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Hiromi Saida - One of the best experts on this subject based on the ideXlab platform.
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Black Hole Evaporation as a Nonequilibrium Process
arXiv: General Relativity and Quantum Cosmology, 2008Co-Authors: Hiromi SaidaAbstract:When a black hole evaporates, there arises a net energy flow from the black hole into its outside environment due to the Hawking radiation and the energy accretion onto black hole. Exactly speaking, due to the net energy flow, the black hole evaporation is a Nonequilibrium Process. To study details of evaporation Process, Nonequilibrium effects of the net energy flow should be taken into account. In this article we simplify the situation so that the Hawking radiation consists of non-self-interacting massless matter fields and also the energy accretion onto the black hole consists of the same fields. Then we find that the Nonequilibrium nature of black hole evaporation is described by a Nonequilibrium state of that field, and we formulate Nonequilibrium thermodynamics of non-self-interacting massless fields. By applying it to black hole evaporation, followings are shown: (1) Nonequilibrium effects of the energy flow tends to accelerate the black hole evaporation, and, consequently, a specific Nonequilibrium phenomenon of semi-classical black hole evaporation is suggested. Furthermore a suggestion about the end state of quantum size black hole evaporation is proposed in the context of information loss paradox. (2) Negative heat capacity of black hole is the physical essence of the generalized second law of black hole thermodynamics, and self-entropy production inside the matter around black hole is not necessary to ensure the generalized second law. Furthermore a lower bound for total entropy at the end of black hole evaporation is given. A relation of the lower bound with the so-called covariant entropy bound conjecture is interesting but left as an open issue.
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black hole evaporation in a heat bath as a Nonequilibrium Process and its final fate
Classical and Quantum Gravity, 2007Co-Authors: Hiromi SaidaAbstract:We consider a black hole in a heat bath, and the whole system which consists of the black hole and the heat bath is isolated from outside environments. When the black hole evaporates, the Hawking radiation causes an energy flow from the black hole to the heat bath. Therefore, since no energy flow arises in an equilibrium state, the thermodynamic state of the whole system is not in equilibrium. That is, in a region around the black hole, the matter field of Hawking radiation and that of heat bath should be in a Nonequilibrium state due to the energy flow. Using a simple model which reflects the Nonequilibrium nature of energy flow, we find the Nonequilibrium effect on a black hole evaporation as follows: if the Nonequilibrium region around a black hole is not so large, the evaporation time scale of a black hole in a heat bath becomes longer than that in an empty space (a situation without heat bath), because of the incoming energy flow from the heat bath to the black hole. However, if the Nonequilibrium region around a black hole is sufficiently large, the evaporation time scale in a heat bath becomes shorter than that in an empty space, because a Nonequilibrium effect of the temperature difference between the black hole and heat bath appears as a strong energy extraction from the black hole by the heat bath. Further, a specific Nonequilibrium phenomenon is found: a quasi-equilibrium evaporation stage under the Nonequilibrium effect proceeds abruptly to a quantum evaporation stage at a semi-classical level (at black hole radius Rg > Planck length) within a very short time scale with a strong burst of energy. (Contrarily, when the Nonequilibrium effect is not taken into account, a quasi-equilibrium stage proceeds smoothly to a quantum stage at Rg < Planck length without so strong an energy burst.) That is, the Nonequilibrium effect of energy flow tends to make a black hole evaporation Process more dynamical and to accelerate that Process. Finally, on the final fate of black hole evaporation, we find that, in order to make the total entropy of the whole system increase along an evaporation Process, a remnant should remain after the evaporation of black hole without respect to the size of the Nonequilibrium region around the black hole. This implies that the information loss problem may disappear due to the Nonequilibrium effect of energy flow.
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black hole evaporation in a heat bath as a Nonequilibrium Process and its final fate
arXiv: General Relativity and Quantum Cosmology, 2007Co-Authors: Hiromi SaidaAbstract:When a black hole evaporates, there arises a net energy flow from black hole into its outside environment (heat bath). The existence of energy flow means that the thermodynamic state of the whole system, which consists of the black hole and the heat bath, is in a Nonequilibrium state. Therefore, in order to study the detail of evaporation Process, the Nonequilibrium effects of the energy flow should be taken into account. Using the Nonequilibrium thermodynamics which has been formulated recently, this paper shows the following: (1) Time scale of black hole evaporation in a heat bath becomes shorter than that of the evaporation in an empty space (a situation without heat bath), because a Nonequilibrium effect of temperature difference between the black hole and heat bath appears as a strong energy extraction from the black hole by the heat bath. (2) Consequently a huge energy burst (stronger than that of the evaporation in an empty space) arises at the end of semi-classical stage of evaporation. (3) It is suggested that a remnant of Planck size remains after the quantum stage of evaporation in order to guarantee the increase of total entropy of the whole system.
