The Experts below are selected from a list of 17163 Experts worldwide ranked by ideXlab platform
Joseph E Subotnik - One of the best experts on this subject based on the ideXlab platform.
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on the proper derivation of the floquet based quantum classical liouville equation and surface hopping describing a molecule or material subject to an external field
Journal of Chemical Physics, 2020Co-Authors: Hsingta Chen, Zeyu Zhou, Joseph E SubotnikAbstract:We investigate different approaches to derive the proper Floquet-based quantum-classical Liouville equation (F-QCLE) for laser-driven electron-nuclear dynamics. The first approach projects the operator form of the standard QCLE onto the diabatic Floquet basis and then transforms to the adiabatic representation. The second approach directly projects the QCLE onto the Floquet adiabatic basis. Both approaches yield a form that is similar to the usual QCLE with two modifications: (1) The electronic degrees of freedom are expanded to infinite dimension and (2) the nuclear motion follows Floquet quasi-energy surfaces. However, the second approach includes an additional Cross Derivative force due to the dual dependence on time and nuclear motion of the Floquet adiabatic states. Our analysis and numerical tests indicate that this Cross Derivative force is a fictitious artifact, suggesting that one cannot safely exchange the order of Floquet state projection with adiabatic transformation. Our results are in accord with similar findings by Izmaylov et al., [J. Chem. Phys. 140, 084104 (2014)] who found that transforming to the adiabatic representation must always be the last operation applied, although now we have extended this result to a time-dependent Hamiltonian. This paper and the proper derivation of the F-QCLE should lay the basis for further improvements of Floquet surface hopping.
Hsingta Chen - One of the best experts on this subject based on the ideXlab platform.
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on the proper derivation of the floquet based quantum classical liouville equation and surface hopping describing a molecule or material subject to an external field
Journal of Chemical Physics, 2020Co-Authors: Hsingta Chen, Zeyu Zhou, Joseph E SubotnikAbstract:We investigate different approaches to derive the proper Floquet-based quantum-classical Liouville equation (F-QCLE) for laser-driven electron-nuclear dynamics. The first approach projects the operator form of the standard QCLE onto the diabatic Floquet basis and then transforms to the adiabatic representation. The second approach directly projects the QCLE onto the Floquet adiabatic basis. Both approaches yield a form that is similar to the usual QCLE with two modifications: (1) The electronic degrees of freedom are expanded to infinite dimension and (2) the nuclear motion follows Floquet quasi-energy surfaces. However, the second approach includes an additional Cross Derivative force due to the dual dependence on time and nuclear motion of the Floquet adiabatic states. Our analysis and numerical tests indicate that this Cross Derivative force is a fictitious artifact, suggesting that one cannot safely exchange the order of Floquet state projection with adiabatic transformation. Our results are in accord with similar findings by Izmaylov et al., [J. Chem. Phys. 140, 084104 (2014)] who found that transforming to the adiabatic representation must always be the last operation applied, although now we have extended this result to a time-dependent Hamiltonian. This paper and the proper derivation of the F-QCLE should lay the basis for further improvements of Floquet surface hopping.
Zeyu Zhou - One of the best experts on this subject based on the ideXlab platform.
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on the proper derivation of the floquet based quantum classical liouville equation and surface hopping describing a molecule or material subject to an external field
Journal of Chemical Physics, 2020Co-Authors: Hsingta Chen, Zeyu Zhou, Joseph E SubotnikAbstract:We investigate different approaches to derive the proper Floquet-based quantum-classical Liouville equation (F-QCLE) for laser-driven electron-nuclear dynamics. The first approach projects the operator form of the standard QCLE onto the diabatic Floquet basis and then transforms to the adiabatic representation. The second approach directly projects the QCLE onto the Floquet adiabatic basis. Both approaches yield a form that is similar to the usual QCLE with two modifications: (1) The electronic degrees of freedom are expanded to infinite dimension and (2) the nuclear motion follows Floquet quasi-energy surfaces. However, the second approach includes an additional Cross Derivative force due to the dual dependence on time and nuclear motion of the Floquet adiabatic states. Our analysis and numerical tests indicate that this Cross Derivative force is a fictitious artifact, suggesting that one cannot safely exchange the order of Floquet state projection with adiabatic transformation. Our results are in accord with similar findings by Izmaylov et al., [J. Chem. Phys. 140, 084104 (2014)] who found that transforming to the adiabatic representation must always be the last operation applied, although now we have extended this result to a time-dependent Hamiltonian. This paper and the proper derivation of the F-QCLE should lay the basis for further improvements of Floquet surface hopping.
