Tests of local realism versus quantum mechanics based on Bell's inequality employ two entangled qubits. We investigate the general case of two entangled quantum systems defined in N-dimensional Hilbert spaces, or " quNits." Via a numerical linear optimization method we show that violations of local realism are stronger for two maximally entangled quNits ( 3

This paper presents a finding of the correlation between the width of a strong diffuse interstellar band at 6196 Å and the excitation temperature of C 2 based on high resolution and high signal-to-noise ratio spectra. The excitation temperature was determined from absorption lines of the Phillips A 1 Π u − X 1 Σ + g and Mulliken D 1 Σ + u − X 1 Σ + g systems. The width and shape of the narrow 6196 Å DIB profile apparently depend on the C 2 temperature, being broader for higher values.

We show using a numerical approach that gives necessary and sufficient conditions for the existence of local realism, that the bound entangled state presented in Bennett et. al. Phys. Rev. Lett. 82, 5385 (1999) admits a local and realistic description. We also find the lowest possible amount of some appropriate entangled state that must be ad-mixed to the bound entangled state so that the resulting density operator has no local and realistic description and as such can be useful in quantum communication and quantum computation.

We present an analysis of interstellar H 2 toward HD 37903, which is a hot B 1.5 V star located in the NGC 2023 reflection nebula. Meyer et al. (2001, ApJ, 553, L59) used a rich spectrum of vibrationally excited H 2 observed by the HST to calculate a model of the interstellar cloud toward HD 37903. We extend their analysis by including the ν = 0 vibrational level observed by the FUSE satellite. The temperature calculated from the two lowest rotational levels (J = 0, 1) of the H 2 molecule should not be interpreted as a "rotational temperature", but rather as a temperature of thermal equilibrium between the ortho and para H 2 . The ortho-to-para H 2 ratio is lower for the lowest rotational levels than for the higher levels populated by fluorescence. The PDR model of the cloud located in front of HD 37903 points to a gas kinetic temperature ranging from 110 K on the observer side of the cloud to 377 K on the star side. The hydrogen density changes from n H = 1874 cm −3 on the observer side to 544 cm −3 on the star side. The star-cloud distance in our model is 0.45 pc.

A new kind of interstellar cloud is proposed. These are rare (just a few examples among ∼300 lines of sight) objects with the Ca I 4227-Å, Fe I 3720-Å and 3860-Å lines stronger than those of K I (near 7699 Å) and Na I (near 3302 Å). We propose the name 'CaFe' for these clouds. Apparently they occupy different volumes from the well-known interstellar H I clouds where the K I and ultraviolet Na I lines are dominant features. In the CaFe clouds we have not found either detectable molecular features (CH, CN) or diffuse interstellar bands which, as commonly believed, are carried by some complex, organic molecules. We have found the CaFe clouds only along sightlines toward hot, luminous (and thus distant) objects with high rates of mass loss. In principle, the observed gas-phase interstellar abundances reflect the combined effects of the nucleosynthetic history of the material, the depletion of heavy elements into dust grains and the ionization state of these elements which may depend on irradiation by neighbouring stars.