2,280 research outputs found
Artin groups associated to infinite Coxeter groups
No full textAbstractFirst we remark that the cellular complex constructed by Salvetti (1994) can be considered as a ‘topological’ invariant of a graph, so its cohomology is also an invariant. We use the construction of Salvetti (1994) to calculate the cohomology of the Artin group associated to the complete graph Kn, using coefficients in a local system over Z[q,q−1]. The standard cohomology over Z is obtained by specializing q to 1. While doing such computations, we obtain also an explicit rational function for the Poincaré series of the Coxeter group associated to Kπ, and note that it has exponential growth for n⩾4
The Morse complex of a line arrangement
No full textLet M(A) be the complement in C2 of a complexified line arrangement. We provide compact formulas for a Morse complex which computes the (co)homology of M(A) with coefficients in an abelian local system. This refines and simplifies, in the two-dimensional case, a general construction appeared in [M. Salvetti, S. Settepanella, Combinatorial Morse theory and minimality of hyperplane arrangements, Geom. Topol. 11 (2007) 1733–1766], giving also a direct geometrical interpretation
Corrigendum: A Perspective of Coagulation Dysfunction in Multiple Sclerosis and in Experimental Allergic Encephalomyelitis
No full textIn the published article, there was an error regarding the affiliations for Marco Salvetti. As well as having affiliation “3,” he should also have “IRCCS Istituto Neurologico Mediterraneo (INM) Neuromed, Pozzilli, Italy.” There was also an omission in the affiliation for Tatiana Koudriavtseva. Instead of “Department of Clinical Experimental Oncology, Regina Elena National Cancer Institute, Rome, Italy”, it should be “Department of Clinical Experimental Oncology, IRCCS Regina Elena National Cancer Institute, Rome, Italy”. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated. Copyright © 2019 Plantone, Inglese, Salvetti and Koudriavtsev
Numerical Simulation of Cavitating Flows in Complex Geometries
No full textThe present contribution focusses on numerical simulation of cavitating flows in complex geometry. We consider compressible flows and cavitation models assuming a homogeneous barotropic flow behavior. Different numerical issues are analyzed and possible solutions are presented and validated. Finally, an application to the simulation of the flow in a real turbopump inducer designed for liquid propelled rockets is presented
Combinatorial Morse theory and minimality of hyperplane arrangements
No full textUsing combinatorial Morse theory on the CW-complex S constructed in Salvetti [15] which gives the homotopy type of the complement to a complexified real arrangement of hyperplanes, we find an explicit combinatorial gradient vector field on S, such that S contracts over a minimal CW-complex. The existence of such minimal complex was proved before Dimca and Padadima [5] and Randell [14] and there exists also some description of it by Yoshinaga [19]. Our description seems much more explicit and allows to find also an algebraic complex computing local system cohomology, where the boundary operator is effectively computable
The cohomology of the braid group and of with coefficients in a geometric representation
No full textThis article is a short version of a paper which addresses the cohomology of the third braid group and of with coefficients in geometric representations.We give precise statements of the results, some tools and some proofs, avoiding very technical computations here
Preface
No full textIntroduction to the proceedings of the 12th instalment in the bi-annual Workshop series on Direct and Large Eddy Simulation (DLES), held in Madrid on June 5–7, 2019
Multimodal retinal imaging of m.3243A>G associated retinopathy
No full textRetro-mode illumination imaging can provide good visualization of chorio-retinal atrophy and of the retinal pigment epithelial alterations occurring in m.3243A > G associated retinopathy
Comparison of Tm-sensitized Ho:YAG and Ho:YLF crystals for a laser-pumped 2 mu m CW oscillator
No full textWe report on a comparison of YAG and YLF crystals for Tm,Ho based CW laser systems operating at 2 mu m. As pump source we have used both a Ti:Al2O3 laser and an array of diode lasers in order to quantitatively assess the relevance of the pump beam spatial features on the 2 mu m laser performance. The results are compared with the predictions of a computer simulation using a rate equation model
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