CANCELLED-String Axiverse

Who:  Asimina Arvanitaki - (University of California, Berkeley)
Where:  1080 PRB, Robert Smith Seminar Room
When:  Tuesday, November 3, 2009 at 04:00
Type:  Colloquium

Description: String theory is the leading candidate for a theory unifying quantum mechanics with gravity. It predicts the existence of new dimensions, normally too small to be directly observed. Nevertheless, we recently discovered that the complex topology of the extra dimensions can give rise to a plenitude of new very light spinless particles, the so called "axions". Their discovery would be evidence for string theory, as their existence would be ad hoc in any theory with just the four ordinary dimensions. Their Compton wavelength can easily vary from the size of our Universe to subnuclear scales, and their signatures can appear in a wide range of astrophysical experiments. The axions can affect the polarization of the Cosmic Microwave Background at a level within reach of the Planck satellite, as well as the way matter is distributed in our universe. Interestingly, observations of rotating black holes can also probe axions through the Penrose superradiance process. When the axion size is close to the size of the black hole, it can get bound to the black hole forming a gravitational atom in the sky. The number of axions bound to that atom grows exponentially extracting angular momentum and energy from the black hole, causing the black hole to spin down, and emit gravity waves or photons that can be detected in upcoming experiments.

Additional Notes: Faculty Host: Stuart Raby