The Experts below are selected from a list of 8688 Experts worldwide ranked by ideXlab platform
M Akbar - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic behavior of the Friedmann Equation at the apparent horizon of the frw universe
Physical Review D, 2007Co-Authors: M AkbarAbstract:It is shown that the differential form of Friedmann Equation of a FRW universe can be rewritten as the first law of thermodynamics dE=TdS+WdV at apparent horizon, where E={rho}V is the total energy of matter inside the apparent horizon, V is the volume inside the apparent horizon, W=({rho}-P)/2 is the work density, {rho} and P are energy density and pressure of matter in the universe, respectively. From the thermodynamic identity one can derive that the apparent horizon r-tilde{sub A} has associated entropy S=A/4G and temperature T={kappa}/2{pi} in Einstein general relativity, where A is the area of apparent horizon and {kappa} is the surface gravity at apparent horizon of FRW universe. We extend our procedure to the Gauss-Bonnet gravity and more general Lovelock gravity and show that the differential form of Friedmann Equations in these gravities can also be written as dE=TdS+WdV at the apparent horizon of FRW universe with entropy S being given by expression previously known via black hole thermodynamics.
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thermodynamic behavior of the Friedmann Equation at the apparent horizon of the frw universe
Physical Review D, 2007Co-Authors: M Akbar, Ronggen CaiAbstract:It is shown that the differential form of Friedmann Equation of a FRW universe can be rewritten as the first law of thermodynamics $dE=TdS+WdV$ at apparent horizon, where $E=\ensuremath{\rho}V$ is the total energy of matter inside the apparent horizon, $V$ is the volume inside the apparent horizon, $W=(\ensuremath{\rho}\ensuremath{-}P)/2$ is the work density, $\ensuremath{\rho}$ and $P$ are energy density and pressure of matter in the universe, respectively. From the thermodynamic identity one can derive that the apparent horizon ${\stackrel{\texttildelow{}}{r}}_{A}$ has associated entropy $S=A/4G$ and temperature $T=\ensuremath{\kappa}/2\ensuremath{\pi}$ in Einstein general relativity, where $A$ is the area of apparent horizon and $\ensuremath{\kappa}$ is the surface gravity at apparent horizon of FRW universe. We extend our procedure to the Gauss-Bonnet gravity and more general Lovelock gravity and show that the differential form of Friedmann Equations in these gravities can also be written as $dE=TdS+WdV$ at the apparent horizon of FRW universe with entropy $S$ being given by expression previously known via black hole thermodynamics.
Steven Willison - One of the best experts on this subject based on the ideXlab platform.
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israel conditions for the gauss bonnet theory and the Friedmann Equation on the brane universe
Physics Letters B, 2003Co-Authors: Elias Gravanis, Steven WillisonAbstract:Abstract Assuming an Einstein–Gauss–Bonnet theory of gravitation in a ( D ⩾5)-dimensional spacetime with boundary, we consider the problem of the boundary dynamics given the matter Lagrangian on it. The resulting Equation is applied, in particular, on the derivation of the Friedmann Equation of a 3-brane, understood as the non-orientable boundary of a 5d spacetime. We briefly discuss the contradictory conclusions of the literature.
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israel conditions for the gauss bonnet theory and the Friedmann Equation on the brane universe
arXiv: High Energy Physics - Theory, 2002Co-Authors: Elias Gravanis, Steven WillisonAbstract:Assuming an Einstein-Gauss-Bonnet theory of gravitation in a ($D \geq 5$)-dimensional spacetime with boundary, we consider the problem of the boundary dynamics given the matter Lagrangian on it. The resulting Equation is applied in particular on the derivation of the Friedmann eq. of a 3-brane, understood as the non-orientable boundary of a 5d spacetime. We briefly discuss the contradictory conclusions of the literature.
Tuomas Multamaki - One of the best experts on this subject based on the ideXlab platform.
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cosmic acceleration and extra dimensions constraints on modifications of the Friedmann Equation
Monthly Notices of the Royal Astronomical Society, 2005Co-Authors: O Elgaroy, Tuomas MultamakiAbstract:An alternative to dark energy as an explanation for the present phase of accelerated expansion of the Universe is that the Friedmann Equation is modified, e.g. by extra dimensional gravity, on large scales. We explore a natural parametrization of a general modified Friedmann Equation, and find that the present supernova Type Ia and cosmic microwave background data prefer a correction of the form 1/H to the Friedmann Equation over a cosmological constant.
