Search Publications
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…
Electron Dynamics in the Diffusion Region of an Asymmetric Magnetic Reconnection
Fazakerley, A. N.; André, M.; Vaivads, A. +2 more
During a magnetopause crossing near the subsolar point Cluster observes the ion diffusion region of antiparallel magnetic reconnection. The reconnecting plasmas are asymmetric, differing in magnetic field strength, density, and temperature. Spatial changes in the electron distributions in the diffusion region are resolved and investigated in detai…
Limits on a Gravitational Field Dependence of the Proton-Electron Mass Ratio from H2 in White Dwarf Stars
Barstow, M. A.; Bagdonaite, J.; Salumbides, E. J. +4 more
Spectra of molecular hydrogen (H2) are employed to search for a possible proton-to-electron mass ratio (µ) dependence on gravity. The Lyman transitions of H2, observed with the Hubble Space Telescope towards white dwarf stars that underwent a gravitational collapse, are compared to accurate laboratory spectra taking int…
Backward Wave Cyclotron-Maser Emission in the Auroral Magnetosphere
Kellett, B. J.; Vorgul, I.; Bingham, R. +4 more
In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the radiation, generated by a down-going electron horseshoe distribution is due to a backward-wave cyclotron-maser emission process…