Rénald David

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We discuss, in terms of the AdS3-CFT2 correspondence, a one-parameter family of (asymptotically AdS3) conical geometries which are generated by point masses and interpolate between AdS3 and BTZ spacetimes. We show that these correspond to spectral flow in N = (4, 4) SCFT2 which interpolate between NS and R sectors. Our method involves representing the(More)
Inorganic compounds made up of low-dimensional ferromagnetic (FM) units display fascinating properties and provide a rich opportunity to investigate FM ground states, fieldinduced transitions, and magnetization steps. Even the spin-valve effect, realized in multilayer thin films, is found in the magnetic metal Ca3Ru2O7 [5] and its Cr-doped analogue in which(More)
BaFe2(PO4)2 was recently prepared by hydrothermal synthesis and identified as the first two-dimensional (2D) Ising ferromagnetic oxide, in which honeycomb layers made up of edge-sharing FeO6 octahedra containing high-spin Fe(2+) ions (S = 2) are isolated by PO4 groups and Ba(2+) cations. BaFe2(PO4)2 has a trigonal R-3 structure at room temperature but(More)
Two new mixed-valence Fe(2/3+) barium phosphates have been synthesized in hydrothermal conditions and characterized: Ba2Fe(2.66+)3(PO4)4·2H2O (compound 1, ratio Fe(3+)/Fe(2+) = 2:1, orthorhombic space group Pbca, a = 6.71240(10) Å, b = 10.6077(2) Å, c = 20.9975(5) Å, R1 = 3.39%) and BaFe(2.33+)3(PO4)3 (compound 2, ratio Fe(3+)/Fe(2+) = 1:2, orthorhombic,(More)
K. Abe,” I. Abt,14 C.J. Ahn,26 T. Akagi,2’ N.J. Allen,4 W.W. Ash,2’,* D. Aston,2’ K.G. Baird,24 C. Baltay,33 H.R. Band,” M.B. Barak&33 G. Baranko,‘O 0. Bardon,‘@ T. Barklow,” A.O. Bazarko,” R. Ben-David,33 A.C. Benvenuti ’ T. Bienz ” G M Bilei ” D Bisello Brau,“’ M. Breidenbach, . I ‘* G. Blaylock,’ J.R. Bogart,z’ T. B&on,” G.R. Bo~er,~’ J.E. ‘27 W.b.(More)
Using an impact parameter tag to select an enriched sample of Z0 → bb events, we have measured the difference between the average charged multiplicity of Z0 → bb and Z0 → hadrons to be nb − nhad = 2.24 ± 0.30(stat.) ± 0.33(syst.) tracks per event. From this, we have derived nb − nuds = 3.31 ± 0.41 ± 0.79. Comparing this measurement with those at lower(More)
The title compound, tetra-sodium hepta-nickel hexa-arsenate, was obtained by ceramic synthesis and crystallizes in the monoclinic space group C2/m. The asymmetric unit contains seven Ni atoms of which two have site symmetry 2/m and three site symmetry 2, four As atoms of which two have site symmetry m and two site symmetry 2, three Na atoms of which two(More)
The crystal structure of the new phase BaCo(II)2(As(III)3O6)2·2(H2O) is built from the stacking of infinite [BaCo2(As3O6)2·H2O] sheets containing ∞[Co(II)O4](6-) chains interconnected by perpendicular ∞[As(III)O2](-) chains. It shows a metamagnetic transition below ∼9 K at a critical field of ∼0.11 T, leading to a moment value of 70% of the expected(More)
The SLD Barrel Cherenkov Ring Imaging Detector was .fully operational in the 1992 physics data run. The electron drift velocity and magnetic field deflection of electron trajectories have been measured. Cherenkov rings have been observed from both the liquid and gas radiators. The number and the resolution of the angle of Cherenkov photons have been(More)
BaFe(2+) 2 (PO4 )2 was recently prepared and identified as the first 2D-Ising ferromagnetic oxide with an original reentrant structural transition driven by high-spin Fe(2+) ions arranged in honeycomb layers. Both long-term air exposure and moderate temperature (T>375 °C) leads to topochemical oxidation into iron-depleted compounds with mixed Fe(2+) /Fe(3+)(More)