1,721,311 research outputs found
Il canto delle sirene. Scritti scelti 1969-1997
No full textIl libro propone una scelta significativa degli scritti critici di Biasin. L'introduzione scritta da A. Bertoni ricostruisce l'itinerario intellettuale dello studios
Phase lapses in scattering through multielectron quantum dots: Mean-field and few-particle regimes
Full text linkWe show that the observed evolution of the transmission phase through multielectron quantum dots with more than approximately ten electrons, which shows a universal (i.e., independent of N) as yet unexplained behavior, is consistent with an electrostatic model, where electron-electron interaction is described by a mean-field approach. Moreover, we perform exact calculations for an open one-dimensional quantum dot and show that carrier correlations may give rise to a nonuniversal (i.e., N-dependent) behavior of the transmission phase, ensuing from Fano resonances, which is consistent with experiments with a few (N < 10) carriers. Our results suggest that in the universal regime, the coherent transmission takes place through a single level, while in the few-particle regime, the correlated scattering state is determined by the number of bound particles
Entanglement and quantum computing with ballistic electrons
No full textWe first present a brief review of the basic requirements, proposals and prototype implementations for quantum computing devices. Then we introduce a specific universal set of quantum gates and describe a physical system, based on coupled quantum wires, that should be able to realize the proposed quantum transformations. Finally, the dynamics of entanglement-creation between two ballistic electrons is analysed for a model system
Scattering resonances in 1D coherent transport through a correlated quantum dot: An application of the few-particle quantum transmitting boundary method
No full textWe present a method for the calculation of thescattering states of a N + 1th-particle coherently interactingwith N correlated particles confined in a nanostructureand placed within an open domain. The method is based on ageneralization of the quantum transmitting boundary method[C. Lent and D. Kirkner, J. App. Phys. 67, 6353 (1990)].The antisymmetry conditions of the N + 1-identical particlescurrent-carrying state results from a proper choice ofthe boundary conditions. As an example which is relevant tocoherent electronics, we apply the method to compute the exacttransmission functions and phases of an electron crossinga 1D quantum dot with zero, one or two bound electrons
Random projections for assessing gene expression cluster stability
Full text linkClustering analysis of gene expression is characterized by the very high dimensionality and low cardinality of the data, and two important related topics are the validation and the estimate of the number of the obtained clusters.
In this paper we focus on the estimate of the stability of the clusters.
Our approach to this problem is based on random projections obeying the Johnson-Lindenstrauss lemma,by which gene expression data may be projected into randomly selected low dimensional subspaces, approximately preserving pairwise distances between examples.
We experiment with different types of random projections, comparing empirical and theoretical distortions induced by randomized embeddings between euclidean metric spaces, and we present cluster-stability measures that may be used to validate and to quantitatively assess the reliability of the clusters obtained by a large class of clustering algorithms.
Experimental results with high dimensional synthetic and DNA microarray data show the effectiveness of the proposed approach
Enterprise Risk Management e Corporate Financial Risk Management, Quaderno FINTEMA 2007, Milano, Egea
No full textNo abstract availabl
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