Search results for "BUNDLES"
showing 10 items of 30 documents
The X-Ray Transform for Connections in Negative Curvature
2016
We consider integral geometry inverse problems for unitary connections and skew-Hermitian Higgs fields on manifolds with negative sectional curvature. The results apply to manifolds in any dimension, with or without boundary, and also in the presence of trapped geodesics. In the boundary case, we show injectivity of the attenuated ray transform on tensor fields with values in a Hermitian bundle (i.e. vector valued case). We also show that a connection and Higgs field on a Hermitian bundle are determined up to gauge by the knowledge of the parallel transport between boundary points along all possible geodesics. The main tools are an energy identity, the Pestov identity with a unitary connect…
On globally generated vector bundles on projective spaces
2009
AbstractA classification is given for globally generated vector bundles E of rank k on Pn having first Chern class c1(E)=2. In particular, we get that they split if k<n unless E is a twisted null-correlation bundle on P3. In view of the well-known correspondence between globally generated vector bundles and maps to Grassmannians, we obtain, as a corollary, a classification of double Veronese embeddings of Pn into a Grassmannian G(k−1,N) of (k−1)-planes in PN.
Purification of Lindblad dynamics, geometry of mixed states and geometric phases
2015
We propose a nonlinear Schr\"odinger equation in a Hilbert space enlarged with an ancilla such that the partial trace of its solution obeys to the Lindblad equation of an open quantum system. The dynamics involved by this nonlinear Schr\"odinger equation constitutes then a purification of the Lindbladian dynamics. This nonlinear equation is compared with other Schr\"odinger like equations appearing in the theory of open systems. We study the (non adiabatic) geometric phases involved by this purification and show that our theory unifies several definitions of geometric phases for open systems which have been previously proposed. We study the geometry involved by this purification and show th…
Refinement and validation of a comprehensive scale for measuring HR practices aimed at performance-enhancement and employee-support
2019
Abstract The purpose of this paper is to refine and validate a Human Resource practices (HRP) scale to measure employees' perceptions and test a two-tier model structured in eight practices and two bundles. In a sample of 554 employees, an EFA (Exploratory Factor Analysis) offered six factors that explained about 70% of the variance. Then, with 1647 employees (from 41 Spanish organizations), first- and second-order models were tested with Confirmatory Factor Analysis (CFA). The former encompasses eight practices. The latter grouped the practices in two bundles, one on enhancing performance and the other on supporting employees. The Cronbach's alpha, Rho coefficient (Composite Reliability Co…
Unirationality of Hurwitz spaces of coverings of degree <= 5
2011
Let $Y$ be a smooth, projective curve of genus $g\geq 1$ over the complex numbers. Let $H^0_{d,A}(Y)$ be the Hurwitz space which parametrizes coverings $p:X \to Y$ of degree $d$, simply branched in $n=2e$ points, with monodromy group equal to $S_d$, and $det(p_{*}O_X/O_Y)$ isomorphic to a fixed line bundle $A^{-1}$ of degree $-e$. We prove that, when $d=3, 4$ or $5$ and $n$ is sufficiently large (precise bounds are given), these Hurwitz spaces are unirational. If in addition $(e,2)=1$ (when $d=3$), $(e,6)=1$ (when $d=4$) and $(e,10)=1$ (when $d=5$), then these Hurwitz spaces are rational.
Ulrich bundles on K3 surfaces
2019
We show that any polarized K3 surface supports special Ulrich bundles of rank 2.
On globally generated vector bundles on projective spaces II
2014
Extending a previous result of the authors, we classify globally generated vector bundles on projective spaces with first Chern class equal to three.
A construction of equivariant bundles on the space of symmetric forms
2021
We construct stable vector bundles on the space of symmetric forms of degree d in n+1 variables which are equivariant for the action of SL_{n+1}(C), and admit an equivariant free resolution of length 2. For n=1, we obtain new examples of stable vector bundles of rank d-1 on P^d, which are moreover equivariant for SL_2(C). The presentation matrix of these bundles attains Westwick's upper bound for the dimension of vector spaces of matrices of constant rank and fixed size.
Big Vector Bundles on Surfaces and Fourfolds
2019
The aim of this note is to exhibit explicit sufficient criteria ensuring bigness of globally generated, rank-$r$ vector bundles, $r \geqslant 2$, on smooth, projective varieties of even dimension $d \leqslant 4$. We also discuss connections of our general criteria to some recent results of other authors, as well as applications to tangent bundles of Fano varieties, to suitable Lazarsfeld-Mukai bundles on four-folds, etcetera.
Register Variation Across English Pharmaceutical Texts: A Corpus-driven Study of Keywords, Lexical Bundles and Phrase Frames in Patient Information L…
2013
Abstract This study constitutes an initial step towards filling a gap in corpus linguistics studies of linguistic and phraseological variation across English pharmaceutical texts, in particular in terms of recurrent linguistic patterns. The study conducted from a register- perspective ( Biber & Conrad, 2009 ), which employs both quantitative and qualitative research procedures, aims to provide a corpus-driven description of vocabulary and phraseology, namely key words, lexical bundles, and phrase frames, used in patient information leaflets and summaries of product characteristics (represented by 463 and 146 texts, respectively) written originally in English and collected in two domain-spec…