12,638 research outputs found
String Theory and the Fuzzy Torus
We outline a brief description of non commutative geometry and present some
applications in string theory. We use the fuzzy torus as our guiding example.Comment: Invited review for IJMPA rev1: an imprecision corrected and a
reference adde
Almost automorphic delayed differential equations and Lasota-Wazewska model
Existence of almost automorphic solutions for abstract delayed differential
equations is established. Using ergodicity, exponential dichotomy and Bi-almost
automorphicity on the homogeneous part, sufficient conditions for the existence
and uniqueness of almost automorphic solutions are given.Comment: 16 page
Symmetry Breaking and Order in the Age of Quasicrystals
The discovery of quasicrystals has changed our view of some of the most basic
notions related to the condensed state of matter. Before the age of
quasicrystals, it was believed that crystals break the continuous translation
and rotation symmetries of the liquid-phase into a discrete lattice of
translations, and a finite group of rotations. Quasicrystals, on the other
hand, possess no such symmetries-there are no translations, nor, in general,
are there any rotations, leaving them invariant. Does this imply that no
symmetry is left, or that the meaning of symmetry should be revised? We review
this and other questions related to the liquid-to-crystal symmetry-breaking
transition using the notion of indistinguishability. We characterize the
order-parameter space, describe the different elementary excitations, phonons
and phasons, and discuss the nature of dislocations-keeping in mind that we are
now living in the age of quasicrystals.Comment: To appear in a special issue on quasicrystals of The Israel Journal
of Chemistry, in celebration of the 2011 Nobel Prize in Chemistr
Fuzzy Feedback Scheduling of Resource-Constrained Embedded Control Systems
The quality of control (QoC) of a resource-constrained embedded control
system may be jeopardized in dynamic environments with variable workload. This
gives rise to the increasing demand of co-design of control and scheduling. To
deal with uncertainties in resource availability, a fuzzy feedback scheduling
(FFS) scheme is proposed in this paper. Within the framework of feedback
scheduling, the sampling periods of control loops are dynamically adjusted
using the fuzzy control technique. The feedback scheduler provides QoC
guarantees in dynamic environments through maintaining the CPU utilization at a
desired level. The framework and design methodology of the proposed FFS scheme
are described in detail. A simplified mobile robot target tracking system is
investigated as a case study to demonstrate the effectiveness of the proposed
FFS scheme. The scheme is independent of task execution times, robust to
measurement noises, and easy to implement, while incurring only a small
overhead.Comment: To appear in International Journal of Innovative Computing,
Information and Contro
Chaos in the BMN matrix model
We study classical chaotic motions in the Berenstein-Maldacena-Nastase (BMN)
matrix model. For this purpose, it is convenient to focus upon a reduced system
composed of two-coupled anharmonic oscillators by supposing an ansatz. We
examine three ans\"atze: 1) two pulsating fuzzy spheres, 2) a single
Coulomb-type potential, and 3) integrable fuzzy spheres. For the first two
cases, we show the existence of chaos by computing Poincar\'e sections and a
Lyapunov spectrum. The third case leads to an integrable system. As a result,
the BMN matrix model is not integrable in the sense of Liouville, though there
may be some integrable subsectors.Comment: 23 pages, 15 figures, v2: further clarifications and references adde
Discrete and fuzzy dynamical genetic programming in the XCSF learning classifier system
A number of representation schemes have been presented for use within
learning classifier systems, ranging from binary encodings to neural networks.
This paper presents results from an investigation into using discrete and fuzzy
dynamical system representations within the XCSF learning classifier system. In
particular, asynchronous random Boolean networks are used to represent the
traditional condition-action production system rules in the discrete case and
asynchronous fuzzy logic networks in the continuous-valued case. It is shown
possible to use self-adaptive, open-ended evolution to design an ensemble of
such dynamical systems within XCSF to solve a number of well-known test
problems
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