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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, an interaction horizon is introduced that allows this scale to be determined for Robertson-Walker models for homogeneous isotropic universes, where the particle horizon defines causally connected regions.
Abstract: In homogeneous isotropic universes the particle horizon defines causally connected regions. For inflationary universes it is known that microphysics can interact coherently only on a much smaller scale. An interaction horizon is introduced that allows this scale to be determined for Robertson-Walker models. During inflation its upper bound is the event horizon.
2 citations
01 Jan 2002
TL;DR: In this paper, the authors discuss the topology of the big bang and the horizon structure of inflationary universes, and introduce the standard Friedman models of the Big Bang and its evolution.
Abstract: After a general introduction to the standard Friedman models we discuss the topology of the big bang and the horizon structure of inflationary universes.
2 citations
01 Jan 2008
TL;DR: In this article, a Bianchi type I massive string cosmological model in the presence of a magnetic field is investigated and exact solutions are produced using a few tractable assumptions usually accepted in the literature.
Abstract: A Bianchi type I massive string cosmological model in the presence of a magnetic field is investigated. Some exact solutions are produced using a few tractable assumptions usually accepted in the literature. The analytical solutions are supplemented with numerical computations. In the frame of the present model the evolution of the Universe and other physical aspects are discussed. Since the observation of the current expansion of the Universe which has apparently accelerated in the recent past, the anomalies found in the cosmic microwave background (CMB) and the large structures observations it becomes obvious that a pure Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology should be amended. Bianchi type I (BI) cosmological models are the simplest anisotropic Universe models playing an important role in understanding essential features of the Universe. I n this class of models it is possible to accommodate the presence of cosmic strings as an example of an anisotropy of space-times generated by one dimensional topological defects. In the last time cosmic strings have drawn considerable interest among the researchers for various aspects such as the study of the early Universe. The presence of cosmic strings in the early Universe could be explained using grand unified theories. These strings arise during the phase transition after the Big Bang explosion as the temperature goes down below some critical critical point. It is believed that the existence of strings in the early Universe gives rise to the density fluctuations whi ch leads to the formation of the galaxies. Also the cosmic strings have been used in attempts to investigate anisotropic dark energy component including a coupling between dark energy and a perfect fluid (dark matter ) (1). The cosmic string has stress energy and it is couple to the gravitational field. In what follows we shall investigate the evolution of a BI cosmological models in presence of a cosmic string and magnetic fluid (2). The inclusion of the magnetic fi eld is motivated by the observational cosmology and astrophysics indicating that many subsystems of the Universe possess magnetic fields (see e. g. the reviews (3, 4) and references therein). The paper has the following structure. We shall review the basic equations of an anisotropic BI model in the presence of a system of cosmic string and magnetic field . In Section III we introduce a few plausible assumptions usually accepted in the literature and some exact solutions are produced. We present also some numerical results regarding the evolution of the Universe in the presence or absence of a magnetic string. At the end we shall summarize the results and outline future prospects. 2 Fundamental Equations and general solutions The line element of a BI Universe is ds 2 = (dt) 2 − a1(t) 2 (dx 1 ) 2 − a2(t) 2 (dx 2 ) 2 − a3(t) 2 (dx 3 ) 2 .
2 citations
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TL;DR: In this paper, the authors investigated the apparent horizons according to the distribution of cosmic matter and derived the Hawking temperature near the apparent cosmological horizon with a proper definition of the Kodama vector.
Abstract: Recently we solved the Einstein's field equations to obtain the exact solution of the cosmological model with the Morris-Thorne type wormhole. We found the apparent horizons and analyzed their geometric natures, including the causal tructures. We also derived the Hawking temperature near the apparent cosmological horizon with a proper definition of the Kodama vector.
In this paper, we investigate the dynamic properties of the apparent horizons according to the distribution of cosmic matter. The matter-, radiation-, and lambda-dominated universes are considered as a single component universe. As a multi-component universe, we adopt the $\Lambda$CDM universe which contains the matter and lambda. We also considered the speeds of apparent horizons and compared them with those of the universe without wormhole.
The past light cone and the particle horizon is examined for what happens in the case of model with wormhole. Since the spatial coordinates of the spacetime with the wormhole are limited outside the throat, the past light cone can be operated by removing the smaller-than-wormhole region. The past light cones without wormhole begin start earlier than the past light cones with wormhole in conformal time-proper distance coordinates. The travel-through-wormhole can shows different part from normal one. Therefore, the particle horizon distance determined from the observer's past light cone can not be defined in a unique way. The case of the travel-through-wormhole can be extended into another universe or far distant causally disconnected region.
2 citations
TL;DR: In this article, the maximum volume of the closed Friedmann closed universe in expansion was shown to be 2π2R3(t), instead of π2R 3(t) as found previously.
Abstract: The maximum volume of the closed Friedmann universe is further investigated and is shown to be 2π2R3(t), instead of π2R3(t) as found previously. This discrepancy comes from the incomplete use of the volume formula of 3-dimensional spherical space in the astronomical literature. Mathematically, there exists the maximum volume at any cosmic timet in a 3-dimensional spherical case. However, the Friedmann closed universe in expansion reaches its maximum volume only at the timet m of the maximum scale factorR(t m ). The particle horizon has no limitation for the farthest objects in the closed Friedmann universe if the proper distance of objects is compared with the particle horizon as it should be. It will lead to absurdity if the luminosity distance of objects is compared with the proper distance of the particle horizon.
2 citations