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On the perturbation of the luminosity distance by peculiar motions


We consider some aspects of the perturbation to the luminosity distance d(z) thatare of relevance for SN1a cosmology and for future peculiar velocity surveys at non-negligible redshifts.1) Previous work has shown that the correction to the lowest order perturba-tion d/d = −v/cz has the peculiar characteristic that it appears to depend on theabsolute state of motion of sources, rather than on their motion relative to that ofthe observer. The resolution of this apparent violation of the equivalence principle isthat it is necessary to allow for evolution of the velocities with time, and also, whenconsidering perturbations on the scale of the observer-source separation, to includethe gravitational red

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Correlated Fluctuations in Luminosity Distance and the Importance of Peculiar Motion in Supernova Surveys


Large scale structure introduces two different kinds of errors in the luminosity distance estimatesfrom standardizable candles such as supernovae Ia (SNe) – a Poissonian scatter for each SN and acoherent component due to correlated fluctuations between different SNe. Increasing the number ofSNe helps reduce the first type of error but not the second. The coherent component has been largelyignored in forecasts of dark energy parameter estimation from upcoming SN surveys. For instanceit is commonly thought, based on Poissonian considerations, that peculiar motion is unimportant,even for a low redshift SN survey such as the Nearby Supernova Factory (SNfactory; z

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Fluctuations of the luminosity distance


We derive an expression for the luminosity distance in a perturbed Friedmann universe. We definethe correlation function and the power spectrum of the luminosity distance fluctuations and expressthem in terms of the initial spectrum of the Bardeen potential. We present semi-analytical resultsfor the case of a pure CDM (cold dark matter) universe. We argue that the luminosity distancepower spectrum represents a new observational tool which can be used to determine cosmologicalparameters. In addition, our results shed some light into the debate whether second order smallscale fluctuations can mimic an accelerating universe.

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Galaxy Peculiar Velocities From Large-Scale Supernova Surveys as a Dark Energy Probe


Upcoming imaging surveys such as the Large Synoptic Survey Telescope will repeatedly scanlarge areas of sky and have the potential to yield million-supernova catalogs. Type Ia supernovae are excellent standard candles and will provide distance measures that suffice to detect mean pairwise velocities of their host galaxies. We show that when combining these distance measures with photometric redshifts for either the supernovae or their host galaxies, the mean pairwise velocities of the host galaxies will provide a dark energy probe which is competitive with other widely discussed methods. Adding information from this test to type Ia supernova photometric luminosity distances from the sa

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The Luminosity Distance in Perturbed FLRW Spacetimes


ABSTRACTWe derive an expression for the luminosity distance in FLRW spacetimes affectedby scalar perturbations. Our expression is complete to linear order and is expressedentirely in terms of standard cosmological parameters and observational quantities.Weillustrate the result by calculating the RMS scatter in the usual luminosity distancein flat (m) = (1.0, 0.0) and (0.3, 0.7) cosmologies. In both cases the scatter isappreciable at high redshifts, and rises above 11% at z = 2, where it may be thedominant noise term in the Hubble diagram based on SN Ia.

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ACDM model with a scalar perturbation vs preferred direction of the universe


 We present a scalar perturbation for the CDM model, which breaks the isotropic symmetry of the universe. Based on the Union2 data, the least-2 fit of the scalar perturbed CDM modelshows that the universe has a preferred direction (l, b) = (287◦ ?? 25◦, 11◦ ?? 22◦). The magnitudeof scalar perturbation is about −2.3??10−5. The scalar perturbation for the CDM model impliesa peculiar velocity, which is perpendicular to the radial direction.Collaboration. 

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The second-order luminosity-redshift relation in a generic inhomogeneous cosmology


  After recalling a general non-perturbative expression for the luminosity-redshift relation holding in a recently proposed “geodesic light-cone” gauge, we show how it can be transformed to phenomenologically more convenient gauges in which cosmological perturbation theory is better understood We present, in particular, the complete result on the luminosity-redshift relation in the Poisson gauge up to second order for a fairly generic perturbed cosmology, assuming that appreciable vector and tensor perturbations are only generated at second order. This relation provides a basic ingredient for the computation of the effects of stochastic inhomogeneities on precision

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THE PECULIAR VELOCITIES OF LOCAL TYPE Ia SUPERNOVAE AND THEIR IMPACT ON COSMOLOGY


 We quantify the effect of supernova Type Ia peculiar velocities on the derivation of cosmological parameters. The published distant and local Ia SNe used for the Supernova Legacy Survey first-year cosmology report form the sample for this study. While previous work has assumed that the local SNe are at rest in the CMB frame (the No Flow assumption), we test this assumption by applying peculiar velocity corrections to the local SNe using three different flow models. The models are based on the IRAS PSCz galaxy redshift survey, have varying = 0.6m /b, and reproduce the Local Group motionin the CMB frame. These datasets are then fit for w, m, and using flatne

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Measuring our Peculiar Velocity by\"Pre-deboosting\" the CMB


It was recently shown that our peculiar velocity with respect to the CMB induces mixingamong multipoles and o-diagonal correlations at all scales which can be used as a measurementof , which is independent of the standard measurement using the CMB temperature dipole. Theproposed techniques rely however on a perturbative expansion which breaks down for ` & 1= 800.Here we propose a technique which consists of deboosting the CMB temperature in the time-ordereddata and show that it extends the validity of the perturbation analysis multipoles up to ` 10000.We also obtain accurate tting functions for the mixing between multipoles valid in a full non-linear treatment. Finally we forecast the achievable precis

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Measuring our Peculiar Velocity by Predeboosting the CMB


pdf It was recently shown that our peculiar velocity with respect to the CMB induces mixing among multipoles and o-diagonal correlations at all scales which can be used as a measurement of, which is independent of the standard measurement using the CMB temperature dipole. The proposed techniques rely however on a perturbative expansion which breaks down for ` & 1= 800 .Here we propose a technique which consists of deboosting the CMB temperature in the time-ordereddata and show that it extends the validity of the perturbation analysis multipoles up to` 10000.We also obtain accurate tting functions for the mixing between multipoles valid in a full non-linear treatment. Finally we forecast the achiev

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