6,149 research outputs found
Electromagnetic radiation of baryons containing two heavy quarks
The two heavy quarks in a baryon which contains two heavy quarks and a light
one, can constitute a scalar or axial vector diquark. We study electromagnetic
radiations of such baryons, (i) \Xi_{(bc)_1} -> \Xi_{(bc)_0}+\gamma, (ii)
\Xi_{(bc)_1}^* -> \Xi_{(bc)_0}+\gamma, (iii) \Xi_{(bc)_0}^{**}(1/2, l=1) ->
\Xi_{(bc)_0}+\gamma, (iv) \Xi_{(bc)_0}^{**}(3/2, l=1) -> \Xi_{(bc)_0}+\gamma
and (v) \Xi_{(bc)_0}^{**}(3/2, l=2) -> \Xi_{(bc)_0}+\gamma, where
\Xi_{(bc)_{0(1)}}, \Xi^*_{(bc)_1} are S-wave bound states of a heavy scalar or
axial vector diquark and a light quark, and \Xi_{(bc)_0}^{**}(l is bigger than
1) are P- or D-wave bound states of a heavy scalar diquark and a light quark.
Analysis indicates that these processes can be attributed into two categories
and the physical mechanisms which are responsible for them are completely
distinct. Measurements can provide a good judgment for the diquark structure
and better understanding of the physical picture.Comment: 15 pages, Late
Quantum State Transfer Characterized by Mode Entanglement
We study the quantum state transfer (QST) of a class of tight-bonding Bloch
electron systems with mirror symmetry by considering the mode entanglement.
Some rigorous results are obtained to reveal the intrinsic relationship between
the fidelity of QST and the mirror mode concurrence (MMC), which is defined to
measure the mode entanglement with a certain spatial symmetry and is just the
overlap of a proper wave function with its mirror image. A complementarity is
discovered as the maximum fidelity is accompanied by a minimum of MMC. And at
the instant, which is just half of the characteristic time required to
accomplish a perfect QST, the MMC can reach its maximum value one. A large
class of perfect QST models with a certain spectrum structure are discovered to
support our analytical results.Comment: 6 pages, 3 figures. to appear in PR
Velocity control of longitudinal vibration ultrasonic motor using improved Elman neural network trained by CQPSO with Lévy flights
Longitudinally vibration ultrasonic motor (LV-USM), a canonical nonlinear system, utilizes the inverse piezoelectric effect of piezoelectric ceramic to generate the mechanical vibration within the scope of ultrasonic frequency. However, it is very difficult to establish a strict and accurate mathematical model. Hence seeking a dynamic identifier and controller for LV-USM avoiding the accurate mathematical model becomes a feasible approach. In this paper, a novel learning algorithm for dynamic recurrent Elman neural networks is present based on a particle swarm optimization (PSO) to identify and control an LV-USM. To overcome the PSO’s global search ability, Lévy flights, a kind of random walks, are imported to improve the ability of exploration rather than Brownian motion or Gauss disturbance based on Cooperative Quantum-behaved PSO (CQPSO). Thereafter, a controller is designed to perform speed control for LV-USM along with the nonlinear identification also using this kind of neural network. By discrete Lyapunov stability approach, the controller is proven to be stable theoretically and the latter trial shows its robustness of anti-noise performance. In the experiments, the numerical results illustrate that the designed identifier and controller can achieve both higher convergence precision and speed, relative to current state-of-the-art other methods. Moreover, this controller shows lower control error than other approaches while the displacement of the rotor disc in LV-USM appears more smooth and uniform
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