1,994 research outputs found
Potential implementation of Reservoir Computing models based on magnetic skyrmions
Reservoir Computing is a type of recursive neural network commonly used for
recognizing and predicting spatio-temporal events relying on a complex
hierarchy of nested feedback loops to generate a memory functionality. The
Reservoir Computing paradigm does not require any knowledge of the reservoir
topology or node weights for training purposes and can therefore utilize
naturally existing networks formed by a wide variety of physical processes.
Most efforts prior to this have focused on utilizing memristor techniques to
implement recursive neural networks. This paper examines the potential of
skyrmion fabrics formed in magnets with broken inversion symmetry that may
provide an attractive physical instantiation for Reservoir Computing.Comment: 11 pages, 3 figure
The Parameter-Less Self-Organizing Map algorithm
The Parameter-Less Self-Organizing Map (PLSOM) is a new neural network
algorithm based on the Self-Organizing Map (SOM). It eliminates the need for a
learning rate and annealing schemes for learning rate and neighbourhood size.
We discuss the relative performance of the PLSOM and the SOM and demonstrate
some tasks in which the SOM fails but the PLSOM performs satisfactory. Finally
we discuss some example applications of the PLSOM and present a proof of
ordering under certain limited conditions.Comment: 29 pages, 27 figures. Based on publication in IEEE Trans. on Neural
Network
Issues in the Scalability of Gate-level Morphogenetic Evolvable Hardware
Traditional approaches to evolvable hardware (EHW), in which the field programmable gate array (FPGA) configuration is directly encoded, have not scaled well with increasing circuit and FPGA complexity. To overcome this there have been moves towards encoding a growth process, known as morphogenesis. Using a morphogenetic approach, has shown success in scaling gate-level EHW for a signal routing problem, however, when faced with a evolving a one-bit full adder, unforseen difficulties were encountered. In this paper, we provide a measurement of EHW problem difficulty that takes into account the salient features of the problem, and when combined with a measure of feedback from the fitness function, we are able to estimate whether or not a given EHW problem is likely to be able to be solved successfully by our morphogenetic approach. Using these measurements we are also able to give an indication of the scalability of morphogenesis when applied to EHW
Induction of Topological Environment Maps from Sequences of Visited Places
In this paper we address the problem of topologically mapping environments which contain inherent perceptual aliasing caused by repeated environment structures. We propose an approach that does not use motion or odometric information but only a sequence of deterministic measurements observed by traversing an environment. Our algorithm implements a stochastic local search to build a small map which is consistent with local adjacency information extracted from a sequence of observations. Moreover, local adjacency information is incorporated to disambiguate places which are physically different but appear identical to the robots senses. Experiments show that the proposed method is capable of mapping environments with a high degree of perceptual aliasing, and that it infers a small map quickly
Interaction effects on almost flat surface bands in topological insulators
We consider ferromagnetic instabilities of two-dimensional helical Dirac
fermions hosted on the surface of three-dimensional topological insulators. We
investigate ways to increase the role of interactions by means of modifying the
bulk properties which in turn changes both the surface Dirac theory and the
screening of interactions. We discuss both the long-ranged part of the Coulomb
interactions controlled by the dimensionless coupling constant as well as the effects of local
interactions parametrized by the ratio of
a local interaction on the surface, , and the surface
bandwidth, . If large compared to 1, both mechanisms can
induce spontaneously surface ferromagnetism, thereby gapping the surface Dirac
metal and inducing an anomalous quantum Hall effect. We investigate two
mechanisms which can naturally lead to small Fermi velocities
and a corresponding small bandwidth
at the surface when the bulk band gap is reduced. The same mechanisms can,
however, also lead to an enhanced screening of surface interactions. While in
all considered cases the long-ranged part of the Coulomb interaction is
screened efficiently, , we discuss situations, where
becomes \emph{parametrically}\ large
compared to 1, thus inducing surface magnetism.Comment: 15 pages, 8 figures, published version with minor updat
Twists in Ferromagnetic Monolayers With Trigonal Prismatic Symmetry
Two-dimensional materials such as graphene or hexagonal boron nitride are
indispensable in industry. The recently discovered 2D ferromagnetic materials
also promise to be vital for applications. In this work, we develop a
phenomenological description of non-centrosymmetric 2D ferromagnets with
trigonal prismatic crystal structure. We chose to study this special symmetry
group since these materials do break inversion symmetry and therefore, in
principle, allow for chiral spin structures such as magnetic helices and
skyrmions. However, unlike all non-centrosymmetric magnets known so far, we
show that the symmetry of magnetic trigonal prismatic monolayers neither allow
for an internal relativistic Dzyaloshinskii-Moriya interaction (DMI) nor a
reactive spin-orbit torque. We demonstrate that the DMI only becomes important
at the boundaries, where it modifies the boundary conditions of the
magnetization and leads to a helical equilibrium state with a helical
wavevector that is inherently linked to the internal spin orientation.
Furthermore, we find that the helical wavevector can be electrically
manipulated via dissipative spin-torque mechanisms. Our results reveal that 2D
magnets offer a large potential for unexplored magnetic effects.Comment: 5 pages, 3 figure
- …