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cosmic acceleration and extra dimensions constraints on modifications of the Friedmann Equation
arXiv: Astrophysics, 2004Co-Authors: O Elgaroy, Tuomas MultamakiAbstract:An alternative to dark energy as an explanation for the present phase of accelerated expansion of the Universe is that the Friedmann Equation is modified, e.g. by extra dimensional gravity, on large scales. We explore a natural parametrization of a general modified Friedmann Equation, and find that the present supernova type Ia and cosmic microwave background data prefer a correction of the form 1/H over a cosmological constant. We also explore the constraints that can be expected in the future, and find that there are good prospects for distinguishing this model from the standard cosmological constant to very high significance if one combines supernova data with a precise measurement of the matter density.
Yongqiang Wang - One of the best experts on this subject based on the ideXlab platform.
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a note on Friedmann Equation of frw universe in deformed horava lifshitz gravity from entropic force
Communications in Theoretical Physics, 2011Co-Authors: Yongqiang WangAbstract:With entropic interpretation of gravity proposed by Verlinde, we obtain the Friedmann Equation of the Friedmann—Robertson—Walker universe for the deformed Hořava—Lifshitz gravity. It is shown that, when the parameter of Hořava—Lifshitz gravity ω → ∞, the modified Friedmann Equation will go back to the one in Einstein gravity. This results may imply that the entropic interpretation of gravity is effective for the deformed Hořava—Lifshitz gravity.
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a note on Friedmann Equation of frw universe in deformed horava lifshitz gravity from entropic force
Communications in Theoretical Physics, 2011Co-Authors: Shaowen Wei, Yuxiao Liu, Yongqiang WangAbstract:With entropic interpretation of gravity proposed by Verlinde, we obtain the Friedmann Equation of the Friedmann—Robertson—Walker universe for the deformed Hořava—Lifshitz gravity. It is shown that, when the parameter of Hořava—Lifshitz gravity ω → ∞, the modified Friedmann Equation will go back to the one in Einstein gravity. This results may imply that the entropic interpretation of gravity is effective for the deformed Hořava—Lifshitz gravity.
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a note on Friedmann Equation of frw universe in deformed horava lifshitz gravity from entropic force
arXiv: High Energy Physics - Theory, 2010Co-Authors: Shaowen Wei, Yuxiao Liu, Yongqiang WangAbstract:With entropic interpretation of gravity proposed by Verlinde, we obtain the Friedmann Equation of the Friedmann-Robertson-Walker universe for the deformed Ho\v{r}ava-Lifshitz gravity. It is shown that, when the parameter of Ho\v{r}ava-Lifshitz gravity $\omega\rightarrow \infty$, the modified Friedmann Equation will go back to the one in Einstein gravity. This results may imply that the entropic interpretation of gravity is effective for the deformed Ho\v{r}ava-Lifshitz gravity.
Aurelien Barrau - One of the best experts on this subject based on the ideXlab platform.
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modified Friedmann Equation and survey of solutions in effective bianchi i loop quantum cosmology
Classical and Quantum Gravity, 2014Co-Authors: Linda Linsefors, Aurelien BarrauAbstract:In this article, we study the Equations driving the dynamics of a Bianchi-I universe described by holonomy-corrected effective loop quantum cosmology (LQC). We derive the LQC-modified generalized Friedmann Equation, which is used as a guide to find different types of solutions. It turns out that, in this framework, most solutions never reach the classical behavior. Communicated by P R L V Moniz
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modified Friedmann Equation and survey of solutions in effective bianchi i loop quantum cosmology
arXiv: General Relativity and Quantum Cosmology, 2013Co-Authors: Linda Linsefors, Aurelien BarrauAbstract:In this article, we study the Equations driving the dynamics of a Bianchi-I universe described by holonomy corrected effective loop quantum cosmology. We derive the LQC-modified generalized Friedmann Equation, which is used as a guide to find different types of solutions. It turns out that, in this framework, most solutions never reach the classical behavior.
