1,721,430 research outputs found
Irreducible symplectic varieties from moduli spaces of sheaves on K3 and Abelian surfaces
Full text linkWe show that the moduli spaces of sheaves on a projective K3 surface are irreducible symplectic varieties, and that the same holds for the fibers of the Albanese map of moduli spaces of sheaves on an Abelian surface
La ricerca nel dottorato. Architettura e Costruzione
No full textAldo Rossi afferma che porre la questione del tema
e del carattere come questione decisiva pone una
scelta che sta prima del progetto architettonico e nel
far questo pone in primo piano, necessariamente, l’aspetto
tipologico dell’architettura.
É la costruzione che permette il passaggio dal tipo
alla forma, la quale sarà portatrice del senso generale
del tema dell’edificio, del suo carattere.
Se viene applicato un sistema costruttivo diverso ad
una stessa tipologia, ne corrisponderà un diverso carattere
e una diversa forma.
Ne sono un esempio le basiliche romaniche e le cattedrali
gotiche che, pur avendo in comune la stessa
tipologia, presentano un carattere completamente
diverso: austero le prime, luminoso le seconde
Collective excitability, synchronization, and array-enhanced coherence resonance in a population of lasers with a saturable absorber
No full textIn this article we present a numerical study of the collective dynamics in a population of coupled semiconductor lasers with a saturable absorber, operating in the excitable regime under the action of additive noise. We demonstrate that temporal and intensity synchronization takes place in a broad region of the parameter space and for various array sizes. The synchronization is robust and occurs even for a set of nonidentical coupled lasers. The cooperative nature of the system results in a self-organization process which enhances the coherence of the single element of the population too and can have broad impact for detection purposes, for building all-optical simulators of neural networks and in the field of photonics-based computation
Array-enhanced synchronization and coherence resonance in coupled excitable semiconductor lasers
No full textWe present a numerical study of the nonlinear dynamics of a population of coupled semiconductor lasers with saturable absorber operating in the excitable regime [1] and described by a set of coupled Yamada models [2]. In particular we have investigated the self-organized synchronization process taking place spontaneously among the lasers, showing significant correlations between the spike-like pulses emitted by different lasers. Our findings demonstrate that synchronization in time and also in intensity occurs in a large region of the parameter space and for different population sizes and furthermore it is robust with respect to random distribution of the lasers' pump parameter which is linked to the excitability threshold
Disorder-induced localization of excitability in an array of coupled lasers
No full textWe report on the localization of excitability induced by disorder in an array of coupled semiconductor lasers with a saturable absorber. Through numerical simulations we show that the exponential localization of excitable waves occurs if a certain critical amount of randomness is present in the coupling coefficients among the lasers. The results presented in this Rapid Communication demonstrate that disorder can induce localization in lattices of excitable nonlinear oscillators, and can be of interest in the study of photonics-based random networks, neuromorphic systems, and, by analogy, in biology, in particular, in the investigation of the collective dynamics of neuronal cell populations
Collective dynamics of evanescently coupled excitable lasers with saturable absorber
No full textWe present a numerical study of the collective dynamics in a population of coupled excitable lasers with saturable absorber. At variance with previous studies where real-valued (lossy) coupling was considered, we focus here on the purely imaginary coupling (evanescent wave coupling). We show that evanescently coupled excitable lasers exhibit synchronization like the lossy coupled ones. Furthermore, we show that out-of-diagonal disorder-induced localization of excitability takes place for imaginary coupling too, but it can be frustrated by nonvanishing linewidth enhancement factor
Deformation of the O'Grady moduli spaces
No full textIn this paper we study moduli spaces of sheaves on an abelian or projective K3 surface. If S is a K3, v = 2w is a Mukai vector on S, where w is primitive and w(2) = 2, and H is a v-generic polarization on S, then the moduli space M-v of H-semistable sheaves on S whose Mukai vector is v admits a symplectic resolution (M) over tilde (v). A particular case is the 10-dimensional O'Grady example (M) over tilde (10) of an irreducible symplectic manifold. We show that (M) over tilde (v) is an irreducible symplectic manifold which is deformation equivalent to (M) over tilde (10) and that H-2 (M-v, Z) is Hodge isometric to the sublattice v(perpendicular to) of the Mukai lattice of S. Similar results are shown when S is an abelian surface
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Riprogettazione della filiera logistica nel settore degli impianti di sollevamento e trasporto persone per edilizia. Un modello concettuale ed uno studio di caso.
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