**Probing New Physics with Gravitational Waves**

Dr. Jan Schütte-Engel

UIUC

The thermal plasma in the early universe produced a guaranteed stochastic gravitational wave (GW) background, which peaks today in the microwave regime and was dubbed the cosmic gravitational microwave background (CGMB). I show that the CGMB spectrum encodes fundamental information about particle physics and gravity at ultra high energies. In particular, one can determine from the CGMB spectrum the maximum temperature of the universe and the effective degrees of freedom at the maximum temperature. Quantum gravity effects arise in the CGMB spectrum as small corrections. I argue that a detection of these effects would indicate that gravity is quantized. At the end of the talk, I discuss detection prospects of the CGMB with microwave cavities.