The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
A. V. Timoshkin - One of the best experts on this subject based on the ideXlab platform.
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Quasi-Rip universe induced by the fluid with Inhomogeneous Equation of state
arXiv: General Relativity and Quantum Cosmology, 2013Co-Authors: Iver Brevik, V. V. Obukhov, A. V. TimoshkinAbstract:We investigate a specific model for dark energy, which lead to the Quasi-Rip cosmology. In the Quasi-Rip model, the Equation of the state parameter $w$ is less than -1 in the first stage, but then in the second stage is larger than -1. The conditions for the appearance the Quasi-Rip in the terms of the parameters Equation of state are received.
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Quasi-Rip and Pseudo-Rip universes induced by the fluid Inhomogeneous Equation of state
Astrophysics and Space Science, 2012Co-Authors: Iver Brevik, V. V. Obukhov, A. V. TimoshkinAbstract:We investigate specific models for a dark energy universe leading to Quasi-Rip and Pseudo-Rip cosmologies. In the Quasi-Rip model the Equation of state parameter w is less than −1 in the first stage, but becomes larger than −1 in the second stage. In the Pseudo-Rip model the Hubble parameter tends to a constant value in the remote future, although w is always less than −1. Conditions for the appearance of the Quasi-Rip and the Pseudo-Rip in terms of the parameters in the Equation of state are determined. Analogies with the theory of viscous cosmology are discussed.
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Dark energy with time-dependent Equation of state
arXiv: General Relativity and Quantum Cosmology, 2009Co-Authors: O. G. Gorbunova, A. V. TimoshkinAbstract:The accelerating Friedmann flat universe, filled with an ideal fluid with a linear (oscillating) Inhomogeneous Equation of state (EoS) depending on time, is reviewed. The Equations of motions are solved. It is shown that in some cases there appears a quasi-periodic universe, which repeats the cycles of phantom-type space acceleration.
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Accelerated expansion of the Friedmann Universe filled with ideal liquid described by an Inhomogeneous Equation of state
Russian Physics Journal, 2007Co-Authors: Iver Brevik, O. G. Gorbunova, A. V. TimoshkinAbstract:A spatially flat Friedmann Universe filled with ideal liquid described by a time-dependent linear Inhomogeneous Equation of state is considered. The gravitational Equation of motion is solved. It is shown that in certain cases, a quasi-periodic Universe results repeating the cycles of space acceleration of the phantom (non-phantom) type. The occurrence of future singularities for a number of parameter values is pointed out.
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A FRW dark fluid with a non-linear Inhomogeneous Equation of state
European Physical Journal C, 2007Co-Authors: Iver Brevik, O. G. Gorbunova, Emilio Elizalde, A. V. TimoshkinAbstract:A dark Friedman–Robertson–Walker fluid governed by a non-linear Inhomogeneous Equation of state is considered that can be viewed as a conveniently simple paradigm for a whole class of models that exhibit phase transitions from a non-phantom towards a phantom era (superacceleration transition). On the other hand, such dark fluid models may also describe quintessence-like cosmic acceleration. Thermodynamical considerations for the processes involved, which are of great importance in the characterization of the global evolution of the corresponding universe, are given too. Connecting the proposed Equation of state with an anisotropic Kasner universe with viscosity, we are led to the plausible conjecture of a dark fluid origin of the anisotropies in the early universe.
A. V. Aksenov - One of the best experts on this subject based on the ideXlab platform.
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Symmetries and Fundamental Solutions of Displacement Equations for a Transversely Isotropic Elastic Medium
Understanding Complex Systems, 2018Co-Authors: A. V. AksenovAbstract:A fourth-order linear elliptic partial differential Equation describing the displacements of a transversely isotropic linear elastic medium is considered. Its symmetries and the symmetries of an Inhomogeneous Equation with a delta function on the right-hand side are found. The latter symmetries are used to construct an invariant fundamental solution of the original Equation in terms of elementary functions.
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Fundamental solution of the elasticity theory Equations in displacements for a transversely isotropic medium
Differential Equations, 2017Co-Authors: A. V. AksenovAbstract:We consider a linear fourth-order elliptic partial differential Equation describing the displacements of a transversely isotropic linearly elastic medium. We find the symmetries of this Equation and of the Inhomogeneous Equation with the delta function on the right-hand side. Based on the symmetries of the Inhomogeneous Equation, we construct an invariant fundamental solution in elementary functions.
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Fundamental solution of displacement Equations for a transversely isotropic elastic medium
Doklady Mathematics, 2016Co-Authors: A. V. AksenovAbstract:A fourth-order linear elliptic partial differential Equation describing the displacements of a transversely isotropic linear elastic medium is considered. Its symmetries and the symmetries of an Inhomogeneous Equation with a delta function on the right-hand side are found. The latter symmetries are used to construct an invariant fundamental solution of the original Equation in terms of elementary functions.
Ivan Veselic - One of the best experts on this subject based on the ideXlab platform.
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exhaustion approximation for the control problem of the heat or schrodinger semigroup on unbounded domains
Archiv der Mathematik, 2020Co-Authors: Albrecht Seelmann, Ivan VeselicAbstract:We consider the control problem of the heat Equation on bounded and unbounded domains, and more generally the corresponding Inhomogeneous Equation for the Schrodinger semigroup. We show that if the sequence of null-controls associated to an exhaustion of an unbounded domain converges, then the solutions do in the same way, and that the control cost estimate carries over to the limiting problem on the unbounded domain. This allows to infer the controllability on unbounded domains by studying the control problem on a sequence of bounded domains.
