Observations in the Einstein-De Sitter cosmology: Dust statistics and limits of apparent homogeneity

Ribeiro, Marcelo B.

doi:10.1086/175374

Cited by 27 publications

(77 citation statements)

References 11 publications

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“…Moreover, as they are using a flux limited sample, another (1 + z) factor must be considered when changing from bolometric to flux limited measures (Ellis 1971, p. 161 (2000) pointed out that locally the cold dark matter and fractal models predict the same behaviour for the power spectrum, a conclusion apparently shared by Cappi et al (1998). In addition, confirming Ribeiro's (1992bRibeiro's ( , 1995 conclusions, departures from the expected Euclidean results at small redshifts were also reported by Longair (1995, p. 398), and the starting point for his findings was the same as employed in here and by Ribeiro (1992bRibeiro ( , 1995: the use of source number count expression along the null cone.…”

Section: Some Common Misconceptionsmentioning

confidence: 79%

“…As the Hubble law is a distance-redshift law, derived from the first order expansions of the distances, it is clear that due to the non-linearity of the Einstein field equations, observational relations behave differently at different redshift depths. Consequently, while the linearity of the Hubble law is well preserved in the EdS model up to z ≈ 1 (Ribeiro 1995), a value implicitly assumed as the lower limit up to where relativistic effects could be safely ignored, the observational average densities constructed with d ℓ , d A , and z are strongly affected by relativistic effects at much lower redshift values. Then, while the zeroth order term vanishes in the distance-redshift relation, it is non-zero for the average density as plotted against redshift.…”

Section: An Example: the Einstein-de Sitter Cosmologymentioning

confidence: 99%

“…In other words, we need to derive new observational relations capable of taking into account the lookback time. This section also revisits some of Ribeiro's (1995) results, showing that the linearity of the distance-redshift relation does not help in the context of observational characterization of cosmological density as this relation remains well approximated by a linear relation throughout moderate redshift ranges, without any change in the value of H 0 . Thus, it cannot be used as a test for possible dismissal of largescale hierarchical (fractal) clustering, as has been done in the past (Sandage, Tammann and Hardy 1972;Sandage and Tammann 1975).…”

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confidence: 91%

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The Apparent Fractal Conjecture: Scaling Features in Standard Cosmologies

Ribeiro¹

2001

General Relativity and Gravitation

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This paper presents an analysis of the smoothness problem in cosmology by focussing on the ambiguities originated in the simplifying hypotheses aimed at observationally verifying if the large-scale distribution of galaxies is homogeneous, and conjecturing that this distribution should follow a fractal pattern, in the sense of having a power-law type average density profile, in perturbed standard cosmologies. This is due to a geometrical effect, appearing when certain types of average densities are calculated along the past light cone. The paper starts by reviewing the argument concerning the possibility that the galaxy distribution follows such a scale invariant pattern, and the premises behind the assumption that the spatial homogeneity of standard cosmology can be observable. Next, it is argued that in order to discuss observable homogeneity one needs to make a clear distinction between local and average relativistic densities, and showing how the different distance definitions strongly affect them, leading the various average densities to display asymptotically opposite behaviours. Then the paper revisits Ribeiro's (1995) results, showing that in a fully relativistic treatment some observational average densities of the flat Friedmann model are not well defined at z ∼ 0.1, implying that at this range average densities behave in a fundamentally different manner as compared to the linearity of the Hubble law, well valid for z < 1. This conclusion brings into question the widespread assumption that relativistic corrections can always be neglected at low z. It is also shown how some key features of fractal cosmologies can be found in the Friedmann models. In view of those findings, it is suggested that the so-called contradiction between the cosmological principle, and the galaxy distribution forming an unlimited fractal structure, may not exist. John Maynard Keynes (1936)

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Section: Some Common Misconceptionsmentioning

confidence: 79%

Section: An Example: the Einstein-de Sitter Cosmologymentioning

confidence: 99%

mentioning

confidence: 91%

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The Apparent Fractal Conjecture: Scaling Features in Standard Cosmologies

