physics ;-) . Some comments of the paper were written by Jacques Distler in his blog on January 20. I try to get some idea of this (next month, I guess ... after getting rid of some aches). Very briefly, the authors conjecture an upper bound on the coupling of gravity with respect to gauge forces. This implies new physics beneath the Planck scale near GUT scale with a light charged particle.

Not unexpectedly, the string discussion between Lubos and Peter Woit is flourishing after Peter was interviewed by Susan Kruglinski of Discover Magazine. There are twenty two responses at the moment on Peter's blog. Enjoy!