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the generalized second law and the black hole evaporation in an empty space as a Nonequilibrium Process
Classical and Quantum Gravity, 2006Co-Authors: Hiromi SaidaAbstract:When a black hole is in an empty space in which there is no matter field except that of the Hawking radiation (Hawking field), then the black hole evaporates and the entropy of the black hole decreases. The generalized second law guarantees the increase of the total entropy of the whole system which consists of the black hole and the Hawking field. That is, the increase of the entropy of the Hawking field is faster than the decrease of the black hole entropy. In a naive sense, one may expect that the entropy increase of the Hawking field is due to the self-interaction among the composite particles of the Hawking field, and that the self-relaxation of the Hawking field results in the entropy increase. Then, when one considers a non-self-interacting matter field as the Hawking field, it is obvious that self-relaxation does not take place, and one may think that the total entropy does not increase. However, using Nonequilibrium thermodynamics which has been developed recently, we find for the non-self-interacting Hawking field that the rate of entropy increase of the Hawking field (the entropy emission rate by the black hole) grows faster than the rate of entropy decrease of the black hole during the black hole evaporation in empty space. The origin of the entropy increase of the Hawking field is the increase of the black hole temperature. Hence an understanding of the generalized second law in the context of Nonequilibrium thermodynamics is suggested; even if the self-relaxation of the Hawking field does not take place, the temperature increase of the black hole during the evaporation Process causes the entropy increase of the Hawking field to result in the increase of the total entropy.
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the generalised second law and the black hole evaporation in an empty space as a Nonequilibrium Process
arXiv: General Relativity and Quantum Cosmology, 2006Co-Authors: Hiromi SaidaAbstract:When a black hole is in an empty space on which there is no matter field except that of the Hawking radiation (Hawking field), then the black hole evaporates and the entropy of the black hole decreases. The generalised second law guarantees the increase of the total entropy of the whole system which consists of the black hole and the Hawking field. That is, the increase of the entropy of the Hawking field is faster than the decrease of the black hole entropy. In naive sense, one may expect that the entropy increase of the Hawking field is due to the self-interaction among the composite particles of the Hawking field, and that the "self"-relaxation of the Hawking field results in the entropy increase. Then, when one consider a non-self-interacting matter field as the Hawking field, it is obvious that the self-relaxation does not take place, and one may think that the total entropy does not increase. However, using Nonequilibrium thermodynamics which has been developed recently, we find for the non-self-interacting Hawking field that the rate of entropy increase of the Hawking field (the entropy emission rate by the black hole) grows faster than the rate of entropy decrease of the black hole along the black hole evaporation in the empty space. The origin of the entropy increase of the Hawking field is the increase of the black hole temperature. Hence an understanding of the generalised second law in the context of the Nonequilibrium thermodynamics is suggested; even if the self-relaxation of the Hawking field does not take place, the temperature increase of the black hole during the evaporation Process causes the entropy increase of the Hawking field to result in the increase of the total entropy.
Yang Shen - One of the best experts on this subject based on the ideXlab platform.
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high throughput phase field design of high energy density polymer nanocomposites
Advanced Materials, 2018Co-Authors: Yuanhua Lin, Cewen Nan, Zhong Hui Shen, Jianjun Wang, Longqing Chen, Yang ShenAbstract:Understanding the dielectric breakdown behavior of polymer nanocomposites is crucial to the design of high-energy-density dielectric materials with reliable performances. It is however challenging to predict the breakdown behavior due to the complicated factors involved in this highly Nonequilibrium Process. In this work, a comprehensive phase-field model is developed to investigate the breakdown behavior of polymer nanocomposites under electrostatic stimuli. It is found that the breakdown strength and path significantly depend on the microstructure of the nanocomposite. The predicted breakdown strengths for polymer nanocomposites with specific microstructures agree with existing experimental measurements. Using this phase-field model, a high throughput calculation is performed to seek the optimal microstructure. Based on the high-throughput calculation, a sandwich microstructure for PVDF-BaTiO3 nanocomposite is designed, where the upper and lower layers are filled with parallel nanosheets and the middle layer is filled with vertical nanofibers. It has an enhanced energy density of 2.44 times that of the pure PVDF polymer. The present work provides a computational approach for understanding the electrostatic breakdown, and it is expected to stimulate future experimental efforts on synthesizing polymer nanocomposites with novel microstructures to achieve high performances.
