A survey of UV-excess AGNs in the South Galactic Pole

Spectra, position, magnitudes and colors are presented for 485 faint (B<20.5) emission line objects selected with the ultraviolet-excess (UVX) criterion on a area of 24.6 sq. deg in the South Galactic Pole. The objects were selected from the analysis of pixel-to-pixel stacking of COSMOS scans of UKST U, J and R plates. The candidates were observed with the Meudon-ESO Fiber Optics System (MEFOS) at the ESO 3.6m telescope. 429 type 1 AGNs have been identified (373 in the redshift range 0.3<z<2.2). This sample has allowed the measure of a difference on the QSO clustering evolution in comparison with that found for galaxies (La Franca et al 1998). The region is part of the ESO Imaging Survey (EIS) and of the 2dF QSO redshift survey.Comment: 32 pages, 19 figures. To appear on A&AS, revised after minor comment

Causal structure of the entanglement renormalization ansatz

We show that the multiscale entanglement renormalization ansatz (MERA) can be reformulated in terms of a causality constraint on discrete quantum dynamics. This causal structure is that of de Sitter space with a flat spacelike boundary, where the volume of a spacetime region corresponds to the number of variational parameters it contains. This result clarifies the nature of the ansatz, and suggests a generalization to quantum field theory. It also constitutes an independent justification of the connection between MERA and hyperbolic geometry which was proposed as a concrete implementation of the AdS-CFT correspondence

A Technique for the Nondestructive Detection of Voids and Composition Anomalies in Metal Matrix Composite Wires Using X or γ Rays

An initial study of a technique proposed for the nondestructive testing of metal matrix composites is the subject of this paper. These composites are manufactured in the form of approximately 1/2-mm-diameter “precursor” wires. Larger structures are fabricated by diffusion bonding of lay-ups. Reliable nondestructive quality control indicators of wire integrity have not yet been developed although a number of possibilities are being examined.1 Testing of the precursor wires is difficult because current manufacturing processes produce wires that may be entirely satisfactory but that vary in cross-sectional geometry, in surface properties, and sometimes in the amount of matrix material that is present. Techniques based on observations of wire resistance, surface emissivity, and sound emission signatures are difficult to interpret because of these characteristics. Wire imaging using x-ray or neutron techniques is also difficult because large lengths of wire must be examined with a resolution in the plane of the wire exceeding 50 line pairs per millimeter

Conicoid Mirrors

The first order equation relating object and image location for a mirror of arbitrary conic-sectional shape is derived. It is also shown that the parabolic reflecting surface is the only one free of aberration and only in the limiting case of distant sources.Comment: 9 page

The COMBS survey I : Chemical Origins of Metal-Poor Stars in the Galactic Bulge

19 pages, 5 tables, accepted to MNRASChemistry and kinematic studies can determine the origins of stellar population across the Milky Way. The metallicity distribution function of the bulge indicates that it comprises multiple populations, the more metal-poor end of which is particularly poorly understood. It is currently unknown if metal-poor bulge stars ([Fe/H] <−1 dex) are part of the stellar halo in the inner most region, or a distinct bulge population or a combination of these. Cosmological simulations also indicate that the metal-poor bulge stars may be the oldest stars in the Galaxy. In this study, we successfully target metal-poor bulge stars selected using SkyMapper photometry. We determine the stellar parameters of 26 stars and their elemental abundances for 22 elements using R∼ 47 000 VLT/UVES spectra and contrast their elemental properties with that of other Galactic stellar populations. We find that the elemental abundances we derive for our metal-poor bulge stars have lower overall scatter than typically found in the halo. This indicates that these stars may be a distinct population confined to the bulge. If these stars are, alternatively, part of the innermost distribution of the halo, this indicates that the halo is more chemically homogeneous at small Galactic radii than at large radii. We also find two stars whose chemistry is consistent with second-generation globular cluster stars. This paper is the first part of the Chemical Origins of Metal-poor Bulge Stars (COMBS) survey that will chemodynamically characterize the metal-poor bulge population.Peer reviewedFinal Published versio