California Institute of Technology

Based largely on recent observations of the Cosmic Microwave Background (CMB), cosmologists believe that the entire observable Universe was spawned in a fraction of a second by the superluminal “inflation” of a sub-atomic volume. This paradigm presents a remarkable opportunity. Inflation produced a Cosmic Gravitational-wave Background (CGB) that may be detectable now via a faint signature imprinted in the polarization of the CMB. To do so could probe the very moment at which the Universe sprang into existence and explore energies far higher than will ever be achieved in terrestrial accelerators. This project will search for the signature of the CGB due to inflation using a set of novel, microwave polarimeters sited at the South Pole. A prototype experiment now in its third year of operation at the South Pole has proven the methodology. A full set of more capable polarimeters is proposed to be built. This technique will allow a search for the CGB with sensitivity exceeding that targeted by the Task Force on CMB Research for a future orbital mission, at least a decade earlier and at ~ 1% of the cost of an orbital mission. A detection of the signature of the CGB would be an historic achievement for both cosmology and high-energy physics.