介观电子谐振腔量子能谱与能量的量子涨落

针对介观电子谐振腔模型,在由电荷算符本征态构成的新Fock空间中,假设系统具有变换的对称性,通过求解Hamilton算符的本征值方程,给出系统的量子能谱关系.在电荷算符的Fock态下计算能量的量子涨落,分析和研究电子谐振腔的量子能谱性质.结果表明:类似于电荷的量子性,能谱明显地呈现出离散性,其大小决定于谐振腔的电参量、形状因子及栅极所加偏压等因素;而能量的量子涨落却仅与电荷量子、Planck常数以及系统自感有关.     

同位旋非对称核物质性质与扩展的BHF方法(Ⅶ)中子星物质中质子和中子的1S0态超流性

利用Brueckner Hartree Fock和BCS理论方法,计算了β稳定中子星物质中处于¹S₀ 态的质子和中子的对关联能隙,着重研究和讨论了三体核力的影响.结果表明三体核力对β稳定中子星物质中¹S₀态中子超流性的影响相对较小,但对¹S₀态质子超流性具有重要影响,而且其效应随核子数密度增大而迅速增强.三体核力的主要作用是强烈地抑制了高密度β稳定中子星物质中的1S0态质子超流性.     

核集体运动的耗散过程和内禀自由度趋向平衡过程的理论描述

对一个具有集体运动和内禀激发相互耦合的系统, 采用模型哈密顿量并同时考虑单体和两体相互作用, 讨论了集体运动和单粒子自由度的耦合. 得到的耦合方程组可描述集体运动的耗散动力学过程和内禀自由度趋向平衡的过程.     

1/N展开技术与sdg IBM的非SU(3)内禀态

本文利用1/N展开技术,讨论了sdg相互作用玻色子模型中由玻色子能量引起的SU(3)对称性破缺,给出了1/N近似下内禀态的解析表达式.本文还表明,相互作用玻色子体系的多体方法(Hartree-Bose方法、Tamm-Dancoff近似以及Cranked Hartree近似)均系1/N展开技术在特定情形下的近似.     

电子的谷自由度

电子在晶格周期性势场影响下的运动遵循布洛赫定理. 布洛赫电子除了具有电荷和自旋两个内禀自由度外, 还有其他内禀自由度. 能带色散曲线上的某些极值点作为谷自由度, 具有独特的电子结构和运动规律. 本文从布洛赫电子的谷自由度出发, 简单介绍传统半导体的谷电子性质研究现状, 并重点介绍新型二维材料体系, 如石墨烯、硅烯、硫族化合物等材料中谷相关的物理特性. 有效利用谷自由度的新奇输运特性, 将其作为信息的载体可以制作出新颖的纳米光电子器件, 并有望造就下一代纳电子器件的新领域, 即谷电子学(valleytronics).     

二次量子化中单体和两体算符的一种启发式推导

二次量子化是研究生和高年级本科生量子力学课程中的重要内容.如何从一次量子化中的多粒子哈密顿量及波函数出发,自然地导出二次量子化中由产生和湮没算符表示的单体和两体算符,是一个既关键且又使初学者较难理解的步骤.以全同费米子系统为例,本文给出该步骤的一种自然且具有启发性的推导方法.该方法仅依赖于:多粒子波函数的对称性假设,Fock空间中“真空填充”的概念,以及全反对称多粒子波函数与Fock态的等价性.     

光子两自由度超并行量子计算与超纠缠态操控

光子系统在量子信息处理和传输过程中有非常重要的应用. 譬如, 利用光子与原子(或人工原子)之间的相互作用, 可以完成信息的安全传输、存储和快速的并行计算处理等任务. 光子系统具有多个自由度, 如极化、空间模式、轨道角动量、时间-能量、频率等自由度. 光子系统的多个自由度可以同时应用于量子信息处理过程. 超并行量子计算利用光子系统多个自由度的光量子态同时进行量子并行计算, 使量子计算具有更强的并行性, 且需要的量子资源少, 更能抵抗光子数损耗等噪声的影响. 多个自由度同时存在纠缠的光子系统量子态称为超纠缠态, 它能够提高量子通信的容量与安全性, 辅助完成一些重要的量子通信任务. 在本综述中, 我们简要介绍了光子系统两自由度量子态在量子信息中的一些新应用, 包括超并行量子计算、超纠缠态分析、超纠缠浓缩和纯化三个部分.     

