Symmetry restoration and quantumness reestablishment

A realistic quantum many-body system, characterized by a generic microscopic Hamiltonian, is accessible only through approximation methods. The mean field theories, as the simplest practices of approximation methods, commonly serve as a powerful tool, but unfortunately often violate the symmetry of the Hamiltonian. The conventional BCS theory, as an excellent mean field approach, violates the particle number conservation and completely erases quantumness characterized by concurrence and quantum discord between different modes. We restore the symmetry by using the projected BCS theory and the exact numerical solution and find that the lost quantumness is synchronously reestablished. We show that while entanglement remains unchanged with the particle numbers, quantum discord behaves as an extensive quantity with respect to the system size. Surprisingly, discord is hardly dependent on the interaction strengths. The new feature of discord offers promising applications in modern quantum technologies.Comment: 17 pages and 3 figure

Possible Σ(12−)\Sigma({1\over2}^-) under the Σ∗(1385)\Sigma^*(1385) peak in KΣ∗K\Sigma^* photoproduction

The LEPS collaboration has recently reported a measurement of the reaction $\gamma n\to K^+\Sigma^{*-}(1385)$ with linearly polarized photon beam at resonance region. The observed beam asymmetry is sizably negative at $E_\gamma=1.8-2.4 \mathrm{GeV}$, in contrast to the presented theoretical prediction. In this paper, we calculate this process in the framework of the effective Lagrangian approach. By including a newly proposed $\Sigma(J^P={1\over2}^-)$ state with mass around 1380~MeV, the experimental data for both $\gamma n$ and $\gamma p$ experiments can be well reproduced. It is found that the $\Sigma({1\over2}^-)$ and/or the contact term may play important role and deserve further investigation.Comment: modified version to be published at Phys. Rev.

Extreme Learning Machine Based Non-Iterative and Iterative Nonlinearity Mitigation for LED Communications

This work concerns receiver design for light emitting diode (LED) communications where the LED nonlinearity can severely degrade the performance of communications. We propose extreme learning machine (ELM) based non-iterative receivers and iterative receivers to effectively handle the LED nonlinearity and memory effects. For the iterative receiver design, we also develop a data-aided receiver, where data is used as virtual training sequence in ELM training. It is shown that the ELM based receivers significantly outperform conventional polynomial based receivers; iterative receivers can achieve huge performance gain compared to non-iterative receivers; and the data-aided receiver can reduce training overhead considerably. This work can also be extended to radio frequency communications, e.g., to deal with the nonlinearity of power amplifiers

Composite Rotor Blade Design Optimization for Vibration Reduction with Aeroelastic Constraints

AbstractThe paper presents an analytical study of the helicopter rotor vibratory load reduction design optimization with aeroelastic stability constraints. The composite rotor blade is modeled by beam type finite elements, and warping deformation is taken into consideration for 2 dimension analysis, while the one-dimension nonlinear differential equations of blade motion are formulated via Hamilton's principle. The rotor hub vibratory loads is chosen as the objective function, while rotor blade section construction parameter, composite material ply structure and blade tip swept angle as the design variables, and autorotation inertia, natural frequency and aeroelastic stability as the constraints. A 3 bladed rotor is designed, as an example, based on the vibratory hub load reduction optimization process with swept tip angle and composite material. The calculating results show a 24. 9%-33% reduction of 3/rev hub loads in comparison with the base-line rotor