Search Publications
Cosmological Constraints on Brans-Dicke Theory
Avilez, A.; Skordis, C.
We report strong cosmological constraints on the Brans-Dicke (BD) theory of gravity using cosmic microwave background data from Planck. We consider two types of models. First, the initial condition of the scalar field is fixed to give the same effective gravitational strength Geff today as the one measured on Earth, GN. In th…
Possible Evidence for Free Precession of a Strongly Magnetized Neutron Star in the Magnetar 4U 0142+61
Hiraga, J. S.; Enoto, T.; Murakami, H. +5 more
Magnetars are a special type of neutron stars, considered to have extreme dipole magnetic fields reaching ∼1011 T. The magnetar 4U 0142+61, one of the prototypes of this class, was studied in broadband x rays (0.5-70 keV) with the Suzaku observatory. In hard x rays (15-40 keV), its 8.69 sec pulsations suffered slow phase modulations by …
Evidence for Gravitational Lensing of the Cosmic Microwave Background Polarization from Cross-Correlation with the Cosmic Infrared Background
Ade, P. A. R.; Borrill, J.; Keskitalo, R. +74 more
We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical…
Inflation with Whip-Shaped Suppressed Scalar Power Spectra
Starobinsky, Alexei A.; Hazra, Dhiraj Kumar; Smoot, George F. +1 more
Motivated by the idea that inflation occurs at the grand unified theory symmetry breaking scale, in this Letter we construct a new class of large field inflaton potentials where the inflaton starts with a power law potential; after an initial period of relatively fast roll that lasts until after a few e folds inside the horizon it transits to the …
Standard Rulers, Candles, and Clocks from the Low-Redshift Universe
Verde, Licia; Jimenez, Raul; Heavens, Alan
We measure the length of the baryon acoustic oscillation (BAO) feature, and the expansion rate of the recent Universe, from low-redshift data only, almost model independently. We make only the following minimal assumptions: homogeneity and isotropy, a metric theory of gravity, a smooth expansion history, and the existence of standard candles (supe…
No New Cosmological Concordance with Massive Sterile Neutrinos
Leistedt, Boris; Peiris, Hiranya V.; Verde, Licia
It has been claimed recently that massive sterile neutrinos could bring about a new concordance between observations of the cosmic microwave background, the large-scale structure of the Universe, and local measurements of the Hubble constant, H0. We demonstrate that this apparent concordance results from combining data sets which are in…
Čerenkov Emission of Quasiparallel Whistlers by Fast Electron Phase-Space Holes during Magnetic Reconnection
Eastwood, J. P.; Andersson, L.; Goldman, M. V. +6 more
Kinetic simulations of magnetotail reconnection have revealed electromagnetic whistlers originating near the exhaust boundary and propagating into the inflow region. The whistler production mechanism is not a linear instability, but rather is Čerenkov emission of almost parallel whistlers from localized moving clumps of charge (finite-size quasipa…
Evidence for Bouncing Evolution Before Inflation After BICEP2
Zhang, Xinmin; Xia, Jun-Qing; Li, Hong +1 more
The BICEP2 Collaboration reports a detection of primordial cosmic microwave background (CMB) B mode with a tensor-to-scalar ratio r =0.20-0.05+0.07 (68% C.L.). However, this result disagrees with the recent Planck limit r<0.11 (95% C.L.) on constraining inflation models. In this Letter we consider an inflationary cosmology with a preceding nons…
Quantifying the BICEP2-Planck Tension over Gravitational Waves
Smith, Kendrick M.; Dvorkin, Cora; Boyle, Latham +4 more
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 signi…
Search for Gravitational Waves Associated with γ-ray Bursts Detected by the Interplanetary Network
Lee, H. M.; Cline, T.; Hurley, K. +899 more
We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significan…