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Synthesizing and controlling helical indirect exchange interactions out of equilibrium

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Physical Review B 2018年第18期98卷 184426-184426页

作者： Tingting Liu Jie Ren Peiqing Tong Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing 210023 P. R. China Center for Phononics and Thermal Energy Science China-EU Joint Center for Nanophononics Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology School of Physics Science and Engineering Tongji University Shanghai 200092 P. R. China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 P. R. China

We study the nonequilibrium effects of spin and/or electric currents on the helical indirect exchange interactions of local spins that embedded in general open electronic systems. Especially, besides the synthesized anisotropic Heisenberg interactions, we find that the synthetic helical indirect exchange interactions possess two parts: antisymmetric (Dzyaloshinskii-Moriya interaction) and symmetric (Kaplan-Shekhtman-Entin-Wohlman-Aharony interaction), which are all formulated in terms of Keldysh nonequilibrium Green's functions. The presence of either spin-orbit coupling or spin polarized currents alone is able to synthesize and control the antisymmetric Dzyaloshinskii-Moriya exchange interactions, as the same direction as spin splitting. However, the appearance of symmetric Kaplan-Shekhtman-Entin-Wohlman-Aharony interactions requires both, i.e., the spin-orbit coupling and spin polarized currents with different splitting directions. Our results show the detailed scheme of controlling the sign, magnitude, and direction of indirect Dzyaloshinskii-Moriya vectors and Kaplan-Shekhtman-Entin-Wohlman-Aharony interactions at nonequilibrium in open quantum devices.

关键词： Dzyaloshinskii-Moriya interaction Exchange interaction Open quantum systems RKKY interaction Rashba coupling

Comparison and Modification: TVD Schemes for Scalar Transport on An Unstructured Grid

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China Ocean Engineering 2016年第4期30卷 615-626页

作者：张卓宋志尧郭飞张东温永宁胡迪 Key Lab of Virtual Geographic Environment under Ministry of Education Nanjing Normal University Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing Normal University Jiangsu Key Lab for Numerical Simulation of Large-Scale Complex System Nanjing Normal University

In most TVD schemes, the r-factors were proposed according to the cell-centered（CC） finite volume method（FVM） framework for the numerical approximation to the convective term. However, it is questionable whether those r-factors would be appropriate and effective for the vertex-centered（VC） FVM. In the paper, we collected five kinds of r-factor formulae and found out that only three of those, respectively by Bruner（1996）, Darwish and Moukalled（2003） and Cassuli and Zanolli（2005） can be formally extended to a context of the VC FVM. numerical tests indicate that the TVD schemes and r-factors, after being extended and introduced to a context of the VC FVM, maintained their similar characteristics as in a context of the CC FVM. However, when the gradient-based r-factors and the SUPERBEE scheme were applied simultaneously, non-physical oscillations near the sharp step would appear. In the transient case, the oscillations were weaker in a context of the VC FVM than those in a context of the CC FVM, while the effect was reversed in the steady case. To eliminate disadvantages in the gradient-based r-factor formula, a new modification method by limiting values on the virtual node, namely Фu in the paper, was validated by the tests to effectively dissipate spurious oscillations.

关键词： TVD scheme unstructured grid vertex-centered FVM flux limiter, r-factor

The global existence and large time behavior of smooth compressible fluid in an infinitely expanding ball, I: 3D Euler equations

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arXiv 2017年

作者： Xu, Gang Yin, Huicheng Faculty of Science Jiangsu University Zhenjiang Jiangsu212013 China School of Mathematical Sciences Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

We concern with the global existence and large time behavior of compressible fluids (including the inviscid gases, viscid gases, and Boltzmann gases) in an infinitely expanding ball. Such a problem is one of the interesting models in studying the theory of global smooth solutions to multidimensional compressible gases with time dependent boundaries and vacuum states at infinite time. Due to the conservation of mass, the fluid in the expanding ball becomes rarefied and eventually tends to a vacuum state meanwhile there are no appearances of vacuum domains in any part of the expansive ball, which is easily observed in finite time. In this paper, as the first part of our three papers, we will confirm this physical phenomenon for the compressible inviscid fluids by obtaining the exact lower and upper bound on the density function. Copyright © 2017, The Authors. All rights reserved.

