π0→γ∗γ\pi^0\to\gamma^*\gamma transition form factor within Light Front Quark Model

We study the transition form factor of $\pi^0\to\gamma^* \gamma$ as a function of the momentum transfer $Q^2$ within the light-front quark model (LFQM). We compare our result with the experimental data by BaBar as well as other calculations based on the LFQM in the literature. We show that our predicted form factor fits well with the experimental data, particularly those at the large $Q^2$ region.Comment: 11 pages, 4 figures, accepted for publication in PR

Proton-Antiproton Annihilation in Baryonium

A possible interpretation of the near-threshold enhancement in the $(p\bar{p})$-mass spectrum in $J/\psi{\to}\gamma p{\bar p}$ is the of existence of a narrow baryonium resonance X(1860). Mesonic decays of the $(p\bar{p})$-bound state X(1860) due to the nucleon-antinucleon annihilation are investigated in this paper. Mesonic coherent states with fixed $G$-parity and $P$-parity have been constructed . The Amado-Cannata-Dedoder-Locher-Shao formulation(Phys Rev Lett. {\bf 72}, 970 (1994)) is extended to the decays of the X(1860). By this method, the branch-fraction ratios of $Br(X\to \eta 4\pi)$, $Br(X\to \eta 2\pi)$ and $Br(X\to 3\eta)$ are calculated. It is shown that if the X(1860) is a bound state of $(p\bar{p})$, the decay channel ($X\to \eta 4\pi)$ is favored over $(X\to \eta 2\pi)$. In this way, we develop criteria for distinguishing the baryonium interpretation for the near-threshold enhancement effects in $(p\bar{p})$-mass spectrum in $J/\psi{\to}\gamma p{\bar p}$ from other possibilities. Experimental checks are expected. An intuitive picture for our results is discussed.Comment: 19 pages, 3 figure

Structural relaxation in a system of dumbbell molecules

The interaction-site-density-fluctuation correlators, the dipole-relaxation functions, and the mean-squared displacements of a system of symmetric dumbbells of fused hard spheres are calculated for two representative elongations of the molecules within the mode-coupling theory for the evolution of glassy dynamics. For large elongations, universal relaxation laws for states near the glass transition are valid for parameters and time intervals similar to the ones found for the hard-sphere system. Rotation-translation coupling leads to an enlarged crossover interval for the mean-squared displacement of the constituent atoms between the end of the von Schweidler regime and the beginning of the diffusion process. For small elongations, the superposition principle for the reorientational $\alpha$-process is violated for parameters and time intervals of interest for data analysis, and there is a strong breaking of the coupling of the $\alpha$-relaxation scale for the diffusion process with that for representative density fluctuations and for dipole reorientations.Comment: 15 pages, 14 figures, Phys. Rev. E in pres

A Single-Stage Z-source Inverter for Transformerless Grid Connection with a Proportional-Resonant Controller for DC Current Elimination

The ever-rising number of grid-connected inverters contributes to an increase of DC current injection into utility grid, resulting in the saturation of distribution transformers, metering errors and the corrosion of earthling conductors. A transformerless single-stage Z-source inverter uses only two switching devices in its converter circuit to generate sinusoidal voltage as that of a full-bridge inverter. However, this inverter has the problem of having a DC offset in the AC waveform due to the presence of steady-state error when the modulation index is varied. The paper proposes a Proportional-Resonant (PR) control scheme to eliminate this DC offset. By comparing Z-source inverter output voltage with the sinusoidal reference voltage obtained from the sinusoidal control signal, an error signal is obtained which is fed into the PR controller. An infinite gain at the fundamental frequency is introduced by the PR controller, thus achieving zero steady-state error resulting in the elimination of DC current injection into the utility grid. This method does not depend on high-precision current measurement or the use of coupled inductors. Also, this method can be used to improve power quality by providing reactive power compensation to the load at the point of common coupling. Simulation results are presented to confirm that this simple, cost-effective method can be used to eliminate DC current injection for different values of modulation index without compromising the dynamic response of the current feedback loo

Càdlàg rough differential equations with reflecting barriers

We investigate rough differential equations with a time-dependent reflecting lower barrier, where both the driving (rough) path and the barrier itself may have jumps. Assuming the driving signals allow for Young integration, we provide existence, uniqueness and stability results. When the driving signal is a càdlàg p-rough path for p ∈ [2, 3), we establish existence to general reflected rough differential equations, as well as uniqueness in the one-dimensional case