Structural properties and quasiparticule energies of cubic SrO, MgO and SrTiO3

The structural properties and the band structures of the charge-transfer insulating oxides SrO, MgO and SrTiO3 are computed both within density functional theory in the local density approximation (LDA) and in the Hedin's GW scheme for self-energy corrections, by using a model dielectric function, which approximately includes local field and dynamical effects. The deep valence states are shifted by the GW method to higher binding energies, in very good agreement with photoemission spectra. Since in all of these oxides the direct gaps at high-symmetry points of the Brillouin zone may be very sensitive to the actual value of the lattice parameter a, already at the LDA level, self-energy corrections are computed both at the theoretical and the experimental a. For MgO and SrO, the values of the transition energies between the valence and the conduction bands are improved by GW corrections, while for SrTiO3 they are overestimated. The results are discussed in relation to the importance of local field effects and to the nature of the electronic states in these insulating oxides.Comment: 3 figures, accepted in J. Phys.: Condens. Matte

Cryogenic cooling study for the advanced limb scanner

The cryogenic operating requirements for a VM refrigerator to be used for detector cooling of the advanced limb scanner (ALS) instrument are defined. Determination of these requirements include consideration of mission and environmental constraints. Based on the operating requirements a detailed refrigerator design and performance analysis is conducted resulting in an optimized VM refrigerator conceptual design. The cooler-instrument-spacecraft interfaces are evaluated resulting in recommendations as to the best approach and most effective concepts resulting in simple and satisfactory interfaces. A preliminary implementation plan and schedule describing the general tasks required to develop, design, manufacture, test, and deliver three VM coolers and required support equipment to support an ALS flight experiment are presented. The result of this effort shows that existing VM cooler technology is sufficient to satisfy ALS mission requirements and schedules

Model of black hole evolution

From the postulate that a black hole can be replaced by a boundary on the apparent horizon with suitable boundary conditions, an unconventional scenario for the evolution emerges. Only an insignificant fraction of energy of order $(mG)^{-1}$ is radiated out. The outgoing wave carries a very small part of the quantum mechanical information of the collapsed body, the bulk of the information remaining in the final stable black hole geometry.Comment: 9 pages, harvmac, 3 figures, minor addition

Model of black hole evolution

From the postulate that a black hole can be replaced by a boundary on the apparent horizon with suitable boundary conditions, an unconventional scenario for the evolution emerges. Only an insignificant fraction of energy of order $(mG)^{-1}$ is radiated out. The outgoing wave carries a very small part of the quantum mechanical information of the collapsed body, the bulk of the information remaining in the final stable black hole geometry.Comment: 9 pages, harvmac, 3 figures, minor addition

Carbon-atom wires produced by nanosecond pulsed laser deposition in a background gas

Wires of sp-hybridized carbon atoms are attracting interest for both fundamental aspects of carbon science and for their appealing functional properties. The synthesis by physical vapor deposition has been reported to provide sp-rich carbon films but still needs to be further developed and understood in detail. Here the synthesis of carbon-atom wires (CAWs) has been achieved by nanosecond pulsed laser deposition (PLD) expoliting the strong out-of-equilibrium conditions occurring when the ablation plasma is confined in a background gas. Surface Enhnaced Raman scattering (SERS) spectra of deposited films indicates that CAWs are mixed with a mainly $sp^2$ amorphous carbon in a $sp-sp^2$ hybrid material. Optimal conditions for the deposition of sp-carbon phase have been investigated by changing deposition parameters thus suggesting basic mechanisms of carbon wires formation. Our proof-of-concept may open new perspectives for the targeted fabrication of CAWs and $sp-sp^2$ structures.Comment: 15 pages 4 figure

The perception of instability and legitimacy of status differences enhances the infrahumanization bias among high status groups

Previous research within the social identity framework has shown that perceptions of legitimacy and stability of status differences interactively determine cognitive, emotional, and behavioural responses to intergroup contexts. Whether such perceptions affect subtle forms of prejudice, namely infrahumanisation, is unknown. We examined if the perceptions regarding high status stability and legitimacy are associated to the infrahumanisation bias. We hypothesized that participants perceiving status differences as unstable and legitimate would report higher levels of infrahumanization than those who perceive status differences as stable and/or illegitimate. Participants (N = 439 Italian students enrolled in psychology courses) completed a structured paper-and-pencil questionnaire. We found that participants tended to attribute more negative secondary emotions to their ingroup (Italians) than to the outgroup (immigrants from Africa), indicating the presence of an infrahumanization bias. The results of a moderated regression aimed at predicting infrahumanization showed that high-status group members who perceived status differences as legitimate and unstable reported higher levels of infrahumanization than their counterparts did. The results attest the important and independent role of the perceptions related to the status for the debate on intergroup relations

Two Dimensional Quantum Dilaton Gravity and the Positivity of Energy

Using an argument due to Regge and Teitelboim, an expression for the ADM mass of 2d quantum dilaton gravity is obtained. By evaluating this expression we establish that the quantum theories which can be written as a Liouville-like theory, have a lower bound to energy, provided there is no critical boundary. This fact is then reconciled with the observation made earlier that the Hawking radiation does not appear to stop. The physical picture that emerges is that of a black hole in a bath of quantum radiation. We also evaluate the ADM mass for the models with RST boundary conditions and find that negative values are allowed. The Bondi mass of these models goes to zero for large retarded times, but becomes negative at intermediate times in a manner that is consistent with the thunderpop of RST.Comment: 16 pages, phyzzx, COLO-HEP-309. (Confusing points in previous version clarified, discussion of ADM and Bondi masses in RST case added.