A refined stable restriction theorem for vector bundles on quadric threefolds

Let E be a stable rank 2 vector bundle on a smooth quadric threefold Q in the projective 4-space P. We show that the hyperplanes H in P for which the restriction of E to the hyperplane section of Q by H is not stable form, in general, a closed subset of codimension at least 2 of the dual projective 4-space, and we explicitly describe the bundles E which do not enjoy this property. This refines a restriction theorem of Ein and Sols [Nagoya Math. J. 96, 11-22 (1984)] in the same way the main result of Coanda [J. reine angew. Math. 428, 97-110 (1992)] refines the restriction theorem of Barth [Math. Ann. 226, 125-150 (1977)].Comment: Ann. Mat. Pura Appl. 201

Nanosized superconducting constrictions

Nanowires of lead between macroscopic electrodes are produced by means of an STM. Magnetic fields may destroy the superconductivity in the electrodes, while the wire remains in the superconducting state. The properties of the resulting microscopic Josephson junctions are investigated.Comment: 3 pages,3 eps figures include

Mesoscopic superconductors in the London limit: equilibrium properties and metastability

We present a study of the behaviour of metastable vortex states in mesoscopic superconductors. Our analysis relies on the London limit within which it is possible to derive closed analytical expressions for the magnetic field and the Gibbs free energy. We consider in particular the situation where the vortices are symmetrically distributed along a closed ring. There, we obtain expressions for the confining Bean-Livingston barrier and for the magnetization which turns out to be paramagnetic away from thermodynamic equilibrium. At low temperature, the barrier is high enough for this regime to be observable. We propose also a local description of both thermodynamic and metastable states based on elementary topological considerations; we find structural phase transitions of vortex patterns between these metastable states and we calculate the corresponding critical fields.Comment: 24 pages, 20 figure

Complete intersections: Moduli, Torelli, and good reduction

We study the arithmetic of complete intersections in projective space over number fields. Our main results include arithmetic Torelli theorems and versions of the Shafarevich conjecture, as proved for curves and abelian varieties by Faltings. For example, we prove an analogue of the Shafarevich conjecture for cubic and quartic threefolds and intersections of two quadrics.Comment: 37 pages. Typo's fixed. Expanded Section 2.

Flux-Induced Vortex in Mesoscopic Superconducting Loops

We predict the existence of a quantum vortex for an unusual situation. We study the order parameter in doubly connected superconducting samples embedded in a uniform magnetic field. For samples with perfect cylindrical symmetry, the order parameter has been known for long and no vortices are present in the linear regime. However, if the sample is not symmetric, there exist ranges of the field for which the order parameter vanishes along a line, parallel to the field. In many respects, the behavior of this line is qualitatively different from that of the vortices encountered in type II superconductivity. For samples with mirror symmetry, this flux-induced vortex appears at the thin side for small fluxes and at the opposite side for large fluxes. We propose direct and indirect experimental methods which could test our predictions.Comment: 6 pages, Latex, 4 figs., uses RevTex, extended to situations far from cylindrical symmetr

Giant vortex state in perforated aluminum microsquares

We investigate the nucleation of superconductivity in a uniform perpendicular magnetic field H in aluminum microsquares containing a few (2 and 4) submicron holes (antidots). The normal/superconducting phase boundary T_c(H) of these structures shows a quite different behavior in low and high fields. In the low magnetic field regime fluxoid quantization around each antidot leads to oscillations in T_c(H), expected from the specific sample geometry, and reminiscent of the network behavior. In high magnetic fields, the T_c(H) boundaries of the perforated and a reference non-perforated microsquare reveal cusps at the same values of Phi/Phi_0 (where Phi is the applied flux threading the total square area and Phi_0 is the superconducting flux quantum), while the background on T_c(H) becomes quasi-linear, indicating that a giant vortex state is established. The influence of the actual geometries on T_c(H) is analyzed in the framework of the linearized Ginzburg-Landau theory.Comment: 14 pages, 6 PS figures, RevTex, accepted for publication in Phys. Rev.

