One-body density matrix and momentum distribution in s-p and s-d shell nuclei

Analytical expressions of the one- and two- body terms in the cluster expansion of the one-body density matrix and momentum distribution of the s-p and s-d shell nuclei with Ν — Ζ are derived. They depend on the harmonic oscillator parameter b and the parameter β which originates from the Jastrow correlation function. These parameters have been determined .by least squares fit to the experimental charge form factors. The inclusion of short-range correlations increases the high momentum component of the momentum distribution, 7i(k) for all nuclei we have considered while there is an A dependence of ra(k) both at small values of k and the high momentum component. The A dependence of the high momentum com- . ponent of n(k) becomes quite small when the nuclei 24Mg, 28Si and 32S are treated as ld-2s shell nuclei having the occupation probability of the 2s-state as an extra free parameter in the fit to the form factors

Quantum backflow effect and nonclassicality

The quantum backflow effect is a counterintuitive behavior of the probability current of a free particle, which may be negative even for states with vanishing negative momentum component. Here, we address the notion of nonclassicality arising from the backflow effect, i.e. from the negativity of the probability current, and analyze its relationships with the notion of nonclassicality based on the negativity of the Wigner function. Our results show that backflow is linked to a different, and in fact more restrictive, notion of nonclassicality, the negativity of the Wigner function being only a necessary prerequisite for its occurrence. This hierarchical structure may be confirmed by looking at the addition of thermal noise, which more easily destroys the negativity of the probability current than the negativity of the Wigner function itself.

Anomalous Annihilation of Positrons in Several Solid Hydrocarbons

In previous experiments with positrons annihilating in liquid organic materials (Hogg et al.) the measurements of IN (intensity of the low momentum component from angular correlation data) and I2 (intensity of the long lived component from lifetime measurements) have resulted in IN = I2/3 within experimental error.For samples of CH4, C6H6, and C6H12 measurements in the liquid state yield the expected equality between IN and I2/3. However, in the solid state for these substances there is a marked disagreement between IN and I2/3. The value of IN, in all cases, is essentially zero suggesting that no positronium is formed, but the value of I2 remains large.