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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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01 Jan 2000
TL;DR: The origin of the universe was discussed in this paper, where it was estimated that all matter and energy originated from a single location in the Big Bang about 20 billion years ago, and the universe may keep expanding or the expansion may give way to arrest or even contraction.
Abstract: This chapter discusses origin of the universe. In Newton's time, the universe was pictured as an infinite sea of stars in fixed positions. The only movements that astronomers were aware of were those of the planets about the sun and satellites about the planets. Newton argued that the stars were scattered across an infinite expanse of space in more or less fixed positions. In proposing this model for the universe, Newton's attention was focused on the balance of gravitational forces. Einstein's theory of relativity changed our thinking about space and time, but even Einstein did not reject the concept of an infinite static universe despite the inconsistency of this model with his own theory. Hubble's model for the universe was the outcome of research that permitted him to estimate the movement of the stars relative to the Earth. The main way in which such studies are made is by analyzing the light they emit, the distance of different galaxies, and the speed with which they are moving relative to one another. It has been estimated that all matter and energy originated from a single location in the Big Bang about 20 billion years ago. The universe may keep expanding or the expansion may give way to arrest or even contraction. Current indications from measured recessional velocities of very distant supernovas favor the notion of indefinite expansion.
Posted Content
TL;DR: In this paper, a connection between matter and cosmological constant Lambda via the Newtonian cosmic potential of the matter within the expanding particle horizon was considered, which suggests that the cosmic potential, while subject to the expansion of space, always yields a constant background potential.
Abstract: We consider a possible connection between matter and cosmological constant $\Lambda$ via the Newtonian cosmic potential of the matter within the expanding particle horizon. Consistent with GR, an increasing potential may drive the metric expansion of space. Cosmic recession of mass must, in turn, affect the potential in an opposite sense. Independent of this, several considerations point at $-\tfrac{1}{2}c^{2}$ as the representation of the background potential in the various GR metrics. This suggests that the cosmic potential, while subject to the expansion of space, always yields a constant background potential $-\tfrac{1}{2}c^{2}$. Analysis of this 'redshift' of the cosmic potential yields for perfect fluids the exact same solutions of the scale factor as the standard Friedmann equations, including an accelerating de Sitter universe. Though counter intuitive at first sight, gravity may drive cosmic acceleration.
Posted Content
TL;DR: A stationary line element of general relativity seems to be compatible to essential cosmological facts as discussed by the authors, though only as far as one can expect solving the nonlinear Einstein equations neglecting local cosmic evolution and all spatial inhomogeneities as well.
Abstract: A stationary line element of general relativity seems to be compatible to essential cosmological facts (though only as far as one can expect solving the nonlinear Einstein equations neglecting local cosmic evolution and all spatial inhomogeneities as well). There is a preferred spatially Euclidean cosmic reference frame where the extra-galactic speed of light is constant c* = c, and the galaxies are statistically at rest. Spectral rods and atomic clocks, however, do not indicate this cosmic space and this cosmic time. The solutions put up here for discussion are suitable to avoid serious difficulties in physics such as a beginning of the universe as a whole or the necessity of continuous creation of matter or an empty universe with a cosmological constant but no matter at all. Especially from the stationary line element, it follows a negative cosmic gravitational pressure of one third the critical energy density. In addition, there is an average baryonic radiation density equivalent to a black body radiation of approximately 3 K. The resulting increase of the time rate of natural clocks in comparison with cosmic time is a simple explanation for the redshift of starlight. This redshift turns out to be independent of time, thus indicating a stationary universe.
01 Jun 1997
TL;DR: In this paper, it was shown that the observable universe is not self-shielded for most of its existence and does not possess an optical depth of unity, since the mass of the proton is much larger than that of the electron, and the nonbaryonic dark matter does not affect the optical depth.
Abstract: Summary. — Because the mass of the proton is much larger than the mass of theelectron, and the non-baryonic dark matter does not affect the optical depth, theobservable universe is not self-shielded, i.e. does not possess an optical depth of unity.PACS 98.80.Dr – Theoretical cosmology. It was recently suggested [1] that the observable universe could be self-shielded forelectromagnetic radiation. This assertion was based on the remark that by postulatinga self-shielded, flat universe, containing only one type of particle of charge equal to theelementary charge e , a characteristic mass m 0 4( He 4 / Gc 3 ) 1/3 of the order of theelectron mass emerges, where H is the Hubble constant, G is the gravitationalconstant, and c is the speed of light.The objective of this note is to demonstrate that the universe is not and was notself-shielded for most of its existence. The quantities of interest are: the optical depth t , the critical density r c , the density parameterV, the number density of particles
Posted Content
TL;DR: In this paper, the process of formation of the universe with its further expansion in the first evolution stage is investigated in the framework of Friedmann-Robertson-Walker metrics on the basis of quantum model, where a new type of matter is introduced, which energy density is dependent on velocity of the expansion.
Abstract: Process of formation of the universe with its further expansion in the first evolution stage is investigated in the framework of Friedmann-Robertson-Walker metrics on the basis of quantum model, where a new type of matter is introduced, which energy density is dependent on velocity of the expansion. It is shown that such an improvement of the model forms potential barrier for the flat universe at $k=0$ (in contrast with generalized Chaplygin gas model). Peculiarities of wave function are analyzed in details, which is calculated by fully quantum (non-semiclassic) approach, for the different barrier regions and stages of evolution. Resonant influence of the initial and boundary conditions on the barrier penetrability is shown (in contrast with Vilenkin and Hawking approaches). In order to perform a comparative analysis, how much quickly the universe is expanded by different models, new quantum definitions of velocity and Hubble function are introduced. These notions allow us to study dynamics of evolution of universe in quantum cosmology both in the first stage, and in later times.

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