共查询到20条相似文献,搜索用时 15 毫秒
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S. L. Bridle I. Zehavi A. Dekel O. Lahav M. P. Hobson A. N. Lasenby 《Monthly notices of the Royal Astronomical Society》2001,321(2):333-340
We compare and combine likelihood functions of the cosmological parameters Ωm , h and σ 8 , from peculiar velocities, cosmic microwave background (CMB) and type Ia supernovae. These three data sets directly probe the mass in the Universe, without the need to relate the galaxy distribution to the underlying mass via a 'biasing' relation. We include the recent results from the CMB experiments BOOMERANG and MAXIMA-1. Our analysis assumes a flat Λ cold dark matter (ΛCDM) cosmology with a scale-invariant adiabatic initial power spectrum and baryonic fraction as inferred from big-bang nucleosynthesis. We find that all three data sets agree well, overlapping significantly at the 2 σ level. This therefore justifies a joint analysis, in which we find a joint best-fitting point and 95 per cent confidence limits of (0.17,0.39), (0.64,0.86) and (0.98,1.37). In terms of the natural parameter combinations for these data (0.40,0.73), (0.16,0.27). Also for the best-fitting point, and the age of the Universe is 13.2 Gyr. 相似文献
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The fluctuations of the cosmic microwave background (CMB) are investigated for a hyperbolic universe with finite volume. Four-component models with radiation, matter, vacuum energy and an extra spatially constant dark energy X -component are considered. The general solution of the Friedmann equation for the cosmic scalefactor a ( η ) is given for the four-component models in terms of the Weierstrass ℘-function. The lower parts of the angular power spectra C l of the CMB anisotropy are computed for nearly flat models with Ωtot ≤0.95. It is shown that the particular compact fundamental cell that is considered in this paper leads to a suppression in C l for l ≲10 and Ωtot ≲0.9. 相似文献
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Parameter constraints for flat cosmologies from cosmic microwave background and 2dFGRS power spectra
Will J. Percival Will Sutherland John A. Peacock Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Stephen Moody Peder Norberg Bruce A. Peterson Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,337(3):1068-1080
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Cosmological parameters from cosmic microwave background measurements and the final 2dF Galaxy Redshift Survey power spectrum 总被引:1,自引:0,他引:1
Ariel G. Sánchez C. M. Baugh W. J. Percival J. A. Peacock N. D. Padilla S. Cole C. S. Frenk P. Norberg 《Monthly notices of the Royal Astronomical Society》2006,366(1):189-207
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G.Efstathiou StephenMoody John A.Peacock Will J.Percival CarltonBaugh JossBland-Hawthorn TerryBridges RussellCannon ShaunCole MatthewColless ChrisCollins WarrickCouch GavinDalton Roberto DePropris Simon P.Driver Richard S.Ellis Carlos S.Frenk KarlGlazebrook CaroleJackson OferLahav IanLewis StuartLumsden SteveMaddox PederNorberg Bruce A.Peterson WillSutherland KeithTaylor 《Monthly notices of the Royal Astronomical Society》2002,330(2):L29-L35
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Krzysztof Bolejko † rzej Krasiski † Charles Hellaby † 《Monthly notices of the Royal Astronomical Society》2005,362(1):213-228
We develop models of void formation starting from a small initial fluctuation at recombination and growing to a realistic present-day density profile in agreement with observations of voids. The model construction is an extension of previously developed algorithms for finding a Lemaître–Tolman metric that evolves between two profiles of either density or velocity specified at two times. Of the four profiles of concern (those of density and velocity at recombination and at the present day), two can be specified and the other two follow from the derived model.
We find that, in order to reproduce the present-day void density profiles, the initial velocity profile is more important than the initial density profile.
Extrapolation of current cosmic microwave background (CMB) observations to the scales relevant to protovoids is very uncertain. Even so, we find that it is very difficult to make both the initial density and velocity fluctuation amplitudes small enough and still obtain a realistic void by today. 相似文献
We find that, in order to reproduce the present-day void density profiles, the initial velocity profile is more important than the initial density profile.