关键词： Euler equations

simulation of Centennial-scale Drought Events over Eastern China during the Past 1500 Years

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Journal of Meteorological Research 2017年第1期31卷 17-27页

作者： Weiyi SUN Jian LIU Zhiyuan WANG key laboratory for virtual geographic environment(nanjing normal university) ministry of educationstate key laboratory cultivation base of geographical environment evolution(jiangsu province)School of Geography ScienceNanjing Normal UniversityNanjing 210023 Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems School of Mathematical ScienceNanjing Normal UniversityNanjing 210023 Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing 210023

The characteristics and causes of centennial-scale drought events over eastern China during the past 1500 years were explored based on simulations of the Community Earth system Model （CESM）. The results show that centenni- al-scale drought events over eastern China occurred during the periods of 622-735 （Drought period 1, D1） and 1420-1516 （Drought period 2, D2） over the past 1500 years, which is comparable with climate proxy data. In D1, the drought center occurred in northern China and the Yangtze River valley; however, in southern China, precipitation was much more than usual. In D2, decreased precipitation was found across almost the whole region of eastern China. The direct cause of these two drought events was the weakened East Asian summer monsoon, and the specif- ic process was closely linked to the air-sea interaction of the Indo-Pacific Ocean. In DI, regions of maximum cool- ing were observed over the western Pacific, which may have led to anomalous subsidence, weakening the Walker cir- culation, and reducing the northward transport of water vapor. Additionally, upward motion occurred over southern China, strengthening convection and increasing precipitation. In D2, owing to the decrease in the SST, subsidence dominated the North Indian Ocean, blocking the low-level cross-equatorial flow, enhancing the tropical westerly an- omalies, and reducing the northward transport of moisture. Additionally, descending motion appeared in eastern China, subsequently decreasing the precipitation over the whole region of eastern China. The anomalous cooling of the Indo-Pacific Ocean SST may have been caused by the persistently low solar irradiation in D1; whereas, in D2, this characteristic may have been influenced not only by persistently low solar irradiation, but frequent volcanic erup- tions too.

关键词： CESM centennial-scale drought eastern China East Asian summer monsoon

Quasi-two-body decays Bc → D(s)[ρ(770), ρ(1450), ρ(1700) →]ππ in the perturbative QCD factorization approach

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arXiv 2017年

作者： Ma, Ai-Jun Li, Ya Xiao, Zhen-Jun Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing Jiangsu210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing Jiangsu210023 China

In this paper, we studied the quasi-two-body Bc → D(s)[ρ(770), ρ(1450), ρ(1700) →]ππ decays by employing the perturbative QCD (PQCD) factorization approach. The two-pion distribution amplitudes φππ are applied to include the final-state interactions between the pion pair, while the time-like form factors Fπ(w2) associated with the P-wave resonant states ρ(770), ρ(1450) and ρ(1700) are extracted from the experimental data of the e+e-annihilation. We found that: (a) the PQCD predictions for the branching ratios of the quasi-two-body Bc → D(s)[ρ(770), ρ(1450), ρ(1700) →]ππ decays are in the order of 10-9 to 10-5 and the direct CP violations around (10 - 40)% in magnitude;(b) the two sets of the large hierarchy R1a,1b,1c and R2a,2b,2c for the ratios of the branching ratios of the considered decays are defined and can be understood in the PQCD factorization approach, while the self-consistency between the quasi-two-body and two-body framework for Bc → D(s)[ρ(770) →]ππ and Bc → D(s)ρ(770) decays are confirmed by our numerical results;(c) taking currently known B(ρ(1450) → ππ) and B(ρ(1700) → ππ) as input, we extracted the theoretical predictions for B(Bc → Dρ(1450)) and B(Bc → Dρ(1700)) from the PQCD predictions for the decay rates of the quasi-two-body decays Bc → D[ρ(1450), ρ(1700) →]ππ. All the PQCD predictions will be tested in the future experiments. Copyright © 2017, The Authors. All rights reserved.

