Monday, April 18, 2005

The Cosmology Report from Tampa

I’m on my way back from Tampa, blogging from the airport again. I have found this to be a very productive trip. A conference like this one, with a large number of attendees, has many talks and events. It is easy to spend the entire time rushing around from talk to talk, trying to see as many interesting topics as possible. However, I don’t get the most out of conferences that way. These days I pick and choose the talks I really need to see, plus a few at which I’d like to show support for colleagues or students. The rest of the time I spend meeting and discussing with colleagues. Sometimes these are preexisting collaborators and other times they aren't, but the conversations lead to new collaborations.

On this trip I attended a number of interesting talks; Rocky Kolb on Einstein’s Cosmic Legacy; Don Marolf on Quantum Gravity; Konstantin Matchev and Richard Schnee on Dark Matter; Rachel Bean on dark energy perturbations, to name just a few. Plus, as I mentioned in yesterday’s post, I also went to the Scientific Integrity in Government session.

I had a lot of fun in the Cosmological Constraints on Theories of Gravity and Fundamental Physics session, in which I delivered my invited talk on Theories of Cosmic Acceleration. What I enjoyed most about this session were the excellent talks by the other two invited speakers. Arthur Kosowsky (currently of Rutgers University, but soon to move to the University of Pittsburgh) gave a wonderful talk on the possibility that modifications of gravity might play a role in explaining the puzzles that one usually explains with dark matter. This idea usually goes under the name MOdified Newtonian Dynamics (MOND). First proposed by Milgrom, it invokes a change to the gravitational force law at a specific scale, altering the dynamics of galaxies and providing a stunning fit to galaxy rotation curves. This is by no means a popular idea, but it is fascinating that the fit to rotation curves is so successful. One reason that people initially did not spend much time on MOND is that, in its original incarnation, it is merely a phenomenological modification of Newtonian gravity and, as such, wouldn’t explain other observations that are explained by dark matter, such as gravitational lensing of galactic clusters. However, in the last year Jacob Bekenstein has formulated a covariant version of MOND. While his model is not exactly pretty, it has a honest-to-goodness covariant Lagrangian, and so one can, in principle, calculate all the implications of the theory, not just the rotation curves.

Hiranya Peiris from the University of Chicago then gave a tremendous talk on the Cosmic Microwave Background (CMB) radiation, describing how precision measurements of the fluctuations provide constraints on models of the early universe. Hiranya is the right person to do this, since she was the first author on the paper deriving these constraints from the WMAP data. .

Lots of fun physics packed into three busy days. Now back to Syracuse, where tomorrow it will be 77 degrees and beautifully sunny.
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