Graded irreducible representations of Leavitt path algebras: A new type and complete classification

We present a new class of graded irreducible representations of a Leavitt path algebra. This class is new in the sense that its representation space is not isomorphic to any of the existing simple Chen modules. The corresponding graded simple modules complete the list of Chen modules which are graded, creating an exhaustive class: the annihilator of any graded simple module is equal to the annihilator of either a graded Chen module or a module of this new type.Our characterization of graded primitive ideals of a Leavitt path algebra in terms of the properties of the underlying graph is the main tool for proving the completeness of such classification. We also point out a problem with the characterization of primitive ideals of a Leavitt path algebra in Rangaswamy (2013) [15].     

Response of a Bloch oscillator to a THz-field

In this paper we report on the observation of response of a Bloch oscillator at room temperature to a THz-field of a frequency larger than the Bloch frequency. The oscillator consisted of a semiconductor superlattice structure, with an applied dc voltage giving rise to a dc electron drift current. Submitting the oscillator to a field at a frequency of 3.3 THz caused a sizeable reduction of the current; the THz-field was generated by use of intense THz-radiation pulses focused on an antenna coupled to the superlattice. We attribute the THz-field induced reduction of the current to a frequency modulation of the Bloch oscillations of electrons at the frequency of the THz-field, leading to reduction of the electron drift velocity and, consequently, of the current.     

基于稀疏表示的低比特率可伸缩图像编码算法研究

根据图像的几何结构特性,从人类视觉系统特性出发,建立了Gabor感知多成份字典,进而模拟人类视觉通路的层次处理机制,构建了稀疏编码网络,能够有效去除图像中的高阶冗余,形成更为稀疏的表示。对稀疏表示系数重组后进行比特平面量化,实现了低比特率的可伸缩编码。实验结果表明,在低比特率下,本文算法压缩后重构图像的感知质量要明显优于JPEG2000,峰值信噪比也与其相当,并且对于图像中的边缘和纹理等细节保持效果更佳。     

Symmetries and conservation laws of the damped harmonic oscillator

We work with a formulation of Noether-symmetry analysis which uses the properties of infinitesimal point transformations in the space-time variables to establish the association between symmetries and conservation laws of a dynamical system. Here symmetries are expressed in the form of generators. We have studied the variational or Noether symmetries of the damped harmonic oscillator representing it by an explicitly time-dependent Lagrangian and found that a five-parameter group of transformations leaves the action integral invariant. Amongst the associated conserved quantities only two are found to be functionally independent. These two conserved quantities determine the solution of the problem and correspond to a two-parameter Abelian subgroup.      

Phase State as a Limiting Case of SU（1,1） Coherent State

We show that the Susskind-Glogower phase state is a limiting case of a kind of SU（1,1） coherent states. By analogy, based on the bipartite entangled state representation （ESR） we demonstrate that an appropriate SU（1,1） coherent state composed of the two-mode unitary phase operator e^i also leads to a new phase state in two-mode Fock space, e^i is diagonalized in the ESR.     

基于稀疏表示的谱线自动提取方法

谱线提取在光谱分析中起着非常重要的作用,它对后续的光谱分类和参数测量有着直接的影响。文章提出了一种基于稀疏表示的谱线自动提取方法。首先,用基于稀疏表示的小波去噪方法去除噪声,该方法通过对光谱信号对应的小波系数进行稀疏化处理来达到去噪的目的,其优点是在处理小波系数时虽然将其作为整体进行考虑,但依然能保持小波系数的局部特性不变,所以在去噪的同时很好地保持了特征谱线的信息。其次,利用小波变换与样条拟合相结合的方法拟合出较为满意的伪连续谱,该方法在拟合过程中,先将强谱线扣除掉,从而使得拟合结果非常接近真实的连续谱。最后,通过对归一化后的谱线光谱设置自适应局部阈值来提取特征谱线。实验结果表明该方法切实有效。     

Application of Coordinate-Momentum Intermediate Representation in Solving Eigenstate Problem of a Coupled Oscillator System

We study the eigenstate problem of a kind of coupled oscillators in the new quantum mechanical representation ｜q,μ,υ〉, which is defined as the eigenvector of the operator （μQ ＋ υP）, whereμ and υ are two real parameters. We also use the U operator transformation method to deal with the same problem. We obtain the normally ordered product expressions of U operator and eigenvector. It is shown that the ground state of system Hamiltonian is a squeezed state.     

Establishing path integral in the entangled state representation for Hamiltonians in quantum optics

Based on two mutually conjugate entangled state representations, we establish the path integral formalism for some Hamiltonians of quantum optics in entangled state representations. The Wigner operator in the entangled state representation is presented. Its advantages are explained.     

Density matrix of two interacting particles with kinetic coupling derived in bipartite entangled state representation

A density matrix is usually obtained by solving the Bloch equation, however only a few Hamiltonians' density matrices can be analytically derived. The density matrix for two interacting particles with kinetic coupling is hard to derive by the usual method due to this coupling; this paper solves this problem by using the bipartite entangled state representation.