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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 article, the authors considered the magnetic universe in non-linear electrodynamics and discussed the validity of the generalized second law of thermodynamics of magnetic universe bounded by Hubble, apparent, particle and event horizons.
22 citations
TL;DR: In this article, a model of a stationary universe is proposed, where time is defined as a local and quantum-mechanical notion in the sense that it is defined for each local and QM system consisting of finite number of particles.
Abstract: A model of a stationary universe is proposed. In this framework, time is defined as a local and quantum-mechanical notion in the sense that it is defined for each local and quantum-mechanical system consisting of finite number of particles. The total universe consisting of infinite number of particles has no time associated. It is a stationary bound state of the total Hamiltonian of infinite degrees of freedom. The quantum mechanics and the theory of general relativity are consistently united in this context if one uses this notion of local and quantum-mechanical time. As one of the consequences, the Einstein-Podolsky-Rosen paradox is resolved. The Hubble red-shift is explained as a consequence of general relativity which is consistent with quantum mechanics. This does not require us to argue on the beginning nor the end of the universe. The universe just exists without time.
22 citations
TL;DR: In this paper, a general-relativistic model of cosmological expansion dominated by a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the deceleration parameter, and the age of the universe.
Abstract: The Proca generalization of electrodynamics admits the possibility that the universe could possess a net electric charge uniformly distributed throughout space, while possessing no electric field. A general-relativistic model of cosmological expansion dominated by such a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the deceleration parameter, and the age of the universe. However, if this cosmology applied at the present epoch, the very early expansion of the universe would have been too rapid for cosmological nucleosynthesis or thermalization of the background radiation to have occurred. Hence, domination of the present expansion by background charge appears to be incompatible with the 3-K background and big-bang production of light elements. If the present background charge density were sufficiently small (but not strictly zero), expansion from the epoch of nucleosynthesis would proceed according to the conventional scenario, but the energy due to the background charge would have dominated at some earlier epoch. This last possibility leads to equality of pressure and energy density in the primordial universe.
22 citations
TL;DR: In this paper, a stability criterion is derived in general relativity for self-similar solutions with a scalar field and those with a stiff fluid, which is a perfect fluid with the equation of state $P=\rho.
Abstract: A stability criterion is derived in general relativity for self-similar solutions with a scalar field and those with a stiff fluid, which is a perfect fluid with the equation of state $P=\rho$. A wide class of self-similar solutions turn out to be unstable against kink mode perturbation. According to the criterion, the Evans-Coleman stiff-fluid solution is unstable and cannot be a critical solution for the spherical collapse of a stiff fluid if we allow sufficiently small discontinuity in the density gradient field in the initial data sets. The self-similar scalar-field solution, which was recently found numerically by Brady {\it et al.} (2002 {\it Class. Quantum. Grav.} {\bf 19} 6359), is also unstable. Both the flat Friedmann universe with a scalar field and that with a stiff fluid suffer from kink instability at the particle horizon scale.
22 citations
TL;DR: Using the grand unified theories, the authors of as discussed by the authors extrapolate cosmic events into a future that is up to 10/sup 100/times the current age of the universe. But the authors do not specify whether the universe is closed or open.
Abstract: Using the grand unified theories, the authors extrapolate cosmic events into a future that is up to 10/sup 100/ times the current age of the universe. The framework for the calculations about the remote future is the big-bang model. From the standpoint of cosmology the importance of the extrapolations is that the grand unified theories have consequences that can be tested in terrestial laboratories, and so the predictions they make under extreme conditions can be confirmed. Since it is not know if the universe is closed or open, the authors give a future for each type universe. The main events for an open universe are: (1) stars will run out of fuel; (2) stars will lose their planets; (3) galactic evaporation; (4) proton decay; (5) decay of black holes. For a closed universe the expansion phase follows the same events as that of the open universe. It is possible that if the universe is closed, it could be cyclic. (SC)
22 citations