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Direct CP violation in hadronic B decays

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Science China(physics,Mechanics & Astronomy) 2006年第3期49卷 357-366页

作者： HONG Bihai1.2 & Lü Caidian3 1. department of {1., Lishui university, Lishui 323000,China 2. department of {1., Shanghai Jiaotong university, Shanghai 200030, China 3. Institute of High Energy {1., Beijing 1.0049,China department of {1. Lishui University Lishui 323000 China department of {1. Shanghai Jiaotong University Shanghai 200030 China Institute of High Energy physics Beijing 100049 China

There are different approaches for the hadronic B decay calculations, recently. In this paper, we upgrade three of them, namely factorization, QCD factorization and the perturbative QCD approach based on kT factorization, using new parameters and full wave functions. Although they get similar results for many of the branching ratios, the direct CP asymmetries predicted by them are different, which can be tested by recent experimental measurements of B factories.

关键词： CP violation hadronic B decay factorization.

Negative differential resistance in molecular devices: the role of molecule-electrode coupling

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Science China(physics,Mechanics & Astronomy) 2011年第8期Mechanics & Astronomy) .卷 1455-1460页

作者： ZHAI YaXin1. JI GuoMin1. FANG ChangFeng1. CUI Bin1. ZHAO Peng2 & LIU DeSheng1.3, 1.School of physics, State Key Laboratory of Crystal Materials, Shandong {1., Jinan 2501.0, China 2 School of Science, {1. of Jinan, Jinan 250022, China 3 department of physics and Information Engineering, jining university, qufu 2731.0, China 1. School of physics State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China2. School of Science University of Jinan Jinan 250022 China3. Department of Physics and Information Engineering Jining University Qufu 273100 China

By applying nonequilibrium Green's function formalism combined with the first-principles density functional theory, we investigate the electronic transport in two molecular junctions constituted by a substituted oligo (phenylene ehtynylene) sand-wiched between two Au electrodes. Our calculations show that the weak molecule-electrode coupling is responsible for the observation of the negative differential resistance (NDR) effect in experiments. When the coupling is weak, the projected density of states (PDOS) of the molecule and the electrodes undergoes a mismatch-match-mismatch procedure, which increases and then decreases the transmission peak intensities, leading to a NDR effect. We also find that the localization/delocalization of the molecular orbitals and the change of charge state of the molecule have no direct relation with the NDR effect, because they change little as the voltage increases.

关键词： negative differential resistance substituted oligo (phenylene ehtynylene) molecular junction density functional theory nonequilibrium Green’s function formalism

Effect of an impurity on 3-electron quantum dots in magnetic fields

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Science China(physics,Mechanics & Astronomy) 2004年第5期47卷 521-530页

作者： LIU Yimin1.2, HUANG Gangming1.& BAO Chengguang1.1. department of {1., Zhongshan university, Guangzhou 51.275, China 2. department of {1., Shaoguan university, Shaoguan 51.005, China 1. department of {1. Zhongshan University 510275 Guangzhou China 2. department of {1. Shaoguan University 512005 Shaoguan China

The ground-state property of a 2-dimensional 3-electron quantum dot (QD) subjected to an external magnetic fieldB and affected by an impurity is studied. The impurity is located at thez-axis by a distanced from the plane of the dot. The evolution of the angular momentumL o and the spinS o of the ground state in accordance withB andd has been calculated, and the results are summarized and plotted in a (L o,S o) diagram. The spatial distribution of the electrons (the size and the geometric features) and the optical absorption have also been investigated. The (L o S o) diagram indicates thatL o andS o may jump whend and/orB vary. It was found that, due to the constraints arising from symmetry, each symmetric geometry is accessible only to a specific group of states having specificL o andS o.

关键词： quantum dot, ground state, charged impurity, magnetic field.

Study on the two and three-parameter working stability regions of 3Y-TZP suspension

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Science China(Technological Sciences) 2006年第5期49卷 547-568页

作者： CHEN Youqiang1. 2, ZHANG Xinni3, CHEN Sha’ou3 & QI Ping3 1. department of Chemistry, Qingdao {1., Qingdao 266071. China 2. department of Chemistry, Tsinghua {1., Beijing 1.0084, China 3. department of physics, Qingdao {1., Qingdao 266071. China 1. department of Chemistry Qingdao University Qingdao 266071 China 2. department of Chemistry Tsinghua University Beijing 100084 China 3. department of {1. Qingdao University Qingdao 266071 China

We determined the variation tendency of viscosity (η) at various solids load- ing (α) for 3Y-TZP suspension as a function of dispersant concentration (Cw) using vis- cosity measurement, measured the diameter of particles as a function of Cw in very dilute suspension using light scattering method, and obtained the surface features of the sedi- ment of suspension with different Cw using SEM. We also discussed the influence of the microstructure of adsorbed polymer layers on particles and their interactions in the dis- persing medium on the stability of suspension. Then two different stable states and two different unstable states for 3Y-TZP suspension were given. Accordingly, the (Cw, η), (Cw, α), and (α, η) two-parameter, and (Cw, α, η) three-parameter stability maps were con- structed. Based on the DLVO theory calculations, the dispersant concentration, particle distance (r), and interparticle potential energy (VT) maps with various solids loading for 3Y-TZP aqueous suspension were also constructed. In (Cw, r) two-parameter coordinate system, the stable motion region map for particles was established. The Cw, α, and VT,max (the highest potential energy) surface of the potential barrier map was obtained through calculation and simulation on the basis of the surfaces of Cw, r, VT maps introduced above. The (Cw, α) two-parameter stability map was then obtained from the Cw, α, VT,max map. The results showed that this theoretical map can qualitatively prove the experimentally obtained results—the existence of different dispersed states of particles in suspension system and the variation tendency of suspension stability with changing each parame- ter—were reasonable.

