Principles of Physical Cosmology

Peebles, Patrick; Harrison, Edward

doi:10.1119/1.17585

Cited by 266 publications

(353 citation statements)

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“…If galaxy distribution turns out to be homogeneous at λ 0 ≈ 10h −1 M pc then Ω ≈ 6 · 10 −3 as it is obtained in the standard treatment 40 . If, instead, the crossover to homogeneity lies at 100h −1 M pc, we obtain Ω ≈ 6 · 10 −4 .…”

Section: Average Luminosity Density From Galaxy Catalogsmentioning

confidence: 99%

“…As there is still some controversy about the value of λ 0 46,49,7,30,34 we give the estimation as a function of λ 0 . We stress that the way this estimation is performed, is substantially different from the usual one 40 , because in such a case the fractal behavior is not considered at all, and one assumes a perfect homogeneous distribution at relatively small scale (λ 0 ∼ 5 ÷ 10h −1 M pc). This situation is clearly not the one corresponding to the more "optimistic" estimation of the homogeneity scale λ 0 46,49,30 .…”

Section: Estimation Of the Average Luminosity And Mass Densitymentioning

confidence: 99%

“…Essentially all the currently elaborated models of galaxy formation 40 assume large scale homogeneity and predict that the galaxy power spectrum (hereafter PS), which is the PS of the density contrast, decreases both toward small scales and toward large scales, with a turnaround somewhere in the middle, at a scale λ f that can be taken as separating "small" from "large" scales. Because of the homogeneity assumption, the PS amplitude should be independent on the survey scale, any residual variation being attributed to luminosity bias (or to the fact that the survey scale has not yet reached the homogeneity scale).…”

Section: Power Spectrum Of Density Fluctuationsmentioning

confidence: 99%

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Fractal structures and the large scale distribution of galaxies

Pietronero

Labini

2001

Current Topics in Astrofundamental Physics: The Cosmic Microwave Background

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Galaxy structures are certainly fractal up to a certain crossover scale λ 0 . A clear determination of such a scale is still missing. Usually the conceptual and practical implications of this property are neglected and the structures are only discussed in terms of their global amplitude. Here we present a compact summary of these implications. First, we discuss the problem of the identification of the crossover scale λ 0 and the proper characterization of the scaling. We then consider the implications of these properties with respect to various physical phenomena and to the corresponding characteristic values, i.e. r 0 , σ 8 , Ω, etc. These implications crucially depend on the value of λ 0 , but they are still important for a relatively small value, say λ 0 ≈ 50h −1 M pc. Finally we consider the main theoretical consequences of these results.

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Section: Average Luminosity Density From Galaxy Catalogsmentioning

confidence: 99%

Section: Estimation Of the Average Luminosity And Mass Densitymentioning

confidence: 99%

Section: Power Spectrum Of Density Fluctuationsmentioning

confidence: 99%

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Fractal structures and the large scale distribution of galaxies

Pietronero

Labini

2001

Current Topics in Astrofundamental Physics: The Cosmic Microwave Background

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“…The separation of the Gaussian and the non-Gaussian scales can be related to the correlation length usually taken as r c 5h −1 Mpc, which is the scale at which the two-point correlation function is unity,i.e. ξ(r c ) = 1 [18]. For h = 0.7 this scale is r c 7 Mpc, and for scales larger than the correlation length, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…where the window function W ( z) is given by the Heaviside function: [24,26] The velocity vector can be expressed in Fourier space since, 5) and the peculiar velocity v k and the density perturbations δ k in the linear regime are simply related through [18]:…”

Section: Introductionmentioning

confidence: 99%

Critical points of the cosmic velocity field and the uncertainties in the value of the Hubble constant

Liu¹,

Mohayaee²,

Naselsky³

2016

J. Cosmol. Astropart. Phys.

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Abstract. The existence of critical points for the peculiar velocity field is a natural feature of the correlated vector field. These points appear at the junctions of velocity domains with different orientations of their averaged velocity vectors. Since peculiar velocities are the important cause of the scatter in the Hubble expansion rate, we propose that a more precise determination of the Hubble constant can be made by restricting analysis to a subsample of observational data containing only the zones around the critical points of the peculiar velocity field, associated with voids and saddle points. On large-scales the critical points, where the first derivative of the gravitational potential vanishes, can easily be identified using the density field and classified by the behavior of the Hessian of the gravitational potential. We use high-resolution N-body simulations to show that these regions are stable in time and hence are excellent tracers of the initial conditions. Furthermore, we show that the variance of the Hubble flow can be substantially minimized by restricting observations to the subsample of such regions of vanishing velocity instead of aiming at increasing the statistics by averaging indiscriminately using the full data sets, as is the common approach.

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Retracted: New aspects of photon propagation in expanding universes

Fahr

Heyl

2017

Astron Nachr

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Background: Modern cosmology assumes that the cosmic microwave background (CMB) radiation is a relict of the much hotter electromagnetic radiation field from the early recombination era of the universe. Its present very low radiation temperature T CMB = 2.735 K thereby is explained by the fact that the cosmic photons in the expanding universe undergo a wavelength stretching according to 𝜆/𝜆0 = S/S 0 , where S denotes the scale of the universe. The present-day CMB temperature hence simply expresses the factor by which the universe has grown since the recombination era. Materials and Methods: On the basis of well-known facts of Special and General Relativity (SRT and GRT), we reinvestigate the behavior of freely propagating cosmic photons in dynamic Robertson-Walker spacetime geometries and show that in the system of the propagating photon, due to the fact that no time lapses in this proper system, the photon does not change its initial state, that is, its wavelength and energy. We do, however, also show that the global beat of the time changes with the cosmic world time or the cosmic scale S. That means cosmic photons do not change their state, till they are registered by a local detector, that is, a local clock. Results: We claim that the energy density of cosmic photons which enters the energy-momentum tensor of Einstein's GRT field equations does not scale like S −4 as assumed in present-day cosmology, but like S −3 , that is, identically to the behavior of the energy densities of baryonic or dark matter, meaning that the energy density of photons in the present-day universe cannot be neglected, but counts substantially for the expansion history of the universe. Nevertheless, we show that cosmic photons measured with a present-day detector (local clock) locally will show their cosmological redshift, explaining the present-day CMB Planck spectrum with a Planck temperature of 2.735 K. Conclusions: As the energy density of cosmic photons cannot be neglected, their contribution in the GRT energy-momentum tensor is important over all phases of the expansion of the universe. They are thus acting identical to the way how dark matter acts and influences cosmic expansion. This means that the present-day claim for a dark matter contribution in cosmic expansion by Ω dark ≃ 0.23 can be substantially relaxed.

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Principles of Physical Cosmology

Cited by 266 publications

References 0 publications

Fractal structures and the large scale distribution of galaxies

Fractal structures and the large scale distribution of galaxies

Critical points of the cosmic velocity field and the uncertainties in the value of the Hubble constant

Retracted: New aspects of photon propagation in expanding universes

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