title: Quantifying the BICEP2-Planck tension over gravitational waves.
abstract: The recent BICEP2 measurement of B-mode polarization in the cosmic microwave background (r = 0.2(-0.05)(+0.07)), a possible indication of primordial gravity waves, appears to be in tension with the upper limit from WMAP (r < 0.13 at 95% C.L.) and Planck (r < 0.11 at 95% C.L.). We carefully quantify the level of tension and show that it is very significant (around 0.1% unlikely) when the observed deficit of large-scale temperature power is taken into account. We show that measurements of TE and EE power spectra in the near future will discriminate between the hypotheses that this tension is either a statistical fluke or a sign of new physics. We also discuss extensions of the standard cosmological model that relieve the tension and some novel ways to constrain them.
authors.affiliation: Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada.
authors.forename: Kendrick M
authors.initials: KM
authors.lastname: Smith
authors.affiliation: Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, New Jersey 08540, USA.
authors.forename: Cora
authors.initials: C
authors.lastname: Dvorkin
authors.affiliation: Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada.
authors.forename: Latham
authors.initials: L
authors.lastname: Boyle
authors.affiliation: Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada.
authors.forename: Neil
authors.initials: N
authors.lastname: Turok
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Halpern
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
authors.forename: Gary
authors.initials: G
authors.lastname: Hinshaw
authors.affiliation: Department of Physics, Hamline University, 1536 Hewitt Avenue, Saint Paul, Minnesota 55104, USA.
authors.forename: Ben
authors.initials: B
authors.lastname: Gold