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tuning phase composition of polymer nanocomposites toward high energy density and high discharge efficiency by Nonequilibrium Processing
ACS Applied Materials & Interfaces, 2017Co-Authors: Jianyong Jiang, Xin Zhang, Zhenkang Dan, Yuanhua Lin, Cewen Nan, Yang ShenAbstract:Polymer nanocomposite dielectrics with high energy density and low loss are major enablers for a number of applications in modern electronic and electrical industry. Conventional fabrication of nanocomposites by solution routes involves equilibrium Process, which is slow and results in structural imperfections, hence high leakage current and compromised reliability of the nanocomposites. We propose and demonstrate that a Nonequilibrium Process, which synergistically integrates electrospinning, hot-pressing and thermal quenching, is capable of yielding nanocomposites of very high quality. In the Nonequilibrium nanocomposites of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and BaTiO3 nanoparticles (BTO_nps), an ultrahigh Weibull modulus β of ∼30 is achieved, which is comparable to the quality of the bench-mark biaxially oriented polypropylene (BOPP) fabricated with melt-extrusion Process by much more sophisticated and expensive industrial apparatus. Favorable phase composition and small cry...
John D Chodera - One of the best experts on this subject based on the ideXlab platform.
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estimating equilibrium ensemble averages using multiple time slices from driven Nonequilibrium Processes theory and application to free energies moments and thermodynamic length in single molecule pulling experiments
Journal of Chemical Physics, 2011Co-Authors: David D L Minh, John D ChoderaAbstract:Recently discovered identities in statistical mechanics have enabled the calculation of equilibrium ensemble averages from realizations of driven Nonequilibrium Processes, including single-molecule pulling experiments and analogous computer simulations. Challenges in collecting large data sets motivate the pursuit of efficient statistical estimators that maximize use of available information. Along these lines, Hummer and Szabo developed an estimator that combines data from multiple time slices along a driven Nonequilibrium Process to compute the potential of mean force. Here, we generalize their approach, pooling information from multiple time slices to estimate arbitrary equilibrium expectations. Our expression may be combined with estimators of path-ensemble averages, including existing optimal estimators that use data collected by unidirectional and bidirectional protocols. We demonstrate the estimator by calculating free energies, moments of the polymer extension, the thermodynamic metric tensor, and...
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estimating equilibrium ensemble averages using multiple time slices from driven Nonequilibrium Processes theory and application to free energies moments and thermodynamic length in single molecule pulling experiments
Journal of Chemical Physics, 2011Co-Authors: David D L Minh, John D ChoderaAbstract:Recently discovered identities in statistical mechanics have enabled the calculation of equilibrium ensemble averages from realizations of driven Nonequilibrium Processes, including single-molecule pulling experiments and analogous computer simulations. Challenges in collecting large data sets motivate the pursuit of efficient statistical estimators that maximize use of available information. Along these lines, Hummer and Szabo developed an estimator that combines data from multiple time slices along a driven Nonequilibrium Process to compute the potential of mean force. Here, we generalize their approach, pooling information from multiple time slices to estimate arbitrary equilibrium expectations. Our expression may be combined with estimators of path-ensemble averages, including existing optimal estimators that use data collected by unidirectional and bidirectional protocols. We demonstrate the estimator by calculating free energies, moments of the polymer extension, the thermodynamic metric tensor, and the thermodynamic length in a model single-molecule pulling experiment. Compared to estimators that only use individual time slices, our multiple time-slice estimators yield substantially smoother estimates and achieve lower variance for higher-order moments.
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estimating equilibrium ensemble averages using multiple time slices from driven Nonequilibrium Processes theory and application to free energies moments and thermodynamic length in single molecule pulling experiments
arXiv: Statistical Mechanics, 2010Co-Authors: David D L Minh, John D ChoderaAbstract:Recently discovered identities in statistical mechanics have enabled the calculation of equilibrium ensemble averages from realizations of driven Nonequilibrium Processes, including single-molecule pulling experiments and analogous computer simulations. Challenges in collecting large data sets motivate the pursuit of efficient statistical estimators that maximize use of available information. Along these lines, Hummer and Szabo developed an estimator that combines data from multiple time slices along a driven Nonequilibrium Process to compute the potential of mean force. Here, we generalize their approach, pooling information from multiple time slices to estimate arbitrary equilibrium expectations. Our expression may be combined with estimators of path-ensemble averages, including existing optimal estimators that use data collected by unidirectional and bidirectional protocols. We demonstrate the estimator by calculating free energies, moments of the polymer extension, and the metric tensor for thermodynamic length in a model single-molecule pulling experiment. Compared to estimators that only use individual time slices, our multiple time-slice estimators yield substantially smoother estimates and achieve lower variance for higher-order moments.
Zhong Hui Shen - One of the best experts on this subject based on the ideXlab platform.