在不同初态下Dzyaloshinskii-Moriya相互作用及内禀退相干对海森伯系统的量子纠缠的影响

研究了存在内禀退相干时,对于不同的系统初态,具有DM相互作用和各向异性的三粒子XXZ海森伯模型的对纠缠动力学特性.得出了一些结论:系统的对纠缠度与各向异性参数?无关,但内禀退相干对系统的纠缠有明显的抑制作用;在内禀退相干存在时,若系统初态为纠缠态,选择合适的DM相互作用的参数,系统的对纠缠有一个非零的稳定值;系统初态为分离态时,系统的对纠缠会随时间震荡衰减,并且每次震荡会出现纠缠突然死亡现象,系统的对纠缠最终达到解纠缠状态.因此,选择合适的系统初态和DM相互作用参数可以有效地控制系统的对纠缠.     

采用MSDI严格角动量投影46Ti、48Cr形变HF谱

采用修正的表面δ相互作用(MSDI),以球形壳模型单粒子态作基矢,对fp壳层区偶偶核⁴⁶Ti、⁴⁸Cr进行形变Hartree–Fock(HF)计算,并用形变HF单粒子态构造Slater行列式波函数,即形变HF内禀态,然后对其实施严格角动量投影程序,得到比较合理的结果.     

具有非对角开边界的SU(2)不变Thirring模型的精确解

利用量子反散射方法研究了1+1维时空中具有非对角开边界条件下的SU(2)不变Thirring模型. 于辅助空间引入独立于谱参量的规范变换,找到了适当的Fock真空态. 通过Bethe Ansatz方法得到了系统相应转移矩阵的本征值和本征态,及其谱参数所满足的Bethe Ansatz方程,并讨论了体系的边界自由度. 关键词： SU(2)不变Thirring模型')" href="#">SU(2)不变Thirring模型 非对角开边界 量子反散射方法     

THE BEHAVIOR OF PARTONS OF LARGE TRANSVERSE MOMENTUM IN DEEP INELASTIC SCATTERING

The nucleonic states are represented by different configuration components in Fock space and the transverse momentum of partons is introduced as a degree of freedom into the structure function. In this way We calculated the contribution of the components of the valent quarks and the non-valent quarks of the charm state to the ratio of the longitudinal and the transverse cross sections of the virtual photons. A better agreement with the experimental data is obtained. The causes of deviation of the Callan-Gross relation from the experimental data is pointed out.     

Supersymmetry and positive temperature for simple systems

It has recently been argued by Girardello et al. that supersymmetry is automatically broken at positive temperature even when unbroken at T = 0, in the sense that the usual derivation of identities from unbroken supersymmetry does not automatically generalize to T > 0. Using as a guide simple examples with one bosonic and one fermionic degree of freedom, we study how supersymmetry reflects itself in the properties of excited states, in particular in the thermal properties at positive temperature. We derive a class of relations [see eq. 1.2)] which extend to all T the familiar consequences of unbroken supersymmetry for ground-state expectation values; these relations hold for unbroken and spontaneously broken supersymmetry. With Levine and Tomozawa we consider the algebra generated by the supercharges. In the case of two supercharges it can be reduced to the Clifford algebra of Pauli spin matrices, for which the eigenstates form irreducible doublets, except that a zero-energy eigenstate may be a singlet. The relations mentioned above are shown to hold for each doublet individually [see eq. (4,7)]. Some additional remarks are made on supersymmetry breaking at zero and positive temperatures.     

de Sitter QED

Attention is called to the fact that the well-known and straightforward generalization of electrodynamics to de Sitter space is incompatible with conformal invariance. In addition, there is difficulty in reconciling the space of one-photon states in de Sitter QED, for which the field carries no degree of freedom related to helicity, with that of flat space QED in which both signs of the helicity appear. The requirement of conformal invariance leads to the introduction of two vector potentials in de Sitter electrodynamics and resolves the helicity problem. A conformally invariant, indefinite metric quantization is carried out, and the nature of the flat space limit is clarified. Implications for a theory of composite massless particles are discussed, as well as applications to supersymmetry and supergravity.     

