The Experts below are selected from a list of 834942 Experts worldwide ranked by ideXlab platform
Xiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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unidirectional spectral Singularities
Physical Review Letters, 2014Co-Authors: Hamidreza Ramezani, Yuan Wang, Xiang ZhangAbstract:We propose a class of spectral Singularities emerging from the coincidence of two independent Singularities with highly directional responses. These spectral Singularities result from resonance trapping induced by the interplay between parity-time symmetry and Fano resonances. At these Singularities, while the system is reciprocal in terms of a finite transmission, a simultaneous infinite reflection from one side and zero reflection from the opposite side can be realized.
Ali Mostafazadeh - One of the best experts on this subject based on the ideXlab platform.
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spectral Singularities of complex scattering potentials and infinite reflection and transmission coefficients at real energies
Physical Review Letters, 2009Co-Authors: Ali MostafazadehAbstract:Spectral Singularities are spectral points that spoil the completeness of the eigenfunctions of certain non-Hermitian Hamiltonian operators. We identify spectral Singularities of complex scattering potentials with the real energies at which the reflection and transmission coefficients tend to infinity, i.e., they correspond to resonances having a zero width. We show that a waveguide modeled using such a potential operates like a resonator at the frequencies of spectral Singularities. As a concrete example, we explore the spectral Singularities of an imaginary PT-symmetric barrier potential and demonstrate the above resonance phenomenon for a certain electromagnetic waveguide.
Hamidreza Ramezani - One of the best experts on this subject based on the ideXlab platform.
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unidirectional spectral Singularities
Physical Review Letters, 2014Co-Authors: Hamidreza Ramezani, Yuan Wang, Xiang ZhangAbstract:We propose a class of spectral Singularities emerging from the coincidence of two independent Singularities with highly directional responses. These spectral Singularities result from resonance trapping induced by the interplay between parity-time symmetry and Fano resonances. At these Singularities, while the system is reciprocal in terms of a finite transmission, a simultaneous infinite reflection from one side and zero reflection from the opposite side can be realized.
Jean-françois Muzy - One of the best experts on this subject based on the ideXlab platform.
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Singularity spectrum of multifractal functions involving oscillating Singularities
Journal of Fourier Analysis and Applications, 1998Co-Authors: Alain Arneodo, Emmanuel Bacry, Stephane Jaffard, Jean-françois MuzyAbstract:We give general mathematical results concerning oscillating Singularities and we study examples of functions composed only of oscillating Singularities. These functions are defined by explicit coefficients on an orthonormal wavelet basis. We compute their Hölder regularity and oscillation at every point and we deduce their spectrum of oscillating Singularities.
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OSCILLATING Singularities IN LOCALLY SELF-SIMILAR FUNCTIONS
Physical Review Letters, 1995Co-Authors: Alain Arneodo, Emmanuel Bacry, Jean-françois MuzyAbstract:Singularities induced by oscillating behavior are analyzed using the wavelet transform. We define two local exponents which allow us to characterize both the singularity strength (Holder exponent) and the instantaneous frequency of the oscillations. Such oscillating Singularities are shown to appear generically in local self-similar functions which are invariant under a nonhyperbolic mapping. We illustrate our results on both isolated Singularities and nonisolated Singularities appearing in fractal signals generated by nonhyperbolic iterative function systems.
H U Bauer - One of the best experts on this subject based on the ideXlab platform.
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application of kohonen s self organizing feature map algorithm to cortical maps of orientation and direction preference
Proceedings of The Royal Society B: Biological Sciences, 1998Co-Authors: Nicholas V Swindale, H U BauerAbstract:Cortical maps of orientation preference in cats, ferrets and monkeys contain numerous half–rotation point Singularities. Experimental data have shown that direction preference also has a smooth representation in these maps, with preferences being for the most part orthogonal to the axis of preferred orientation. As a result, the orientation Singularities induce an extensive set of linear fractures in the direction map. These fractures run between and connect nearby point orientation Singularities. Their existence appears to pose a puzzle for theories that postulate that cortical maps maximize continuity of representation, because the fractures could be avoided if the orientation map contained full–rotation Singularities. Here we show that a dimension–reduction model of cortical map formation, which implements principles of continuity and completeness, produces an arrangement of linear direction fractures connecting point orientation Singularities which is similar to that observed experimentally. We analyse the behaviour of this model and suggest reasons why the model maps contain half–rotation rather than full–rotation orientation Singularities.
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Application of Kohonen's self–organizing feature map algorithm to cortical maps of orientation and direction preference
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1998Co-Authors: Nicholas V Swindale, H U BauerAbstract:Cortical maps of orientation preference in cats, ferrets and monkeys contain numerous half–rotation point Singularities. Experimental data have shown that direction preference also has a smooth representation in these maps, with preferences being for the most part orthogonal to the axis of preferred orientation. As a result, the orientation Singularities induce an extensive set of linear fractures in the direction map. These fractures run between and connect nearby point orientation Singularities. Their existence appears to pose a puzzle for theories that postulate that cortical maps maximize continuity of representation, because the fractures could be avoided if the orientation map contained full–rotation Singularities. Here we show that a dimension–reduction model of cortical map formation, which implements principles of continuity and completeness, produces an arrangement of linear direction fractures connecting point orientation Singularities which is similar to that observed experimentally. We analyse the behaviour of this model and suggest reasons why the model maps contain half–rotation rather than full–rotation orientation Singularities.