关键词： 3Y-TZP, suspension, stability, DLVO theory, interparticle potential energy.

Superconductivity of small metal grains

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Science China(physics,Mechanics & Astronomy) 2005年第4期48卷 431-441页

作者： ZHENG Renrong1.CHEN Zhiqian2 & ZHU Shunquan1.3 1. department of {1., Shanghai Normal university, Shanghai 200234, China 2. department of {1., Southwest Normal university, Chongqing 40071., China 3. department of Computer and Electric Technology, Shanghai Business School, Shanghai 201.00, China 1. department of {1. Shanghai Normal University 200234 Shanghai China 2. department of {1. Southwest Normal University 400715 Chongqing China 3. department of Computer and Electric Technology Shanghai Business School 201400 Shanghai China

The formulas of the energy gap and superconducting critical temperature appropriate for systems with both odd and even number of electrons are derived; the bases of the derivations are BCS theory and energy level statistics. Numerical results qualitatively agree with the experimental phenomena. i.e., the superconductivity of small metallic grains will first enhance then decrease to zero when the grain are getting smaller and smaller. The calculations indicate that the above phenomena happen in the metallic grains belonging to Gaussian Orthogonal Ensemble (GOE) and Gaussian Unitary ensemble (GUE) with zero spin; The superconductivity of small metallic grains in Gaussian Symplectic Ensemble (GSE) will monotonically decrease to zero with the decreasing of the grain size. The analyses suggest that the superconductivity enhancements come from pairing and the balance of the strengths between spin-orbital coupling and external magnetic field. In order to take the latter into account, it is necessary to include the level statistics given by Random Matrix Theory (RMT) in describing small metallic grains.

关键词： size effect, superconductivity enhancements, small metallic grains.

Density-functional formula for strongly correlated systems

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Progress in Natural Science:Materials International 2005年第5期15卷 395-401页

作者： WANG Huaiyu1.*, HAN Rushan2 and CHEN Nanxian1.1. department of {1., Tsinghua university, Beijing 1.0084, China 2. department of {1., Peking university, Beijing 1.0871. China) department of {1. Tsinghua University Beijing 100084 China department of {1. Peking University Beijing 100871 China

Density functional method is applied for strongly correlated systems. Based on the assumption that the systems are composed of electrons in singly-occupied orbitals and those in doubly-occupied orbitals, a set of self-consistent equations are obtained by standard variation procedure. The equations consist of two parts. One part is to solve the wave functions of the electrons in singly-occupied orbitals and the other is to solve the wave functions of the electrons in doubly-occupied orbitals. The physical meanings of the terms appearing in the equations are discussed.

关键词： density-functional theory strongly correlated systems doubly-occupied orbital two-particle wave function self-consistent equations.

Stochastic resonance in surface catalytic oxidation of carbon monoxide induced by colored noise

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Science China Chemistry 2004年第2期47卷 106-112页

作者： GONG Yubing1.2, HOU Zhonghuai1.& XIN Houwen1.1. department of Chemical {1., university of Science and Technology of China, Hefei 230026, China 2. department of {1., Yantai Teachers university, Yantai 264025, China 1. department of Chemical {1. University of Science and Technology of China 230026 Hefei China 2. department of {1. Yantai Teachers University 264025 Yantai China

The dynamical behavior of surface catalytic oxidation reaction of Pt(1.0)/CO+O2 modulated by colored noise, under the condition of specific temperature, has been investigated when the partial pressure of CO gas is near the supercritical Hopf bifurcation point. By computer simulation the oscillation and stochastic resonance induced by colored noise are observed. The influences of the intensity and correlation time of colored noise on stochastic resonance are discussed. The range of sensitivity of the system to the environmental fluctuation is analyzed.

关键词： colored noise, stochastic resonance, surface catalytic reaction of Pt(1.0)/CO+O2, supercritical Hopf bifurcation, signal-to-noise ratio (SNR).

Conditions on converting coherence into entanglement

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Chinese physics B 2017年第8期26卷 46-49页

作者：杨连武夏云杰 Shandong Provincial Key Laboratory of Laser Polarization and Information Technology Department of PhysicsQufu Normal University department of {1. and Information Engineering Jining University

The present studies show that any nonzero amount of coherence of a system can be converted into entanglement between the system and an incoherent ancillary system via incoherent operations. According to this conclusion, we study the process of converting coherence into entanglement via a unitary operation where the initial ancillary system is of different quantum state. We find that some other conditions should be satisfied in converting coherence into entanglement. We also study the conditions of coherence consumption of converting coherence into entanglement.

关键词： coherence entanglement conditions

Internal noise stochastic resonance in CO oxidation on nm-sized palladium particles

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Science China Chemistry 2005年第5期48卷 395-401页

Based on a stochastic mesoscopic model, the influence of internal noise on the oscillatory kinetics of the catalytic oxidation of CO on nm-sized palladium particles is studied, using the chemical Langevin equations, Poisson approximation algorithm, and exact stochastic simulation algorithm. The reaction rate oscillations are of stochastic nature due to considerable internal noise in such mesoscopic systems. It is found that the performance of the stochastic oscillations undergoes a maximum with the variation of internal noise level for a given CO partial pressure, which demonstrates the occurrence of internal noise stochastic resonance. This phe-nomenon implies that optimal internal noise would favor the reaction rate oscillation of CO oxi-dation on nm particles. Such a phenomenon is robust to the change of external parameters, such as CO pressures.

关键词： nanometer-sized palladium particles, surface catalytic CO oxidation, internal noise, stochastic resonance, chemical Langevin equation.