Ribeiro¹

2001

General Relativity and Gravitation

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“…These quantities are useful in determining whether or not, and within what ranges, a spatially homogeneous cosmological model can or cannot be observationally homogeneous as well (Ribeiro 1995(Ribeiro , 2005Rangel Lemos & Ribeiro 2008). This is because these densities behave very differently depending on the distance measure used in their definitions -that is, they show a strong dependence on the cosmological distance adopted.…”

Section: Differential and Integral Densitiesmentioning

confidence: 99%

Relativistic cosmology number densities and the luminosity function

Iribarrem¹,

Lopes²,

Ribeiro³

et al. 2012

A&A

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Aims. This paper studies the connection between the relativistic number density of galaxies down the past light cone in a FriedmannLemaître-Robertson-Walker spacetime with non-vanishing cosmological constant and the galaxy luminosity function (LF) data. It extends the redshift range of previous results presented in Albani et al. (2007, ApJ, 657, 760), where the galaxy distribution was studied out to z = 1. Observational inhomogeneities were detected at this range. This research also searches for LF evolution in the context of the framework advanced by Ribeiro and Stoeger (2003, ApJ, 592, 1), further developing the theory linking relativistic cosmology theory and LF data. Methods. Selection functions are obtained using the Schechter parameters and redshift parametrization of the galaxy LF obtained from an I-band selected dataset of the FORS deep field galaxy survey in the redshift range 0.5 ≤ z ≤ 5.0 for its blue bands and 0.75 ≤ z ≤ 3.0 for its red ones. Differential number counts, densities and other related observables are obtained, and then used with the calculated selection functions to study the empirical radial distribution of the galaxies in a fully relativistic framework. Results. The redshift range of the dataset used in this work, which is up to five times larger than the one used in previous studies, shows an increased relevance of the relativistic effects of expansion when compared to the evolution of the LF at the higher redshifts. The results also agree with the preliminary ones presented in Albani et al., suggesting a power-law behavior of relativistic densities at high redshifts when they are defined in terms of the luminosity distance.

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“…However, from the analysis presented by Ribeiro (1995) it is clear that this is not a paradox, but just very different relativistic effects on the observables at the moderate redshift range (0.1 ≤ z < 1).…”

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confidence: 99%

The Apparent Fractal Conjecture

Ribeiro

2001

Fractals

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This short communication advances the hypothesis that the observed fractal structure of large-scale distribution of galaxies is due to a geometrical effect, which arises when observational quantities relevant for the characterization of a cosmological fractal structure are calculated along the past light cone. If this hypothesis proves, even partially, correct, most, if not all, objections raised against fractals in cosmology may be solved. For instance, under this view the standard cosmology has zero average density, as predicted by an infinite fractal structure, with, at the same time, the cosmological principle remain- The issue of whether or not the large-scale distribution of matter in the Universe actually follows a fractal pattern has divided cosmologists in the last decade or so, with the debates around this thorny question leading to a split of opinions between two main, and opposing, groups.On one side, the orthodox view sustains that since a fractal structure is inhomogeneous, it cannot agree with what we know about the structure and evolution of the Universe, as this knowledge is based on the cosmological principle and the Friedmann-Lemaître-RobertsonWalker (FLRW) spacetime, with both predicting homogeneity for the universal distribution of matter. Moreover, inasmuch as the cosmic microwave background radiation (CMBR) is isotropic, a result predicted by the FLRW cosmology, this group is, understandably, not prepared to give up the standard FLRW universe model and the cosmological principle, as that would mean giving up most, if not all, of what we learned about the structure and evolution of the Universe since the dawn of cosmology

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Observations in the Einstein-De Sitter cosmology: Dust statistics and limits of apparent homogeneity

Cited by 27 publications

References 11 publications

The Apparent Fractal Conjecture: Scaling Features in Standard Cosmologies

The Apparent Fractal Conjecture: Scaling Features in Standard Cosmologies

Relativistic cosmology number densities and the luminosity function

The Apparent Fractal Conjecture

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