127 results found
Contaldi CR, 2011, The OPERA neutrino velocity result and the synchronisation of clocks
The CERN-OPERA experiment claims to have measured a one-way speed ofneutrinos that is apparently faster than the speed of light c. One-way speedmeasurements such as these inevitably require a convention for thesynchronisation of clocks in non-inertial frames since the Earth is rotating.We argue that the effect of the synchronisation convention is not properlytaken into account in the OPERA analysis and may well invalidate theirinterpretation of superluminal neutrino velocity.
O'Dea DT, Ade PAR, Amiri M, et al., 2011, Spider Optimization II: Optical, Magnetic and Foreground Effects, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 738
Spider is a balloon-borne instrument designed to map the polarization of thecosmic microwave background (CMB) with degree-scale resolution over a largefraction of the sky. Spider's main goal is to measure the amplitude ofprimordial gravitational waves through their imprint on the polarization of theCMB if the tensor-to-scalar ratio, r, is greater than 0.03. To achieve thisgoal, instrumental systematic errors must be controlled with unprecedentedaccuracy. Here, we build on previous work to use simulations of Spiderobservations to examine the impact of several systematic effects that have beencharacterized through testing and modeling of various instrument components. Inparticular, we investigate the impact of the non-ideal spectral response of thehalf-wave plates, coupling between focal plane components and the Earth'smagnetic field, and beam mismatches and asymmetries. We also present a model ofdiffuse polarized foreground emission based on a three-dimensional model of theGalactic magnetic field and dust, and study the interaction of this foregroundemission with our observation strategy and instrumental effects. We find thatthe expected level of foreground and systematic contamination is sufficientlylow for Spider to achieve its science goals.
Rocha G, Contaldi CR, Bond JR, et al., 2011, Application of XFASTER power spectrum and likelihood estimator to Planck, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 414, Pages: 823-846, ISSN: 0035-8711
Tamanini N, Contaldi CR, 2011, Inflationary perturbations in Palatini generalized gravity, PHYSICAL REVIEW D, Vol: 83, ISSN: 2470-0010
Thomas DB, Contaldi CR, 2011, Testing model independent modified gravity with future large scale surveys
Fraisse AA, Ade PAR, Amiri M, et al., 2011, SPIDER: Probing the Early Universe with a Suborbital Polarimeter
Filippini JP, Ade PAR, Amiri M, et al., 2011, SPIDER: a balloon-borne CMB polarimeter for large angular scales
Runyan MC, Ade PAR, Amiri M, et al., 2011, Design and performance of the Spider instrument
Natoli P, De Troia G, Hikage C, et al., 2010, BOOMERanG constraints on primordial non-Gaussianity from analytical Minkowski functionals, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 408, Pages: 1658-1665, ISSN: 0035-8711
Rocha G, Contaldi CR, Colombo LPL, et al., 2010, Performance of XFaster likelihood in real CMB experiments
We assess the strengths and weaknesses of several likelihood formalisms,including the XFaster likelihood. We compare the performance of the XFasterlikelihood to that of the Offset Lognormal Bandpower likelihood on simulateddata for the Planck satellite. Parameters estimated with these two likelihoodsare in good agreement. The advantages of the XFaster likelihood can thereforebe realized without compromising performance.
Contaldi C, Dowker F, Philpott L, 2010, Polarization Diffusion from Spacetime Uncertainty, Classical and Quantum Gravity, Vol: 27, ISSN: 0264-9381
A model of Lorentz invariant random fluctuations in photon polarization ispresented. The effects are frequency dependent and affect the polarization ofphotons as they propagate through space. We test for this effect by confrontingthe model with the latest measurements of polarization of Cosmic MicrowaveBackground (CMB) photons.
