196,422 research outputs found
Geometry of D'Atri spaces of type k
No full textA Riemannian n-dimensional manifold M is a D'Atri space of type k (or k-D'Atri space), 1 ≤ k ≤ n - 1, if the geodesic symmetries preserve the k-th elementary symmetric functions of the eigenvalues of the shape operators of all small geodesic spheres in M. Symmetric spaces are k-D'Atri spaces for all possible k ≥ 1 and the property 1-D'Atri is the D'Atri condition in the usual sense. In this article we study some aspects of the geometry of k-D'Atri spaces, in particular those related to properties of Jacobi operators along geodesics. We show that k-D'Atri spaces for all k = 1,..., l satisfy that tr (Rvk), v a unit vector in TM, is invariant under the geodesic flow for all k = 1,..., l. Further, if M is k-D'Atri for all k = 1,..., n - 1, then the eigenvalues of Jacobi operators are constant functions along geodesics. In the case of spaces of Iwasawa type, we show that k-D'Atri spaces for all k = 1,..., n - 1 are exactly the symmetric spaces of noncompact type. Moreover, in the class of Damek-Ricci spaces, the symmetric spaces of rank one are characterized as those that are 3-D'Atri.Fil: Druetta, Maria Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Estudios de Matemática. Universidad Nacional de Córdoba. Centro de Investigación y Estudios de Matemática; Argentin
The Ledger curvature conditions and D'Atri geometry
No full textAbstractWe consider the third Ledger condition L3: (▽Xr)(X, X) = 0, which is a necessary condition for a Riemannian manifold M to be D'Atri. We show that, in dimension 5 or higher, there are Riemannian manifolds which satisfy L3 but are neither homogeneous nor D'Atri. We also show that, conversely, in dimension 3 L3 alone forces M to be D'Atri, and so in particular homogeneous
Tra sapere e sapori. I viaggiatori alla scoperta della Campania ottocentesca
No full textIl tentativo di ricostruire l’immagine della Campania ottocentesca – sospesa tra le bellezze paesaggistiche e artistiche e la cultura materiale, cibo in primis (due di quelle “felicità” di cui parla Piero Bevilacqua nel suo ultimo libro) – attraverso i viaggiatori appare come una scelta che vuole coniugare diversi piani metodologico-narrativi. Senza dimenticare che possiamo contare su una corposa produzionelegata tanto al romanzo quanto, in particolare, alla letteratura dei viaggiatori stranieri tra Otto e Novecento che, come è noto, avevano fatto di Napoli e dei suoi dintorni, una delle tappe del Gran Tour
Evaluating e-government projects on the basis of public policy effects
No full textThe evaluation of IT-based projects in Public Administration is mainly carried out on the basis of technical measures, like cost reductions, project timing, and degree of efficiency of IT spending. We show here, on the basis of a theoretically-grounded and process-based evaluation model, that what is truly important in e-government project evaluation is not only the generation of new IT assets (policy output), but also their proper use (policy outcome) and their final effects on policy takers (policy impact). Our case study shows how, a low-cost and small IT integration project can significantly leverage the legacy systems, enhancing the overall degree of IT conversion effectiveness (first stage), with expected positive effects on policy outcomes (second stage) and policy impacts (third stage). This theory-based approach may actually suggest new ways to evaluate e-government projects in order to maximize the value generated and, ultimately, to ensure a higher degree of actuation of public policy objective
'Industrial districts enterprises’ and ‘virtual enterprises’: proximity and distance, ICT- IS, and organizational learning
No full textInterdisciplinary Aspects of Information Systems Studies
No full textThe main goal of this book is to disseminate academic knowledge, both theoretical and pragmatic, in the information systems community. Recognizing the relevance of many different disciplines, the book takes an interdisciplinary approach to the subject of information systems, thus providing a comprehensive and current coverage of this important area
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