12,031 research outputs found
Decoding of Repeated-Root Cyclic Codes up to New Bounds on Their Minimum Distance
The well-known approach of Bose, Ray-Chaudhuri and Hocquenghem and its
generalization by Hartmann and Tzeng are lower bounds on the minimum distance
of simple-root cyclic codes. We generalize these two bounds to the case of
repeated-root cyclic codes and present a syndrome-based burst error decoding
algorithm with guaranteed decoding radius based on an associated folded cyclic
code. Furthermore, we present a third technique for bounding the minimum
Hamming distance based on the embedding of a given repeated-root cyclic code
into a repeated-root cyclic product code. A second quadratic-time probabilistic
burst error decoding procedure based on the third bound is outlined. Index
Terms Bound on the minimum distance, burst error, efficient decoding, folded
code, repeated-root cyclic code, repeated-root cyclic product cod
Topological Model for Domain Walls in (Super-)Yang-Mills Theories
We derive a topological action that describes the confining phase of
(Super-)Yang-Mills theories with gauge group , similar to the work
recently carried out by Seiberg and collaborators. It encodes all the
Aharonov-Bohm phases of the possible non-local operators and phases generated
by the intersection of flux tubes. Within this topological framework we show
that the worldvolume theory of domain walls contains a Chern-Simons term at
level also seen in string theory constructions. The discussion can also
illuminate dynamical differences of domain walls in the supersymmetric and
non-supersymmetric framework. Two further analogies, to string theory and the
fractional quantum Hall effect might lead to additional possibilities to
investigate the dynamics
Subjective Performance Evaluations, Self-esteem, and Ego-threats in Principal-agent Relations
We conduct a laboratory experiment with agents working on and principals benefiting from a real effort task in which the agents’ effort/performance can only be evaluated subjectively. Principals give subjective performance feedback to agents and agents have an opportunity to sanction principals. We find that agents sanction whenever the feedback of principals is below their subjective self-evaluations even if the agents’ payoff is independent of the principals’ feedback. Based on our experimental analysis we propose a principal-agent model with subjective performance evaluations that accommodates this finding. We analyze the agents’ (optimal) behavior, optimal contracts, and social welfare in this environment.contracts; subjective performance evaluations; self-esteem; ego-threats
Finite Variation of Fractional Levy Processes
Various characterizations for fractional Levy process to be of finite
variation are obtained, one of which is in terms of the characteristic triplet
of the driving Levy process, while others are in terms of differentiability
properties of the sample paths. A zero-one law and a formula for the expected
total variation is also given.Comment: to appear in Journal of Theoretical Probabilit
Negative tension of scroll wave filaments and turbulence in three-dimensional excitable media and application in cardiac dynamics
Scroll waves are vortices that occur in three-dimensional excitable media. Scroll waves have been observed in a variety of systems including cardiac tissue, where they are associated with cardiac arrhythmias. The disorganization of scroll waves into chaotic behavior is thought to be the mechanism of ventricular fibrillation, whose lethality is widely known. One possible mechanism for this process of scroll wave instability is negative filament tension. It was discovered in 1987 in a simple two variables model of an excitable medium. Since that time, negative filament tension of scroll waves and the resulting complex, often turbulent dynamics was studied in many generic models of excitable media as well as in physiologically realistic models of cardiac tissue. In this article, we review the work in this area from the first simulations in FitzHugh-Nagumo type models to recent studies involving detailed ionic models of cardiac tissue. We discuss the relation of negative filament tension and tissue excitability and the effects of discreteness in the tissue on the filament tension. Finally, we consider the application of the negative tension mechanism to computational cardiology, where it may be regarded as a fundamental mechanism that explains differences in the onset of arrhythmias in thin and thick tissue
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