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Particle horizon

About: Particle horizon is a research topic. Over the lifetime, 2096 publications have been published within this topic receiving 69137 citations.


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TL;DR: In this paper, the velocity of light and the expansion of the universe are two aspects of one single concept connecting space and time in the expanding universe, and it is shown that solving Friedman's equations with that interpretation (keeping c = constant) could explain number of unnatural features of the standard cosmology.
Abstract: We make the hypothesis that the velocity of light and the expansion of the universe are two aspects of one single concept connecting space and time in the expanding universe. We show that solving Friedman’s equations with that interpretation (keeping c = constant) could explain number of unnatural features of the standard cosmology. We thus examine in that light the flatness problem, the problem of the observed uniformity in term of temperature and density of the cosmological background radiation and the small-scale inhomogeneity problem. We finally show that using this interpretation of c leads to reconsider the Hubble diagram of distance moduli and redshifts as obtained from recent observations of type Ia supernovae without having to need an accelerating universe.

8 citations

Journal ArticleDOI
TL;DR: In this article, the group velocity of gravitational waves in a flat Friedman-Robertson-Walker universe is investigated, and it is shown that for plane waves with wavelength well inside the horizon, and a universe filled with an ideal fluid with the pressure to density ratio less than 1/3, group velocity is greater than the velocity of light.
Abstract: The group velocity of gravitational waves in a flat Friedman–Robertson–Walker universe is investigated. For plane waves with wavelength well inside the horizon, and a universe filled with an ideal fluid with the pressure to density ratio less than 1/3, the group velocity is greater than the velocity of light. As a result, a planar pulse of gravitational waves propagating through the universe during the matter/dark energy dominated era arrives to the observer with the peak shifted towards the forefront. For gravitational waves emitted by inspiralling supermassive black holes at the edge of the observable universe, the typical shift that remains after the effects of nonplanarity are suppressed is of order of 10 ps.

8 citations

Journal ArticleDOI
TL;DR: The f(T) theory is an extension of Teleparallel theory of gravity, where T is the torsion scalar as discussed by the authors, which is used to explain the present cosmic accelerating expansion of the universe.
Abstract: The f(T) theory is recently proposed to explain the present cosmic accelerating expansion of the universe. f(T) theory is an extension of Teleparallel theory of gravity, where T is the torsion scalar. This paper contains the construction of f(T) models within the Kantowski-Sachs universe. For this purpose, we use conservation equation and equation of state parameter, which represents the different phases of the universe. We discuss possible cases for the matter dominated era, radiation dominated era, present dark energy phase and their combinations. Particularly, a constant solution has been obtained which may correspond to the cosmological constant. Further, we consider two well known f(T) models and derive the equation of state parameter and discuss the cosmic acceleration. Also, the Hubble parameter and average scale factor have been evaluated.

8 citations

Journal ArticleDOI
TL;DR: In this paper, exact analytical expressions for dilaton field σ, cosmological radiusR and density parameter Ω are obtained fork=+1,0,−1 universe in the radiation-dominated epoch.
Abstract: We use the generalized Brans-Dicke theory, in which the Pauli metric is identified to be the physical space-time metric, to study the Universe in different epochs. Exact analytical expressions for dilaton field σ, cosmological radiusR and density parameter Ω are obtained fork=+1,0,−1 Universe in the radiation-dominated epoch. For matter dominated Epoch, exact analytical expressions for Hubble parameterH, cosmological radius, dilaton field, deceleration factorq, density parameter and the gravitational coupling of the ordinary matter are obtained for the flat Universe. Other important results are: (1) the density parameter Ω is always less than unity for the flat Universe because the dilaton field plays a role as an effective dark matter, and (2) the new Brans-Dicke parameter Ω must be larger than 31.75 in order to consistent with the observed data.

8 citations

Posted Content
TL;DR: The Local Universe is the most detail studied part of the observable region of space with the radius R about 100 Mpc and there are two empirical fundamental cosmological laws directly established from observations in the Local Universe independently from cosmology theory.
Abstract: The Local Universe is the most detail studied part of the observable region of space with the radius R about 100 Mpc. There are two empirical fundamental cosmological laws directly established from observations in the Local Universe independently from cosmological theory: first, the Hubble-Humason-Sandage linear redshift-distance law and second, Carpenter- Karachentsev-deVaucouleurs density-radius power-law. Review of modern state of these empirical laws and their cosmological significance is given. Possible theoretical interpretations of the surprising coexistence of both laws at the spatial scales from 1 Mpc to 100 Mpc are discussed. Comparison of the standard space-expansion explanation of the cosmological redshift with possible global gravitational redshift model is given

7 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202320
202247
20216
202010
201910
201814