CENSORS: A Combined EIS-NVSS Survey Of Radio Sources. I. Sample definition, radio data and optical identifications

A new sample of radio sources, with the designated name CENSORS (A Combined EIS-NVSS Survey Of Radio Sources), has been defined by combining the NRAO VLA Sky Survey (NVSS) at 1.4 GHz with the ESO Imaging Survey (EIS) Patch D, a 3 by 2 degree region of sky centred at 09 51 36.0, -21 00 00 (J2000). New radio observations of 199 NVSS radio sources with NVSS flux densities S(1.4GHz) > 7.8mJy are presented, and compared with the EIS I-band imaging observations which reach a depth of I~23; optical identifications are obtained for over two-thirds of the ~150 confirmed radio sources within the EIS field. The radio sources have a median linear size of 6 arcseconds, consistent with the trend for lower flux density radio sources to be less extended. Other radio source properties, such as the lobe flux density ratios, are consistent with those of brighter radio source samples. From the optical information, 30-40% of the sources are expected to lie at redshifts z >~ 1.5. One of the key goals of this survey is to accurately determine the high redshift evolution of the radio luminosity function. These radio sources are at the ideal flux density level to achieve this goal; at redshifts z~2 they have luminosities which are around the break of the luminosity function and so provide a much more accurate census of the radio source population at those redshifts than the existing studies of extreme, high radio power sources. Other survey goals include investigating the dual--population unification schemes for radio sources, studying the radio luminosity dependence of the evolution of radio source environments, and understanding the radio power dependence of the K-z relation for radio galaxies.Comment: Accepted for publication in MNRAS. 28 pages plus 36 reduced resolution jpeg figures. A postscript version with full resolution figures included in the text is available from http://www.roe.ac.uk/~pnb/censors.ps.g

The VIMOS-VLT Deep Survey. The dependence of clustering on galaxy stellar mass at z~1

Aims: We use the VVDS-Deep first-epoch data to measure the dependence of galaxy clustering on galaxy stellar mass, at z~0.85. Methods: We measure the projected correlation function wp(rp) for sub-samples with 0.5<z<1.2 covering different mass ranges between 10^9 and 10^11 Msun. We quantify in detail the observational selection biases using 40 mock catalogues built from the Millennium run and semi-analytic models. Results: Our simulations indicate that serious incompleteness in mass is present only for log(M/Msun)<9.5. In the mass range log(M/Msun)=[9.0-9.5], the photometric selection function of the VVDS misses 2/3rd of the galaxies. The sample is virtually 100% complete above 10^10 Msun. We present the first direct evidence for a clear dependence of clustering on the galaxy stellar mass at z~0.85. The clustering length increases from r0 ~ 2.76 h^-1 Mpc for galaxies with mass M>10^9 Msun to r0 ~ 4.28 h^-1 Mpc for galaxies more massive than 10^10.5 Msun. At the same time, the slope increases from ~ 1.67 to ~ 2.28. A comparison of the observed wp(rp) to local measurements by the SDSS shows that the evolution is faster for objects less massive than ~10^10.5 Msun. This is interpreted as a higher dependence on redshift of the linear bias b_L for the more massive objects. While for the most massive galaxies b_L decreases from 1.5+/-0.2 at z~0.85 to 1.33+/-0.03 at z~0.15, the less massive population maintains a virtually constant value b_L~1.3. This result is in agreement with a scenario in which more massive galaxies formed at high redshift in the highest peaks of the density field, while less massive objects form at later epochs from the more general population of dark-matter halos.Comment: 13 pages, 10 figures, accepted in A&

Conclusions and recommendations of a who expert consultation meeting on iron supplementation for infants and young children in malaria endemic areas [Conclusions et recommandations à l\u27issue de la consultation de l\u27oms sur la lutte contre la carence martiale chez le nourrisson et le jeune enfant dans les pays d\u27endémie palustre]

This article presents the results of an expert consultation meeting aimed at evaluating the safety and public health implications of administering supplemental iron to infants and young children in malaria-endemic areas. Participants at this meeting that took place in Lyon, France on June 12-14, 2006 reached consensus on several important issues related to iron supplementation for infants and young children in malaria-endemic areas. The conclusions in this report apply specifically to regions where malaria is endemic