296 research outputs found

    Fujita's Conjecture and Frobenius amplitude

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    We prove a version of Fujita's Conjecture in arbitrary characteristic, generalizing results of K.E. Smith. Our methods use the Frobenius morphism, but avoid tight closure theory. We also obtain versions of Fujita's Conjecture for coherent sheaves with certain ampleness properties.Comment: 8 pages. Erratum added to replace Lemma 2.

    Criteria for \sigma-ampleness

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    In the noncommutative geometry of Artin, Van den Bergh, and others, the twisted homogeneous coordinate ring is one of the basic constructions. Such a ring is defined by a σ\sigma-ample divisor, where σ\sigma is an automorphism of a projective scheme X. Many open questions regarding σ\sigma-ample divisors have remained. We derive a relatively simple necessary and sufficient condition for a divisor on X to be σ\sigma-ample. As a consequence, we show right and left σ\sigma-ampleness are equivalent and any associated noncommutative homogeneous coordinate ring must be noetherian and have finite, integral GK-dimension. We also characterize which automorphisms σ\sigma yield a σ\sigma-ample divisor.Comment: 16 pages, LaTeX2e, to appear in J. of the AMS, minor errors corrected (esp. in 1.4 and 3.1), proofs simplifie

    Noncommutative ampleness for multiple divisors

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    The twisted homogeneous coordinate ring is one of the basic constructions of the noncommutative projective geometry of Artin, Van den Bergh, and others. Chan generalized this construction to the multi-homogeneous case, using a concept of right ampleness for a finite collection of invertible sheaves and automorphisms of a projective scheme. From this he derives that certain multi-homogeneous rings, such as tensor products of twisted homogeneous coordinate rings, are right noetherian. We show that right and left ampleness are equivalent and that there is a simple criterion for such ampleness. Thus we find under natural hypotheses that multi-homogeneous coordinate rings are noetherian and have integer GK-dimension.Comment: 11 pages, LaTeX, minor corrections, to appear in J. Algebr

    Ample filters and Frobenius amplitude

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    Let XX be a projective scheme over a field. We show that the vanishing cohomology of any sequence of coherent sheaves is closely related to vanishing under pullbacks by the Frobenius morphism. We also compare various definitions of ample locally free sheaf and show that the vanishing given by the Frobenius morphism is, in a certain sense, the strongest possible. Our work can be viewed as various generalizations of the Serre Vanishing Theorem.Comment: 15 pages, major improvement in results, typo fixed in Equation 2.5, warning footnote added to Lemma 2.

    The Grizzly, October 2, 1990

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    Books Stolen From Students and Professors: Suspect Arrested, 81 Books Confiscated • New Era of Recycling to Change Actions and Minds • Utilities Tunnel Nears Completion • Hardman\u27s Biography of Finney Turns Paperback • Gender Stereotypes by Dr. Englund • Speech Exemption Exam • Stolen Book List • Foreign Spotlight • Ghost Search Continues • AC/DC High Voltage Rock N\u27 Roll • Cop Rock Off-Key • Prince Premier • WVOU Schedule • Medieval Melodies Fill Forum • Homecoming Candidates • Vital Signs of the Trauma Center • Summer Science at Ursinus • Facelift for LSB • Bear Pack Wins Mets • Come Sailing! • Bears Lose 12-7 • Flag Football Kicks Off • Wagner Takes First in Mets Meet • US Must Aid Soviet Economic Woes • Temple Strike: Avoiding The Real Issue • Letters: Doughty Appreciates Grizzly; Wall Destruction Coincidental? • Soccer Working Hard • Hockey Splitshttps://digitalcommons.ursinus.edu/grizzlynews/1259/thumbnail.jp

    Standalone vertex finding in the ATLAS muon spectrometer

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    A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011

    Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

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    Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson

    Measurement of the top quark pair cross section with ATLAS in pp collisions at √s=7 TeV using final states with an electron or a muon and a hadronically decaying τ lepton

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    A measurement of the cross section of top quark pair production in proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 7 TeV is reported. The data sample used corresponds to an integrated luminosity of 2.05 fb -1. Events with an isolated electron or muon and a τ lepton decaying hadronically are used. In addition, a large missing transverse momentum and two or more energetic jets are required. At least one of the jets must be identified as originating from a b quark. The measured cross section, σtt-=186±13(stat.)±20(syst.)±7(lumi.) pb, is in good agreement with the Standard Model prediction

    Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

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    A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN
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