Quadrature entanglement and photon-number correlations accompanied by phase-locking

We investigate quantum properties of phase-locked light beams generated in a nondegenerate optical parametric oscillator (NOPO) with an intracavity waveplate. This investigation continuous our previous analysis presented in Phys.Rev.A 69, 05814 (2004), and involves problems of continuous-variable quadrature entanglement in the spectral domain, photon-number correlations as well as the signatures of phase-locking in the Wigner function. We study the role of phase-localizing processes on the quantum correlation effects. The peculiarities of phase-locked NOPO in the self-pulsing instability operational regime are also cleared up. The results are obtained in both the P-representation as a quantum-mechanical calculation in the framework of stochastic equations of motion, and also by using numerical simulation based on the method of quantum state diffusion.Comment: Subm. to PR

Negative Energy Solutions and Symmetries

We revisit the negative energy solutions of the Dirac equation, which become relevant at very high energies and study several symmetries which follow therefrom. The consequences are briefly examined.Comment: 11 pages, Late

Non-perturbative effects in the energy-energy correlation

The fully resummed next-to-leading-order perturbative calculation of the energy-energy correlation in $e^+e^-$ annihilation is extended to include the leading non-perturbative power-behaved contributions computed using the ``dispersive method'' applied earlier to event shape variables. The correlation between a leading (anti)quark and a gluon produces a non-perturbative 1/Q contribution, while non-perturbative effects in the quark-antiquark correlation give rise to a smaller contribution $\ln Q^2/Q^2$. In the back-to-back region, the power-suppressed contributions actually decrease much more slowly, as small non-integer powers of 1/Q, as a result of the interplay with perturbative effects. The hypothesis of a universal low-energy form for the strong coupling relates the coefficients of these contributions to those measured for other observables.Comment: 41 pages, LaTeX, 4 figures, uses JHEP.cl