Bryan SA, Ade PAR, Amiri M, et al., 2010, Modeling and characterization of the SPIDER half-wave plate, MILLIMETER, SUBMILLIMETER, AND FAR-INFRARED DETECTORS AND INSTRUMENTATION FOR ASTRONOMY V, Vol: 7741, ISSN: 0277-786X
Nicholson G, Contaldi CR, Paykari P, 2010, Reconstruction of the primordial power spectrum by direct inversion, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, ISSN: 1475-7516
Gudmundsson JE, Ade PAR, Amiri M, et al., 2010, Thermal architecture for the SPIDER flight cryostat, Pages: 77411M-77411M
Himmetoglu B, Contaldi CR, Peloso M, 2009, Ghost instabilities of cosmological models with vector fields nonminimally coupled to the curvature, PHYSICAL REVIEW D, Vol: 80, ISSN: 2470-0010
Thomas DB, Contaldi CR, Magueijo J, 2009, Rotation of Galaxies as a Signature of Cosmic Strings in Weak Lensing Surveys, PHYSICAL REVIEW LETTERS, Vol: 103, ISSN: 0031-9007
Migliaccio M, Natoli P, De Troia G, et al., 2009, Probing primordial non Gaussianity in the BOOMERanG CMB maps: an analysis based on analytical Minkowski functionals, Galileo-Galilei-Institute Conference on Dark Matter and Dark Energy, Publisher: ELSEVIER SCIENCE BV, Pages: 278-286, ISSN: 0920-5632
Veneziani M, Amblard A, Cooray A, et al., 2009, SUBDEGREE SUNYAEV-ZEL'DOVICH SIGNAL FROM MULTIFREQUENCY BOOMERANG OBSERVATIONS, ASTROPHYSICAL JOURNAL LETTERS, Vol: 702, Pages: L61-L65, ISSN: 2041-8205
Nicholson G, Contaldi CR, 2009, Reconstruction of the primordial power spectrum using temperature and polarisation data from multiple experiments, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, ISSN: 1475-7516
Reichardt CL, Ade PAR, Bock JJ, et al., 2009, HIGH-RESOLUTION CMB POWER SPECTRUM FROM THE COMPLETE ACBAR DATA SET, ASTROPHYSICAL JOURNAL, Vol: 694, Pages: 1200-1219, ISSN: 0004-637X
Himmetoglu B, Contaldi CR, Peloso M, 2009, Instability of Anisotropic Cosmological Solutions Supported by Vector Fields, PHYSICAL REVIEW LETTERS, Vol: 102, ISSN: 0031-9007
Aguirre J, Amblard A, Ashoorioon A, et al., 2009, Observing the Evolution of the Universe
How did the universe evolve? The fine angular scale (l>1000) temperature andpolarization anisotropies in the CMB are a Rosetta stone for understanding theevolution of the universe. Through detailed measurements one may addresseverything from the physics of the birth of the universe to the history of starformation and the process by which galaxies formed. One may in addition trackthe evolution of the dark energy and discover the net neutrino mass. We are at the dawn of a new era in which hundreds of square degrees of skycan be mapped with arcminute resolution and sensitivities measured inmicroKelvin. Acquiring these data requires the use of special purposetelescopes such as the Atacama Cosmology Telescope (ACT), located in Chile, andthe South Pole Telescope (SPT). These new telescopes are outfitted with a newgeneration of custom mm-wave kilo-pixel arrays. Additional instruments are inthe planning stages.
Himmetoglu B, Contaldi CR, Peloso M, 2009, Instability of the Ackerman-Carroll-Wise model, and problems with massive vectors during inflation, PHYSICAL REVIEW D, Vol: 79, ISSN: 2470-0010
Dodelson S, Easther R, Hanany S, et al., 2009, The Origin of the Universe as Revealed Through the Polarization of the Cosmic Microwave Background
Modern cosmology has sharpened questions posed for millennia about the originof our cosmic habitat. The age-old questions have been transformed into twopressing issues primed for attack in the coming decade: How did the Universebegin? and What physical laws govern the Universe at the highest energies? Theclearest window onto these questions is the pattern of polarization in theCosmic Microwave Background (CMB), which is uniquely sensitive to primordialgravity waves. A detection of the special pattern produced by gravity waveswould be not only an unprecedented discovery, but also a direct probe ofphysics at the earliest observable instants of our Universe. Experiments whichmap CMB polarization over the coming decade will lead us on our first stepstowards answering these age-old questions.