Supersymmetry versus integrability in two-dimensional classical mechanics

Supersymmetric extensions of Hamilton-Jacobi separable Liouville mechanical systems with two degrees of freedom are defined. It is shown that supersymmetry can be implemented in this type of systems in two independent ways. The structure of the constants of motion is unveiled and the entanglement between integrability and supersymmetry is explored.     

Hidden supersymmetry in quantum bosonic systems

We show that some simple well-studied quantum mechanical systems without fermion (spin) degrees of freedom display, surprisingly, a hidden supersymmetry. The list includes the bound state Aharonov-Bohm, the Dirac delta and the Pöschl-Teller potential problems, in which the unbroken and broken N = 2 supersymmetry of linear and nonlinear (polynomial) forms is revealed.     

Non‐linear Realizations and Higher Curvature Supergravity

We focus on non‐linear realizations of local supersymmetry as obtained by using constrained superfields in supergravity. New constraints, beyond those of rigid supersymmetry, are obtained whenever curvature multiplets are affected as well as higher derivative interactions are introduced. In particular, a new constraint, which removes a very massive gravitino is introduced, and in the rigid limit it merely reduces to an explicit supersymmetry breaking. Higher curvature supergravities free of ghosts and instabilities are also obtained in this way. Finally, we consider direct coupling of the goldstino multiplet to the super Gauss–Bonnet multiplet and discuss the emergence of a new scalar degree of freedom.     

Supersymmetries and BPS configurations on anti-de Sitter space

We study supersymmetry breaking due to the presence of branes on anti-de Sitter space and obtain conditions for brane orientations not to break too many supersymmetries. Using the conditions, we construct a brane configuration corresponding to a baryon in large N gauge theory, and it is shown that the baryon is a marginal bound state of quarks, as is expected from supersymmetry.     

External inversion,internal inversion,and reflection invariance

Having in mind that physical systems have different levels of structure we develop the concept of external, internal and total improper Lorentz transformation (space inversion and time reversal). A particle obtained from the ordinary one by the application of internal space inversion or time reversal is generally a different particle. From this point of view the intrinsic parity of a nuclear particle (elementary particle) is in fact the external intrinsic parity, if we take into account the internal structure of a particle. We show that non-conservation of the external parity does not necessarily imply noninvariance of nature under space inversion. The conventional theory of beta-decay can be corrected by including the internal degrees of freedom to become invariant under total space inversion, though not under the external one.     

A Nonperturbative Regularization of the Supersymmetric Schwinger Model

It is shown that noncommutative geometry is a nonperturbative regulator which can manifestly preserve a space supersymmetry and a supergauge symmetry while keeping only finite number of degrees of freedom in the theory. The simplest N= 1 case of the U(1) supergauge theory on the sphere is worked out in detail. Received: 15 March 1999 / Accepted: 8 April 1999     

Supersymmetry and Integrability in Planar Mechanical Systems

We present an N=2-supersymmetric mechanical system whose bosonic sector, with two degrees of freedom, exhibits the most general possible supersymmetric fourth order potential, including the interesting case of SU(2) Yang–Mills theory. The Painlevé test is adopted to discuss integrability and we focus on the rôle of supersymmetry and parity invariance in two space dimensions for the attainment of integrable or non-integrable models, with some remarks on the chaotic behavior. Our result shows that, for the model studied here, the relationships among the parameters, as imposed by supersymmetry, restrict the parameter space in such a way that the reduction on its non-integrable sector is much more severe than on its integrable sector (especially on the non-separable subset of the latter), thus suggesting that supersymmetry may favor (mainly non-separable) integrability.