Measuring Spacetime: From the Big Bang to Black Holes

Tegmark, Max

doi:10.1126/science.1072184

Cited by 32 publications

(31 citation statements)

References 83 publications

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“…Such an effect was first predicted by Hoyle [16], originally aiming at distinguishing the steady state and Einstein-de Sitter cosmologies. Later on, the accumulated evidence against the original version of the steady state model have put such a scenario aside, and more recently the same is occurring with the theoretically favoured critical density FRW model [17].…”

Section: The Critical Redshiftmentioning

confidence: 99%

The angular size–redshift relation in power-law cosmologies

Jain¹,

Dev²,

Alcaniz³

2003

Class. Quantum Grav.

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A linear evolution of the cosmological scale factor is a feature in several models designed to solve the cosmological constant problem via a coupling between scalar or tensor classical fields to the space-time curvature as well as in some alternative gravity theories. In this paper, by assuming a general time dependence of the scale factor, R ∼ t α , we investigate observational constraints on the dimensionless parameter α from measurements of the angular size for a large sample of milliarcsecond compact radio sources. In particular, we find that a strictly linear evolution, i.e., α ≃ 1 is favoured by these data, which is also in agreement with limits obtained from other independent cosmological tests. The dependence of the critical redshift zm (at which a given angular size takes its minimal value) with the index α is briefly discussed.

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Section: The Critical Redshiftmentioning

confidence: 99%

The angular size–redshift relation in power-law cosmologies

Jain¹,

Dev²,

Alcaniz³

2003

Class. Quantum Grav.

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“…One expects no relics per se, but there should be signatures in cosmic gravitational waves and in the details of the behavior of the dark energy. Some brane universe scenarios (Avelino & Martins 2002) also are said to preserve the good aspects of hot big bang but to provide alternatives to the less satisfactory ones, as are some of the extra-dimension theories (Starkman et al 2001;Randall 2002;Tegmark 2002;Liu & Wesson 2001;Khoury & Zhang 2002).…”

Section: Three For $5 With Your Amateur Cosmologist's Frequent Readermentioning

confidence: 99%

Astrophysics in 2002

Trimble

Aschwanden

2003

PUBL ASTRON SOC PAC

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ABSTRACT. This has been the Year of the Baryon. Some low temperature ones were seen at high redshift, some high temperature ones were seen at low redshift, and some cooling ones were (probably) reheated. Astronomers saw the back of the Sun (which is also made of baryons), a possible solution to the problem of ejection of material by Type II supernovae (in which neutrinos push out baryons), the production of R Coronae Borealis stars (previously-owned baryons), and perhaps found the missing satellite galaxies (whose failing is that they have no baryons). A few questions were left unanswered for next year, and an attempt is made to discuss these as well.

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“…Together with supernova data, analysis of the CBR angular anisotropies and in particular their peaks gives a concordance model of this kind [8,215,217,38,195] that is then confirmed by the statistics of matter clustering [48] together with observations of gravitational lensing and large-scale motions of matter [203]. This model is characterized by specific values for a set of cosmological parameters [139], in particular…”

Section: The Concordance Modelmentioning

confidence: 87%

“…Problems arise because of our lack of adequate theories of their historical development. It is useful here to distinguish between methods aimed at determining the properties of the background (zeroth order) FL model directly, and those aimed at determining properties of the perturbations of these models [215]. Methods for determining the parameters of the background model (Sec.2.1) depend on assuming properties of the distance indicators used (galaxies, radio sources, etc.).…”

Section: Determining the Model Parametersmentioning

confidence: 99%

“…By contrast, many of the methods of estimating Ω 0 (and to some degree Λ) depend on studying the growth and nature of inhomogeneities in the universe, that is they investigate perturbed FL models (Sec.2.5.2), whose properties of course depend on the background model, but introduce a whole set of further functions and parameters describing the perturbations [38], for example the angular correlation function for matter (or its Fourier transform, the 2-dimensional power spectrum), the power spectrum of density fluctuations [215], red-shift space correlation functions [164,48], and correlation function for velocities [38]. Associated parameters include a scalar spectral index (characterizing the spectrum of physical sizes of inhomogeneities), the bias parameter b (expressing how galaxy formation is biassed towards density peaks in the inhomogeneities ( [38], p. 280)) and the initial fluctuation magnitudes Q (the seeds for structure formation).…”

Section: Determining the Model Parametersmentioning

confidence: 99%

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Issues in the Philosophy of Cosmology

Ellis¹

2007

Philosophy of Physics

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After a survey of the present state of cosmological theory and observations, this article discusses a series of major themes underlying the relation of philosophy to cosmology. These are:A: The uniqueness of the universe; B: The large scale of the universe in space and time; C: The unbound energies in the early universe; D: Explaining the universe -the question of origins; E: The universe as the background for existence; F: The explicit philosophical basis; G: The Anthropic question: fine tuning for life; H: The possible existence of multiverses; I: The natures of existence. Each of these themes is explored and related to a series of Theses that set out the major issues confronting cosmology in relation to philosophy. IntroductionCosmology is the study of the large-scale structure of the Universe, where 'the Universe' means all that exists in a physical sense [104]. This is to be distinguished from the Observable Universe, namely that part of the Universe containing matter accessible to our astronomical observations, which is a subset of the Universe proper. Thus cosmology considers the vast domain of galaxies, clusters of galaxies, quasi-stellar objects, etc., observable in the sky by use of telescopes of all kinds, examining their nature, distribution, origins, and relation to their larger environment. Observational cosmology [114,128,99,189,18] aims to determine the large-scale geometry of the observable universe and the distribution of matter in it from observations of radiation emitted by distant objects, while physical cosmology [163,193,233,202,171,38] is the study of interactions during the expansion of the universe in its early hot big bang phase, and astrophysical cosmology [193,165,160,174,38] studies the resulting later development of large-scale structures such as galaxies and clusters of galaxies. Various forms of quantum cosmology (see e.g. [109,92,26]) and studies of particle physics aspects of cosmology [126,162,1,171,38] attempt to characterize the epochs before the hot big bang phase. These studies function in a mainly symbiotic way, each informing and supplementing the others to create an overall cosmological theory of the origin and evolution of the physical universe [14,104,201].A unique role of the universe is in creating the environment in which galaxies, stars, and planets develop, thus providing a setting in which local physics and chemistry can function in a way that enables the evolution of life on planets such as the Earth. If the cosmological environment were substantially different, local conditions would be different and in most cases we would not be here [21,29,7,214,175] -indeed no biological evolution at all would have taken place. Thus cosmology is of substantial interest to the whole of the scientific endeavor, for it sets the framework for the rest of science, and indeed for the very existence of observers and scientists. It is unique as the ultimate historical/geographical science.Cosmology as a serious scientific study began with the discovery of Einstein's static ...

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Measuring Spacetime: From the Big Bang to Black Holes

Cited by 32 publications

References 83 publications

The angular size–redshift relation in power-law cosmologies

The angular size–redshift relation in power-law cosmologies

Astrophysics in 2002

Issues in the Philosophy of Cosmology

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