Sievers JL, Mason BS, Weintraub L, et al., 2009, Cosmological Results from Five Years of 30 GHz CMB Intensity Measurements with the Cosmic Background Imager
We present final results on the angular power spectrum of total intensityanisotropies in the CMB from the CBI. Our analysis includes all primordialanisotropy data collected between January 2000 and April 2005, and benefitssignificantly from an improved maximum likelihood analysis pipeline. It alsoincludes results from a 30 GHz foreground survey conducted with the Green BankTelescope (GBT) which places significant constraints on the possiblecontamination due to foreground point sources. We improve on previous CBIresults by about a factor of two in the damping tail. These data confirm, at~3-sigma, the existence of an excess of power over intrinsic CMB anisotropy onsmall angular scales (l > 1800). Using the GBT survey, we find currently knownradio source populations are not capable of generating the power; a newpopulation of faint sources with steeply rising spectral indices would berequired to explain the excess with sources... We also present a fullcosmological parameter analysis of the new CBI power spectrum... With CBIalone, the full parameter analysis finds the excess is 1.6-sigma above thelevel expected for a sigma_8=0.8 universe. We find the addition of high-l CMBdata substantially improves constraints on cosmic string contributions to theTT power spectrum as well as the running of the scalar spectral index... Wealso present forecasts for what other experiments should see at differentfrequencies and angular resolutions given the excess power observed by CBI. Wefind that the reported high-l bandpowers from current high resolution CMBbolometer experiments are consistent with each other and CBI if the excesspower is due to the SZE at the CBI-level of 2.5 +/- 1 times the sigma_8=0.8standard SZ template. <Abridged>
MacTavish CJ, Ade PAR, Battistelli ES, et al., 2008, SPIDER OPTIMIZATION: PROBING THE SYSTEMATICS OF A LARGE-SCALE B-MODE EXPERIMENT, ASTROPHYSICAL JOURNAL, Vol: 689, Pages: 655-665, ISSN: 0004-637X
Gümrükçüoǧlu AE, Contaldi CR, Peloso M, 2008, CMB anomalies from relic anisotropy, Pages: 1641-1646
Most of the analysis of the Cosmic Microwave Background relies on the assumption of statistical isotropy. However, given some recent evidence pointing against isotropy, as for instance the observed alignment of different multipoles on large scales, it is worth testing this assumption against the increasing amount of available data. As a pivot model, we assume that the spectrum of the primordial perturbations depends also on their directionality (rather than just on the magnitude of their momentum, as in the standard case). We explicitly compute the correlation matrix for the temperature anisotropics in the simpler case in which there is a residual isotropy between two spatial directions. As a concrete example, we consider a different initial expansion rate along one direction, and the following isotropization which takes place during inflation. Depending on the amount of inflation, this can lead to broken statistical isotropy on the largest observable scales. © 2008 World Scientific Publishing Co. Pte. Ltd.
Contaldi CR, Magueijo J, Smolin L, 2008, Anomalous cosmic-microwave-background polarization and gravitational chirality, PHYSICAL REVIEW LETTERS, Vol: 101, ISSN: 0031-9007
Contaldi CR, Wiseman T, Withers B, 2008, TeVeS gets caught on caustics, PHYSICAL REVIEW D, Vol: 78, ISSN: 1550-7998
Contaldi CR, Nicholson G, Stoica H, 2008, Small cosmological signatures from multi-brane models
We analyse the signatures of brane inflation models with modulistabilisation. These are hybrid inflation models with a non-trivial field-spacemetric which can induce complex trajectories for the fields during inflation.This in turn could lead to observable features on the power spectrum of the CMBfluctuations through departures from near scale invariance or the presence ofisocurvature modes. We look specifically at multi-brane models in which thevolume modulus also evolves. We find that the signatures are highly sensitiveto the actual trajectories in field space, but their amplitudes are too smallto be observable even for future high precision CMB experiments.
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