126,512 research outputs found
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 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 . 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
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