Cosmology Seminar Announcement Professor Justin Khoury MIT " Chameleon Scalar Fields: Detecting Dark Energy with Tests of Gravity " Date: Thursday, January 13, 2005 Time: 12:10 pm. 416 Physics Abstract: Chameleons are scalar fields whose mass depends on the local matter density: they are massive on Earth, where the density is high, but essentially free in the cosmos, where the density is low. All existing tests of gravity are satisfied. We predict that near-future satellite experiments could measure an effective Newton's constant in space different by order unity from that on Earth, as well as violations of the Equivalence Principle stronger than currently allowed by laboratory experiments. Moreover, we argue that the chameleon can naturally be the quintessence field driving the current phase of cosmic acceleration. We present a simple model of a chameleon, namely \phi4 theory, and show how it drastically alters current constraints from gravity experiments.

E-Mail: jkhoury@lns.mit.edu
Web Page: www.mit.edu