关键词： Hadrons

Investigating the excited ω 0 c states through c K and c K decay channels

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arXiv 2017年

作者： Huang, Hongxia Ping, Jialun Wang, Fan Dept. of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China Department of Physics Nanjing University Nanjing210093 China

Inspired by the five newly observed ω 0 c states by the LHCb detector, we study the ω 0 c states as the Swave molecular pentaquarks with I = 0, JP = 1 2 , 3 2 , and 5 2 by solving the RGM equation in the framework of chiral quark model. Both the energies and the decay widths are obtained in this work. Our results suggest that c(3119)0 can be explained as an Swave resonance state of D with JP = 1 2 , and the decay channels are the Swave cK and cK . Other reported ω 0 c states cannot be obtained in our present calculation. Another ω 0 c state with much higher mass 3533 MeV with JP = 5 2 is also obtained. In addition, the calculation is extended to the 0 b states, similar results as that of ω 0 c are obtained. Copyright © 2017, The Authors. All rights reserved.

关键词： Hadrons

Structure of pentaquarks Pc+ in the chiral quark model

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Physical Review D 2017年第1期95卷 014010-014010页

作者： Gang Yang Jialun Ping Fan Wang Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 People’s Republic of China Department of Physics Nanjing University Nanjing 210093 People’s Republic of China

The recent experimental results of the LHCb Collaboration suggested the existence of pentaquark states with a charmonium. To understand the structure of the states, a dynamical calculation of 5-quark systems with quantum numbers IJP=12(12)±, 12(32)± and 12(52)± is performed in the framework of the chiral quark model with the help of the Gaussian expansion method. The results show that there are several negative parity resonance states while all of the positive parity states are the scattering states. The Pc(4380) state is suggested to be the pentaquark state of Σc*D¯. Although the energy of ΣcD¯* is very close to the mass of Pc(4450), the inconsistent parity prevents the assignment. The calculated distances between quarks confirm the molecular nature of the states.

关键词： Hadron-hadron interactions Quark model Exotic baryons

The global existence and large time behavior of smooth compressible fluid in an infinitely expanding ball, III: The 3-D Boltzmann equation

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arXiv 2017年

作者： Yin, Huicheng Zhao, Wenbin School of Mathematical Sciences Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China Department of Mathematics and IMS Nanjing University Nanjing210093 China

This paper is a continuation of the works in [34] and [36], where the authors have established the global existence of smooth compressible flows in infinitely expanding balls for inviscid gases and viscid gases, respectively. In this paper, we are concerned with the global existence and large time behavior of compressible Boltzmann gases in an infinitely expanding ball. Such a problem is one of the interesting models in studying the theory of global smooth solutions to multidimensional compressible gases with time dependent boundaries and vacuum states at infinite time. Due to the conservation of mass, the fluid in the expanding ball becomes rarefied and eventually tends to a vacuum state meanwhile there are no appearances of vacuum domains in any part of the expansive ball, which is easily observed in finite time. In the present paper, we will confirm this physical phenomenon for the Boltzmann equation by obtaining the exact lower and upper bound on the macroscopic density function. Copyright © 2017, The Authors. All rights reserved.

关键词： Boltzmann equation

On the global existence and stability of 3-D viscous cylindrical circulatory flows

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arXiv 2017年

作者： Yin, Huicheng Zhang, Lin School of Mathematical Sciences Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China Department of Mathematics and IMS Nanjing University Nanjing210093 China

In this paper, we are concerned with the global existence and stability of a 3-D perturbed viscous circulatory flow around an infinite long cylinder. This flow is described by 3-D compressible Navier-Stokes equations. By introducing some suitably weighted energy spaces and establishing a priori estimates, we show that the 3-D cylindrical symmetric circulatory flow is globally stable in time when the corresponding initial states are perturbed suitably small. Copyright © 2017, The Authors. All rights reserved.

关键词： Viscous flow