596 research outputs found
On Nori's Fundamental Group Scheme
We determine the quotient category which is the representation category of
the kernel of the homomorphism from Nori's fundamental group scheme to its
\'etale and local parts. Pierre Deligne pointed out an error in the first
version of this article. We profoundly thank him, in particular for sending us
his enlightning example reproduced in Remark 2.4 2).Comment: 29 page
Characterization of Desulfovibrio giganteus sp. nov., a sulfate-reducing bacterium isolated from a brackish coastal lagoon
In the course of ecological studies in Berre Lagoon, a mediterranean brackish coastal lagoon (Marseille, France), a new slightly halophilic sulfate-reducing bacterium was isolated from anoxic sediments enriched with lactate plus sulfate, and cysteine-HCL as reductant. Because of its morphology and the incomplete oxidation of organic substrates, the isolated strain 8601 was assigned to the genus #Desulfovibrio, resembling #Desulfovibrio gigas. However, it differed from this species in some morphological and physiological characteristics : only one polar flagellum the utilization of methanol, isopropanol, glycerol and cysteine as energy source. Therefore a new species #Desulfovibrio giganteus$ is described. (Résumé d'auteur
On Motives Associated to Graph Polynomials
The appearance of multiple zeta values in anomalous dimensions and
-functions of renormalizable quantum field theories has given evidence
towards a motivic interpretation of these renormalization group functions. In
this paper we start to hunt the motive, restricting our attention to a subclass
of graphs in four dimensional scalar field theory which give scheme independent
contributions to the above functions.Comment: 54
A construction of Frobenius manifolds with logarithmic poles and applications
A construction theorem for Frobenius manifolds with logarithmic poles is
established. This is a generalization of a theorem of Hertling and Manin. As an
application we prove a generalization of the reconstruction theorem of
Kontsevich and Manin for projective smooth varieties with convergent
Gromov-Witten potential. A second application is a construction of Frobenius
manifolds out of a variation of polarized Hodge structures which degenerates
along a normal crossing divisor when certain generation conditions are
fulfilled.Comment: 46 page
Simply connected projective manifolds in characteristic have no nontrivial stratified bundles
We show that simply connected projective manifolds in characteristic
have no nontrivial stratified bundles. This gives a positive answer to a
conjecture by D. Gieseker. The proof uses Hrushovski's theorem on periodic
points.Comment: 16 pages. Revised version contains a more general theorem on torsion
points on moduli, together with an illustration in rank 2 due to M. Raynaud.
Reference added. Last version has some typos corrected. Appears in
Invent.math
PHARAO Laser Source Flight Model: Design and Performances
In this paper, we describe the design and the main performances of the PHARAO
laser source flight model. PHARAO is a laser cooled cesium clock specially
designed for operation in space and the laser source is one of the main
sub-systems. The flight model presented in this work is the first
remote-controlled laser system designed for spaceborne cold atom manipulation.
The main challenges arise from mechanical compatibility with space constraints,
which impose a high level of compactness, a low electric power consumption, a
wide range of operating temperature and a vacuum environment. We describe the
main functions of the laser source and give an overview of the main
technologies developed for this instrument. We present some results of the
qualification process. The characteristics of the laser source flight model,
and their impact on the clock performances, have been verified in operational
conditions.Comment: Accepted for publication in Review of Scientific Instrument
Hirzebruch-Milnor classes and Steenbrink spectra of certain projective hypersurfaces
We show that the Hirzebruch-Milnor class of a projective hypersurface, which
gives the difference between the Hirzebruch class and the virtual one, can be
calculated by using the Steenbrink spectra of local defining functions of the
hypersurface if certain good conditions are satisfied, e.g. in the case of
projective hyperplane arrangements, where we can give a more explicit formula.
This is a natural continuation of our previous paper on the Hirzebruch-Milnor
classes of complete intersections.Comment: 15 pages, Introduction is modifie
Usefulness of two SCAR markers for marker-assisted selection of seedless grapevine cultivars
A PCR-specific marker, SCP18, was developed from a RAPD marker linked to a major locus involved in seedlessness, sdI. A preliminary study of the usefulness of SCP18 and SCC8 (a marker linked to sdI previously developed by LAHOGUE et al. 1998) for the marker assisted selection of seedless varieties was realized using various strategies: a posteriori test in seedless x seedless and seeded x seeded progenies and test of their allelic diversity in a set of 81 seedless and seeded varieties. In contrast to SCP18, SSC8 was found to be a useful marker at least in the seedless x seedless progenies and to show a good linkage disequilibrium with seedlessness in our set of varieties
The Neron-Severi group of a proper seminormal complex variety
We prove a Lefschetz (1,1)-Theorem for proper seminormal varieties over the
complex numbers. The proof is a non-trivial geometric argument applied to the
isogeny class of the Lefschetz 1-motive associated to the mixed Hodge structure
on H^2.Comment: 16 pages; Mathematische Zeitschrift (2008
Chamber basis of the Orlik-Solomon algebra and Aomoto complex
We introduce a basis of the Orlik-Solomon algebra labeled by chambers, so
called chamber basis. We consider structure constants of the Orlik-Solomon
algebra with respect to the chamber basis and prove that these structure
constants recover D. Cohen's minimal complex from the Aomoto complex.Comment: 16 page
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