Skip navigation and go to content
Physics and Astronomy

Physics & Astronomy Colloquium

3:30 PM, Friday, October 1, 2010
Room 155, Chem-Phys Building

Dr. Holger Mueller
Department of Physics
University of California, Berkeley

Gravitational Redshift, Equivalence Principle, and Matter Waves
The gravitational redshift was the first consequence of General Relativity described by Einstein, and its measurement continues to be fundamental to our confidence in the theory. Clock comparison tests have reached an accuracy of 7 parts in 105, while matter wave tests, in which redshift anomalies modify material particles' Compton frequencies, have reached 7 parts in 109. The Standard Model Extension (SME) can be developed into a comprehensive model for violations of the Einstein Equivalence Principle which maintains conservation laws of the Standard Model. Here, we use SME to show that modern redshift experiments can bound anomalies that are presently poorly constrained and outside the reach of tests of the universality of free fall. We identify the similarities and differences between matter wave and clock comparison tests. Moreover, we propose the Geodesic Explorer, an atom interferometer performing a redshift measurement in a sounding rocket, the Space Station, or a freely flying satellite. Operation in microgravity converts the redshift measurement into a null measurement while the velocity along the gravitational potential gradient v provides a signal enhancement by v2/c2, which can be 106 times greater than in the lab. Such a test would provide bounds on post-post Newtonian effects of General Relativity that could be 1 billion times better than current laboratory bounds, and 10,000 times better than current astrophysics bounds.

Refreshments will be served in CP 179 at 3:15 PM