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high throughput phase field design of high energy density polymer nanocomposites
Advanced Materials, 2018Co-Authors: Yuanhua Lin, Cewen Nan, Zhong Hui Shen, Jianjun Wang, Longqing Chen, Yang ShenAbstract:Understanding the dielectric breakdown behavior of polymer nanocomposites is crucial to the design of high-energy-density dielectric materials with reliable performances. It is however challenging to predict the breakdown behavior due to the complicated factors involved in this highly Nonequilibrium Process. In this work, a comprehensive phase-field model is developed to investigate the breakdown behavior of polymer nanocomposites under electrostatic stimuli. It is found that the breakdown strength and path significantly depend on the microstructure of the nanocomposite. The predicted breakdown strengths for polymer nanocomposites with specific microstructures agree with existing experimental measurements. Using this phase-field model, a high throughput calculation is performed to seek the optimal microstructure. Based on the high-throughput calculation, a sandwich microstructure for PVDF-BaTiO3 nanocomposite is designed, where the upper and lower layers are filled with parallel nanosheets and the middle layer is filled with vertical nanofibers. It has an enhanced energy density of 2.44 times that of the pure PVDF polymer. The present work provides a computational approach for understanding the electrostatic breakdown, and it is expected to stimulate future experimental efforts on synthesizing polymer nanocomposites with novel microstructures to achieve high performances.
David D L Minh - One of the best experts on this subject based on the ideXlab platform.
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estimating equilibrium ensemble averages using multiple time slices from driven Nonequilibrium Processes theory and application to free energies moments and thermodynamic length in single molecule pulling experiments
Journal of Chemical Physics, 2011Co-Authors: David D L Minh, John D ChoderaAbstract:Recently discovered identities in statistical mechanics have enabled the calculation of equilibrium ensemble averages from realizations of driven Nonequilibrium Processes, including single-molecule pulling experiments and analogous computer simulations. Challenges in collecting large data sets motivate the pursuit of efficient statistical estimators that maximize use of available information. Along these lines, Hummer and Szabo developed an estimator that combines data from multiple time slices along a driven Nonequilibrium Process to compute the potential of mean force. Here, we generalize their approach, pooling information from multiple time slices to estimate arbitrary equilibrium expectations. Our expression may be combined with estimators of path-ensemble averages, including existing optimal estimators that use data collected by unidirectional and bidirectional protocols. We demonstrate the estimator by calculating free energies, moments of the polymer extension, the thermodynamic metric tensor, and...
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estimating equilibrium ensemble averages using multiple time slices from driven Nonequilibrium Processes theory and application to free energies moments and thermodynamic length in single molecule pulling experiments
Journal of Chemical Physics, 2011Co-Authors: David D L Minh, John D ChoderaAbstract:Recently discovered identities in statistical mechanics have enabled the calculation of equilibrium ensemble averages from realizations of driven Nonequilibrium Processes, including single-molecule pulling experiments and analogous computer simulations. Challenges in collecting large data sets motivate the pursuit of efficient statistical estimators that maximize use of available information. Along these lines, Hummer and Szabo developed an estimator that combines data from multiple time slices along a driven Nonequilibrium Process to compute the potential of mean force. Here, we generalize their approach, pooling information from multiple time slices to estimate arbitrary equilibrium expectations. Our expression may be combined with estimators of path-ensemble averages, including existing optimal estimators that use data collected by unidirectional and bidirectional protocols. We demonstrate the estimator by calculating free energies, moments of the polymer extension, the thermodynamic metric tensor, and the thermodynamic length in a model single-molecule pulling experiment. Compared to estimators that only use individual time slices, our multiple time-slice estimators yield substantially smoother estimates and achieve lower variance for higher-order moments.
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estimating equilibrium ensemble averages using multiple time slices from driven Nonequilibrium Processes theory and application to free energies moments and thermodynamic length in single molecule pulling experiments
arXiv: Statistical Mechanics, 2010Co-Authors: David D L Minh, John D ChoderaAbstract:Recently discovered identities in statistical mechanics have enabled the calculation of equilibrium ensemble averages from realizations of driven Nonequilibrium Processes, including single-molecule pulling experiments and analogous computer simulations. Challenges in collecting large data sets motivate the pursuit of efficient statistical estimators that maximize use of available information. Along these lines, Hummer and Szabo developed an estimator that combines data from multiple time slices along a driven Nonequilibrium Process to compute the potential of mean force. Here, we generalize their approach, pooling information from multiple time slices to estimate arbitrary equilibrium expectations. Our expression may be combined with estimators of path-ensemble averages, including existing optimal estimators that use data collected by unidirectional and bidirectional protocols. We demonstrate the estimator by calculating free energies, moments of the polymer extension, and the metric tensor for thermodynamic length in a model single-molecule pulling experiment. Compared to estimators that only use individual time slices, our multiple time-slice estimators yield substantially smoother estimates and achieve lower variance for higher-order moments.