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exhaustion approximation for the control problem of the heat or schr odinger semigroup on unbounded domains
arXiv: Optimization and Control, 2018Co-Authors: Albrecht Seelmann, Ivan VeselicAbstract:We consider the control problem of the heat Equation on bounded and unbounded domains, and more generally the corresponding Inhomogeneous Equation for the Schr\"odinger semigroup. We show that if the sequence of null-controls associated to an exhaustion of an unbounded domain converges, then the solutions do in the same way, and that the control cost estimate carries over to the limiting problem on the unbounded domain. This allows to infer the controllability on unbounded domains by studying the control problem on a sequence of bounded domains.
Rui Yu - One of the best experts on this subject based on the ideXlab platform.
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deformed soliton breather and rogue wave solutions of an Inhomogeneous nonlinear hirota Equation
Communications in Nonlinear Science and Numerical Simulation, 2015Co-Authors: Xuelin Yong, Yehui Huang, Rui YuAbstract:Abstract In this paper, an Inhomogeneous nonlinear Hirota Equation with linear Inhomogeneous coefficient and higher-order dispersion is investigated in detail. In describing wave propagation in the ocean and optical fibers, it can be viewed as an approximation which is more accurate than the nonlinear Schr o ¨ dinger Equation. Firstly, we modified the Darboux transformation technique to show how to construct solutions of this Inhomogeneous Equation which owns a non-isospectral Lax pair. Furthermore, the deformed soliton, breather and rogue wave solutions of this Equation are studied via the Darboux transformation method, respectively. Finally, properties of those solutions in the Inhomogeneous media are discussed to illustrate the influences of variable coefficients.
Iver Brevik - One of the best experts on this subject based on the ideXlab platform.
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Quasi-Rip universe induced by the fluid with Inhomogeneous Equation of state
arXiv: General Relativity and Quantum Cosmology, 2013Co-Authors: Iver Brevik, V. V. Obukhov, A. V. TimoshkinAbstract:We investigate a specific model for dark energy, which lead to the Quasi-Rip cosmology. In the Quasi-Rip model, the Equation of the state parameter $w$ is less than -1 in the first stage, but then in the second stage is larger than -1. The conditions for the appearance the Quasi-Rip in the terms of the parameters Equation of state are received.
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Quasi-Rip and Pseudo-Rip universes induced by the fluid Inhomogeneous Equation of state
Astrophysics and Space Science, 2012Co-Authors: Iver Brevik, V. V. Obukhov, A. V. TimoshkinAbstract:We investigate specific models for a dark energy universe leading to Quasi-Rip and Pseudo-Rip cosmologies. In the Quasi-Rip model the Equation of state parameter w is less than −1 in the first stage, but becomes larger than −1 in the second stage. In the Pseudo-Rip model the Hubble parameter tends to a constant value in the remote future, although w is always less than −1. Conditions for the appearance of the Quasi-Rip and the Pseudo-Rip in terms of the parameters in the Equation of state are determined. Analogies with the theory of viscous cosmology are discussed.
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Accelerated expansion of the Friedmann Universe filled with ideal liquid described by an Inhomogeneous Equation of state
Russian Physics Journal, 2007Co-Authors: Iver Brevik, O. G. Gorbunova, A. V. TimoshkinAbstract:A spatially flat Friedmann Universe filled with ideal liquid described by a time-dependent linear Inhomogeneous Equation of state is considered. The gravitational Equation of motion is solved. It is shown that in certain cases, a quasi-periodic Universe results repeating the cycles of space acceleration of the phantom (non-phantom) type. The occurrence of future singularities for a number of parameter values is pointed out.
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A FRW dark fluid with a non-linear Inhomogeneous Equation of state
European Physical Journal C, 2007Co-Authors: Iver Brevik, O. G. Gorbunova, Emilio Elizalde, A. V. TimoshkinAbstract:A dark Friedman–Robertson–Walker fluid governed by a non-linear Inhomogeneous Equation of state is considered that can be viewed as a conveniently simple paradigm for a whole class of models that exhibit phase transitions from a non-phantom towards a phantom era (superacceleration transition). On the other hand, such dark fluid models may also describe quintessence-like cosmic acceleration. Thermodynamical considerations for the processes involved, which are of great importance in the characterization of the global evolution of the corresponding universe, are given too. Connecting the proposed Equation of state with an anisotropic Kasner universe with viscosity, we are led to the plausible conjecture of a dark fluid origin of the anisotropies in the early universe.
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Dark energy fluid with time-dependent, Inhomogeneous Equation of state
European Physical Journal C, 2007Co-Authors: Iver Brevik, O. G. Gorbunova, A. V. TimoshkinAbstract:The four-dimensional flat Friedman universe filled with an ideal fluid with a linear (oscillating) Inhomogeneous Equation of state (EoS) depending on time is studied. The Equations of motion are solved. It is shown that in some cases there appears a quasi-periodical universe that repeats the cycles of phantom-type space acceleration. The appearance of future singularities resulting from various choices for the input parameters is discussed.