Stephane Couture - One of the best experts on this subject based on the ideXlab platform.
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risk management activities of a non industrial private forest owner with a bivariate utility function
Review of Agricultural Food and Environmental Studies, 2018Co-Authors: Marielle Brunette, Stephane CoutureAbstract:We analyze the insurance and self-insurance choices of a private forest owner whose utility is bivariate (consumption and forest amenity value). We show that under fair premium, full insurance is optimal only if the Cross Derivative of the utility function is equal to zero, whereas under unfair premium, optimal partial insurance is validated only if the Cross Derivative is positive. We also show that insurance and self-insurance may be substitutes, and if preferences are separable and the cost of insurance is not so high, then insurance and self-insurance are always considered as substitutes. However, we find in an illustration with a non-separable bivariate utility function, characterized by weights given to consumption and amenities, that insurance and self-insurance are complement. We obtain that the weight given to amenities substantially affects optimal risk management activities for unfair insurance. These results highlight the importance to represent the forest owner’s behavior through a bivariate utility function.
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Risk management activities of a non-industrial private forest owner with a bivariate utility function
2014Co-Authors: Marielle Brunette, Stephane CoutureAbstract:In this paper, we propose to analyse the choice of risk management activity made by a nonindustrial private forest owner who derives utility from consumption and from the sentimental value of the forest that bears a risk of disaster. We consider a bivariate utility function depending on consumption and sentimental value of forest. In this context, we analyse insurance and/or self-insurance decisions. We show that, under fair premium, full insurance is optimal only if the Cross Derivative of the utility function equals zero. Under-insurance and over-insurance may also be optimal depending on the sign of this Cross Derivative. We also show that, under a positive loading factor, optimal partial insurance is validated only if the Cross Derivative is positive; otherwise full insurance may be optimal even with a loading insurance. We also observe that risk aversion increases the level of insurance demand and self-insurance activity, extending this standard result obtained with an univariate utility function to a bivariate utility function. Moreover, when the forest owner can simultaneously insure and invest in self-insurance activity, full insurance is never optimal if the Cross Derivative is positive. Finally, we prove that insurance and self-insurance may be substitutes, and if preferences are separable and exhibit decreasing absolute risk aversion, then insurance and self-insurance are always considered as substitutes.
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risk management activities of a non industrial priv ate forest owner with a bivariate utility function
Journées internationales du Risque, 2014Co-Authors: Marielle Brunette, Stephane CoutureAbstract:In this paper, we propose to analyse the choice of risk management activity made by a non-industrial private forest owner who derives utility from consu mption and from the sentimental value of the forest that bears a risk of disaster. We consider a bivari ate utility function depending on consumption and sentimental value of forest. In this context, we an alyse insurance and/or self-insurance decisions. We show that, under fair premium, full insurance is op timal only if the Cross Derivative of the utility function equals zero. Under-insurance and over-insu rance may also be optimal depending on the sign of this Cross Derivative. We also show that, under a positive loading factor, optimal partial insuranc e is validated only if the Cross Derivative is positive; otherwise full insurance may be optimal even with a loading insurance. We also observe that risk aversi on increases the level of insurance demand and self insurance activity, extending this standard result obtained with an univariate utility function to a bivariate utility function. Moreover, when the forest owner can simultaneously insure and invest in self-insurance activity, full insurance is never optimal if the Cross Derivative is positive. Finally, we prove that insurance and s elfinsurance may be substitutes, and if preferences ar e separable and exhibit decreasing absolute risk aversion, then insurance and self-insurance are alw ays considered as substitutes.
Z Y Xie - One of the best experts on this subject based on the ideXlab platform.
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Cross Derivative of the gibbs free energy a universal and efficient method for phase transitions in classical spin models
Physical Review B, 2020Co-Authors: Yan Chen, Z Y XieAbstract:With an auxiliary weak external magnetic field, we reexamine the fundamental thermodynamic function, Gibbs free energy $G(T,h)$, to study phase transitions in classical spin lattice models. A Cross Derivative, i.e., the second-order partial Derivative of $G(T,h)$ with respect to both temperature and field, is calculated to precisely locate the critical temperature, which also reveals the nature of a transition. The strategy is efficient and universal, as exemplified by the five-state clock model, two-dimensional (2D) and 3D Ising models, and the $XY$ model, no matter if a transition is trivial or exotic with complex excitations. More importantly, other conjugate pairs could also be integrated into a similar Cross Derivative if necessary, which would greatly enrich our vision and means to investigate phase transitions both theoretically and experimentally.