Minimum Detection Efficiencies for a Loophole-Free Bell-type Test

We discuss the problem of finding the most favorable conditions for closing the detection loophole in a test of local realism with a Bell inequality. For a generic non-maximally entangled two-qubit state and two alternative measurement bases we apply Hardy's proof of non-locality without inequality and derive an Eberhard-like inequality. For an infinity of non-maximally entangled states we find that it is possible to refute local realism by requiring perfect detection efficiency for only one of the two measurements: the test is free from the detection loophole for any value of the detection efficiency corresponding to the other measurement. The maximum tolerable noise in a loophole-free test is also evaluated.Comment: 4 pages, 2 figure

Reclaiming martyrdom: Augustine\u27s reconstruction of martyrdom in late antique North Africa

The cult of martyrs existed throughout the Mediterranean world in late antiquity, but local communities venerated the martyrs in their own ways and for their own reasons. During the fourth and fifth centuries, two factions of Christianity existed in North Africa. Catholicism and Donatism competed for the souls of North African Christians, and this competition influenced the development of the cult of martyrs in that region. The sermons on the martyrs by Augustine of Hippo (354-430) illuminate the milieu of North African Christianity\u27s cult of martyrs and demonstrate that Augustine viewed possessing the martyrs as a key component in overcoming his ecclesiastical rivals. In order to reclaim martyrdom from the Donatists, Augustine reinterpreted martyrdom solely in light of the New Testament concept of bearing witness. This reinterpretation had a number of results. First, focusing on witness bearing gave Augustine the justification for invalidating all forms of voluntary martyrdom, which the Donatists tolerated. Secondly, Augustine taught that Christians must not admire the sufferings of martyrs for their own sakes; they must look past the sufferings to honor the cause of the martyrs, which belonged to the Catholics. Third, Augustine\u27s emphasis on the martyrs\u27 cause over the martyrs\u27 sufferings enabled him to expand the classification of martyr well beyond those who had died violently for the faith. This approach to understanding the cult of martyrs demonstrates the unique manner in which one bishop attempted to make the cult relevant to his local circumstances

Multiple high-pressure phase transitions in BiFeO3

We investigate the high-pressure phase transitions in BiFeO3 by single crystal and powder x-ray diffraction, as well as single crystal Raman spectroscopy. Six phase transitions are reported in the 0-60 GPa range. At low pressures, up to 15 GPa, 4 transitions are evidenced at 4, 5, 7 and 11 GPa. In this range, the crystals display large unit cells and complex domain structures, which suggests a competition between complex tilt systems and possibly off-center cation displacements. The non polar Pnma phase remains stable over a large pressure range between 11 and 38 GPa, where the distortion (tilt angles) changes only little with pressure. The two high-pressure phase transitions at 38 and 48 GPa are marked by the occurence of larger unit cells and an increase of the distorsion away from the cubic parent perovskite cell. We find no evidence for a cubic phase at high pressure, nor indications that the structure tends to become cubic. The previously reported insulator-to-metal transition at 50 GPa appears to be symmetry breaking.Comment: 11 pages, 8 figure

Theoretical search for superconductivity in Sc3XB perovskites and weak ferromagnetism in Sc3X (X = Tl, In, Ga, Al)

A possibility for a new family of intermetallic perovskite superconductors Sc3XB, with X = Tl, In, Ga and Al, is presented as a result of KKR electronic structure and pseudopotential phonon calculations. The large values of computed McMillan--Hopfield parameters on scandium suggest appearance of superconductivity in Sc3XB compounds. On the other hand, the possibility of weak itinerant ferromagnetic behavior of Sc3X systems is indicated by the small magnetic moment on Sc atoms in two cases of X =~ l and In. Also the electronic structure and resulting superconducting parameters for more realistic case of boron--deficient systems Sc3XB_x are computed using KKR--CPA method, by replacing boron atom with a vacancy. The comparison of the calculated McMillan--Hopfield parameters of the Sc3XB series with corresponding values in MgCNi3 and YRh3B superconductors is given, finding the favorable trends for superconductivity.Comment: 13 pages, 13 figures. v3 - revise