Extrapolation of current cosmic microwave background (CMB) observations to the scales relevant to protovoids is very uncertain. Even so, we find that it is very difficult to make both the initial density and velocity fluctuation amplitudes small enough and still obtain a realistic void by today. 相似文献
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G. Efstathiou 《Monthly notices of the Royal Astronomical Society》2002,332(1):193-198
A principal-component analysis of cosmic microwave background (CMB) anisotropy measurements is used to investigate degeneracies among cosmological parameters. The results show that a degeneracy with tensor modes – the 'tensor degeneracy'– dominates uncertainties in estimates of the baryon and cold dark matter densities, ω b =Ωb h 2 , ω c =Ωc h 2 , 1 from an analysis of CMB anisotropies alone. The principal-component analysis agrees well with a maximum-likelihood analysis of the observations, identifying the main degeneracy directions and providing an impression of the effective dimensionality of the parameter space. 相似文献
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D. L. Harrison J. A. Rubiño-Martin S. J. Melhuish R. A. Watson R. D. Davies R. Rebolo R. J. Davis C. M. Gutiérrez J. F. Macias-Perez 《Monthly notices of the Royal Astronomical Society》2000,316(2):L24-L28
This paper presents the results from the Jodrell BankInstituto de Astrofisicia de Canarias (IAC) two-element 33-GHz interferometer operated with an element separation of 32.9 wavelengths and hence sensitive to 1°-scale structure on the sky. The level of cosmic microwave background (CMB) fluctuations, assuming a flat CMB spatial power spectrum over the range of multipoles =208±18, was found using a likelihood analysis to be at the 68 per cent confidence level, after the subtraction of the contribution of monitored point sources. Other possible foreground contributions have been assessed and are expected to have negligible impact on this result. 相似文献
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In this paper we investigate the effects of perturbations in a dark energy component with a constant equation of state on large-scale cosmic microwave background (CMB) anisotropies. The inclusion of perturbations increases the large-scale power. We investigate more speculative dark energy models with w < −1 and find the opposite behaviour. Overall the inclusion of perturbations in the dark energy component increases the degeneracies. We generalize the parametrization of the dark energy fluctuations to allow for an arbitrary constant sound speed, and we show how constraints from CMB experiments change if this is included. Combining CMB with large-scale structure, Hubble parameter and supernovae observations we obtain w =−1.02 ± 0.16 (1σ) as a constraint on the equation of state, which is almost independent of the sound speed chosen. With the presented analysis we find no significant constraint on the constant speed of sound of the dark energy component. 相似文献
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A. F. Heavens 《Monthly notices of the Royal Astronomical Society》1998,299(3):805-808
The bispectrum of the microwave background sky is a possible discriminator between inflationary and defect models of structure formation in the Universe. The bispectrum, which is the analogue of the temperature three-point correlation function in harmonic space, is zero for most inflationary models, but non-zero for non-Gaussian models. The expected departures from zero are small, and easily masked by noise, so it is important to be able to estimate the bispectrum coefficients as accurately as possible, and to know the errors and correlations between the estimates so that they may be used in combination as a diagnostic to rule out non-Gaussian models. This paper presents a method for estimating in an unbiased way the bispectrum from a microwave background map in the near-Gaussian limit. The method is optimal, in the sense that no other method can have smaller error bars, and, in addition, the covariances between the bispectrum estimates are calculated explicitly. The method deals automatically with partial sky coverage and arbitrary noise correlations without modification. A preliminary application to the Cosmic Background Explorer 4-yr data set shows no evidence for non-Gaussian behaviour. 相似文献
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Licia Verde Limin Wang Alan F. Heavens Marc Kamionkowski 《Monthly notices of the Royal Astronomical Society》2000,313(1):141-147
Cosmic microwave background and large-scale structure data will shortly improve dramatically with the Microwave Anisotropy Probe and Planck Surveyor , and the Anglo-Australian 2-Degree Field and Sloan Digital Sky Survey. It is therefore timely to ask which of the microwave background and large-scale structure will provide a better probe of primordial non-Gaussianity. In this paper we consider this question, using the bispectrum as a discriminating statistic. We consider several non-Gaussian models and find that in each case the microwave background will provide a better probe of primordial non-Gaussianity. Our results suggest that if microwave background maps appear Gaussian, then apparent deviations from Gaussian initial conditions in galaxy surveys can be attributed with confidence to the effects of biasing. We demonstrate this precisely for the spatial bispectrum induced by local non-linear biasing. 相似文献