Limits on dark radiation, early dark energy, and relativistic degrees of freedom

Erminia Calabrese, Dragan Huterer, Eric V. Linder, Alessandro Melchiorri, and Luca Pagano Physics Department and INFN, Universita’ di Roma ‘‘La Sapienza’’, Ple Aldo Moro 2, 00185, Rome, Italy Department of Physics, University of Michigan, 450 Church St, Ann Arbor, Michigan 48109, USA Berkeley Lab & University of California, Berkeley, California 94720, USA. Institute for the Early Universe WCU, Ewha Womans University, Seoul, Korea Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena California 91109, USA (Received 30 March 2011; published 2 June 2011)