Waveguides formed by incoherent dark solitons

We demonstrate experimentally optical guidance of coherent light beams, using incoherent light. Such guidance is made possible by generation of partially spatially incoherent self-trapped dark beams (dark incoherent solitons) in a noninstantaneous nonlinear medium. In the one-dimensional case, the incoherent solitons induce single and Y-junction planar waveguides, whereas in the two-dimensional case, they form circular waveguides. These experiments introduce the possibility of controlling high-power laser beams with low-power incoherent light sources such as LED's or lightbulbs.     

Linear combination of hybrid orbitals: Cyclobutane as test-case

Hybrid-based molecular orbitals are constructed for puckered cyclobutane, and used subsequently in a configurational-interaction process. The bent-bond structure, diagonal interaction and excited states of the molecule are discussed.     

Optimal paths in disordered complex networks

We study the optimal distance in networks, l(opt), defined as the length of the path minimizing the total weight, in the presence of disorder. Disorder is introduced by assigning random weights to the links or nodes. For strong disorder, where the maximal weight along the path dominates the sum, we find that l(opt) approximately N(1/3) in both Erdos-Rényi (ER) and Watts-Strogatz (WS) networks. For scale-free (SF) networks, with degree distribution P(k) approximately k(-lambda), we find that l(opt) scales as N((lambda-3)/(lambda-1)) for 3 or =4. Thus, for these networks, the small-world nature is destroyed. For 2相似文献   

Bright spatial solitons on a partially incoherent background

We present the first observation of incoherent antidark spatial solitons in noninstantaneous nonlinear media. This new class of soliton states involves bright solitons on a partially incoherent background of infinite extent. In the case where the nonlinearity is of the Kerr type, their existence is demonstrated analytically by means of an exact solution. Computer simulations and experiments indicate that these incoherent antidark solitons can propagate in a stable fashion provided that the spatial coherence of their background is reduced below the incoherent modulation instability threshold.     

Composite multihump vector solitons carrying topological charge

We propose composite solitons carrying topological charge: multicomponent two dimensional [ (2+1)D] vector (Manakov-like) solitons for which at least one component carries topological charge. These multimode solitons can have a single hump or exhibit a multihump structure. The "spin" carried by these multimode composite solitons suggests 3D soliton interactions in which the particlelike behavior includes spin, in addition to effective mass, linear, and angular momenta.     

Detection and sorting of neural spikes using wavelet packets

We propose a novel method for the detection and sorting of recorded neural spikes using wavelet packets. We employ the best basis via the Shannon's information cost function and local discriminant basis using mutual information. We demonstrate the efficiency of the method on data recorded in vitro from 2D neural networks. We show that our method is superior both in separation from noise and in identifying superimposed spikes.     

Cauchy's Flux Theorem in Light of Geometric Integration Theory

This work presents a formulation of Cauchy's flux theory of continuum mechanics in the framework of geometric integration theory as formulated by H. Whitney and extended recently by J. Harrison. Starting with convex polygons, one constructs a formal vector space of polyhedral chains. A Banach space of chains is obtained by a completion process of this vector space with respect to a norm. Then, integration operators, cochains, are defined as elements of the dual space to the space of chains. Thus, the approach links the analytical properties of cochains with the corresponding properties of the domains in an optimal way. The basic representation theorem shows that cochains may be represented by forms. The form representing a cochain is a geometric analog of a flux field in continuum mechanics.     

Generalized Stress Concentration Factors for Equilibrated Forces and Stresses

As a sequel to a recent work we consider the generalized stress concentration factor, a purely geometric property of a body that for the various loadings indicates the ratio between the maximum of the optimal stress and maximum of the loading fields. The optimal stress concentration factor pertains to a stress field that satisfies the principle of virtual work and for which the stress concentration factor is minimal. Unlike the previous work, we require that the external loading be equilibrated and that the stress field be a symmetric tensor field.     

On smoothly growing bodies and the eshelby tensor

A continuum mechanical theory of growing bodies is presented. It is assumed that the various parts of the body are identifiable. The growth of a body is manifested by mapping the identifiable elements of the growing body into a material manifold. Kinematics and stress theory are formulated on the basis of an infinite dimensional differentiable bundle structure for the configuration space. Stresses representing the forces associated with the growth of the body are analogous to the Eshelby tensor.

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Sommario Si propone una teoria meccanica dei corpi di massa crescente. Si postula che le varie parti del corpo siano identificabili. La crescita del corpo si manifesta mediante l'applicazione degli elementi identificabili del corpo in una varietà materiale. La cinematica e la teoria degli sforzi vengono formulati sulla base di un fibrato differenziabile a infinite dimensioni per lo spazio delle configurazioni. Gli sforzi associati alla crescita del corpo sono analoghi al tensore di Eshelby.