1,370 research outputs found
Anderson localization of a Tonks-Girardeau gas in potentials with controlled disorder
We theoretically demonstrate features of Anderson localization in the
Tonks-Girardeau gas confined in one-dimensional (1D) potentials with controlled
disorder. That is, we investigate the evolution of the single particle density
and correlations of a Tonks-Girardeau wave packet in such disordered
potentials. The wave packet is initially trapped, the trap is suddenly turned
off, and after some time the system evolves into a localized steady state due
to Anderson localization. The density tails of the steady state decay
exponentially, while the coherence in these tails increases. The latter
phenomenon corresponds to the same effect found in incoherent optical solitons
Sequential Desynchronization in Networks of Spiking Neurons with Partial Reset
The response of a neuron to synaptic input strongly depends on whether or not
it has just emitted a spike. We propose a neuron model that after spike
emission exhibits a partial response to residual input charges and study its
collective network dynamics analytically. We uncover a novel desynchronization
mechanism that causes a sequential desynchronization transition: In globally
coupled neurons an increase in the strength of the partial response induces a
sequence of bifurcations from states with large clusters of synchronously
firing neurons, through states with smaller clusters to completely asynchronous
spiking. We briefly discuss key consequences of this mechanism for more general
networks of biophysical neurons
Pattern Competition in the Photorefractive Semiconductors
We analytically study the photorefractive Gunn effect in n-GaAs subjected to
two external laser beams which form a moving interference pattern (MIP) in the
semiconductor. When the intensity of the spatially independent part of the MIP,
denoted by , is small, the system has a periodic domain train (PDT),
consistent with the results of linear stability analysis. When is large,
the space-charge field induced by the MIP will compete with the PDT and result
in complex dynamics, including driven chaos via quasiperiodic route
On the Photorefractive Gunn Effect
We present and numerically solve a model of the photorefractive Gunn effect.
We find that high field domains can be triggered by phase-locked interference
fringes, as it has been recently predicted on the basis of linear stability
considerations. Since the Gunn effect is intrinsically nonlinear, we find that
such considerations give at best order-of-magnitude estimations of the
parameters critical to the photorefractive Gunn effect. The response of the
system is much more complex including multiple wave shedding from the injecting
contact, wave suppression and chaos with spatial structure.Comment: Revtex, 8 pag., 4 fig. (jpg), submit to Physical Review
Visible Array Waveguide Gratings for Applications of Optical Neural Probes
In this paper we propose using Array Waveguide Gratings (AWGs), working in the visible range, in order to implement the technique of Wavelength-Division-(de)Multiplexing for multi-point stimulation of deep-brain neurons. We've developed a CMOS compatible fabrication process and fabricated two sets of AWGs, working in the red and blue wavelengths. Experimental data demonstrating the functionality of these AWGs is presented
An Analytical Approach to Neuronal Connectivity
This paper describes how realistic neuromorphic networks can have their
connectivity properties fully characterized in analytical fashion. By assuming
that all neurons have the same shape and are regularly distributed along the
two-dimensional orthogonal lattice with parameter , it is possible to
obtain the accurate number of connections and cycles of any length from the
autoconvolution function as well as from the respective spectral density
derived from the adjacency matrix. It is shown that neuronal shape plays an
important role in defining the spatial spread of network connections. In
addition, most such networks are characterized by the interesting phenomenon
where the connections are progressively shifted along the spatial domain where
the network is embedded. It is also shown that the number of cycles follows a
power law with their respective length. Morphological measurements for
characterization of the spatial distribution of connections, including the
adjacency matrix spectral density and the lacunarity of the connections, are
suggested. The potential of the proposed approach is illustrated with respect
to digital images of real neuronal cells.Comment: 4 pages, 6 figure
Induced Coherence and Stable Soliton Spiraling
We develop a theory of soliton spiraling in a bulk nonlinear medium and
reveal a new physical mechanism: periodic power exchange via induced coherence,
which can lead to stable spiraling and the formation of dynamical two-soliton
states. Our theory not only explains earlier observations, but provides a
number of predictions which are also verified experimentally. Finally, we show
theoretically and experimentally that soliton spiraling can be controled by the
degree of mutual initial coherence.Comment: 4 pages, 5 figure
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