258 research outputs found
Spin wave excitation patterns generated by spin torque oscillators
Spin torque nano oscillators (STNO) are nano-scale devices that can convert a direct current into short wave-length spin-wave excitations in a ferromagnetic layer. We show that arrays of STNO can be used to create directional spin-wave radiation similar to electromagnetic antennas. Combining STNO excitations with planar spin waves also creates interference patterns. We show that these interference patterns are static and have information on the wavelength and phase of the spin waves emitted from the STNO. We describe means of actively controlling spin-wave radiation patterns with the direct current flowing through STNO, which is useful in on-chip communication and information processing and could be a promising technique for studying short wave-length spin waves in different materials
Anisotropic spin-wave patterns generated by spin-torque nano-oscillators
Spin-wave excitations due to spin-momentum transfer in ferromagnetic thin films will enable new types of information processing and memory storage. Here, we show how arrays of spin-torque nano-oscillators (STNOs) can be used to create anisotropic spin-wave interference patterns, which can be used for information processing. We consider STNO arrays contacting a thin ferromagnetic film. Contacts to the film (including the STNOs themselves) can be used to detect the spin-waves and then, when coupled to a simple circuit, can create new excitation patterns. The propagating spin-wave patterns can be generated by pulsing transponders. Arrangements of transponders create resonant (reverberating) spin-wave activity-that may be the basis of polychronous wave computation of the arithmetic and Boolean functions as well as information storag
Asynchronous response of coupled pacemaker neurons
We study a network model of two conductance-based pacemaker neurons of
differing natural frequency, coupled with either mutual excitation or
inhibition, and receiving shared random inhibitory synaptic input. The networks
may phase-lock spike-to-spike for strong mutual coupling. But the shared input
can desynchronize the locked spike-pairs by selectively eliminating the lagging
spike or modulating its timing with respect to the leading spike depending on
their separation time window. Such loss of synchrony is also found in a large
network of sparsely coupled heterogeneous spiking neurons receiving shared
input.Comment: 11 pages, 4 figures. To appear in Phys. Rev. Let
Optical neuron using polarisation switching in a 1550nm-VCSEL
We report a new approach to mimic basic functionalities of a neuron using a 1550 nm Vertical Cavity Surface Emitting Laser (VCSEL) which is based on the polarisation switching (PS) that can be induced in these devices when subject to polarised optical injection. Positive and negative all-optical threshold operations are demonstrated experimentally using external optical injection into the two orthogonal polarizations of the fundamental transverse mode. The polarisation of the light emitted by the device is used to determine the state of the VCSEL-Neuron, active (orthogonal) or inactive (parallel). This approach forms a new way to reproduce optically the response of a neuron to an excitatory and an inhibitory stimulus. © 2010 Optical Society of America
Clustering and Synchronization of Oscillator Networks
Using a recently described technique for manipulating the clustering
coefficient of a network without changing its degree distribution, we examine
the effect of clustering on the synchronization of phase oscillators on
networks with Poisson and scale-free degree distributions. For both types of
network, increased clustering hinders global synchronization as the network
splits into dynamical clusters that oscillate at different frequencies.
Surprisingly, in scale-free networks, clustering promotes the synchronization
of the most connected nodes (hubs) even though it inhibits global
synchronization. As a result, scale-free networks show an additional, advanced
transition instead of a single synchronization threshold. This cluster-enhanced
synchronization of hubs may be relevant to the brain with its scale-free and
highly clustered structure.Comment: Submitted to Phys. Rev.
Small world effect in an epidemiological model
A model for the spread of an infection is analyzed for different population
structures. The interactions within the population are described by small world
networks, ranging from ordered lattices to random graphs. For the more ordered
systems, there is a fluctuating endemic state of low infection. At a finite
value of the disorder of the network, we find a transition to self-sustained
oscillations in the size of the infected subpopulation
Sensitivity analysis of circadian entrainment in the space of phase response curves
Sensitivity analysis is a classical and fundamental tool to evaluate the role
of a given parameter in a given system characteristic. Because the phase
response curve is a fundamental input--output characteristic of oscillators, we
developed a sensitivity analysis for oscillator models in the space of phase
response curves. The proposed tool can be applied to high-dimensional
oscillator models without facing the curse of dimensionality obstacle
associated with numerical exploration of the parameter space. Application of
this tool to a state-of-the-art model of circadian rhythms suggests that it can
be useful and instrumental to biological investigations.Comment: 22 pages, 8 figures. Correction of a mistake in Definition 2.1. arXiv
admin note: text overlap with arXiv:1206.414
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