33,635 research outputs found
Transmission coefficient and two-fold degenerate discrete spectrum of spin-1 bosons in a double-step potential
The scattering of spin-1 bosons in a nonminimal vector double-step potential
is described in terms of eigenstates of the helicity operator and it is shown
that the transmission coefficient is insensitive to the choice of the
polarization of the incident beam. Poles of the transmission amplitude reveal
the existence of a two-fold degenerate spectrum. The results are interpreted in
terms of solutions of two coupled effective Schr\"{o}dinger equations for a
finite square well with additional -functions situated at the borders.Comment: arXiv admin note: substantial text overlap with arXiv:1203.119
On Galois-Division Multiple Access Systems: Figures of Merit and Performance Evaluation
A new approach to multiple access based on finite field transforms is
investigated. These schemes, termed Galois-Division Multiple Access (GDMA),
offer compact bandwidth requirements. A new digital transform, the Finite Field
Hartley Transform (FFHT) requires to deal with fields of characteristic p, p
\neq 2. A binary-to-p-ary (p \neq 2) mapping based on the opportunistic
secondary channel is introduced. This allows the use of GDMA in conjunction
with available digital systems. The performance of GDMA is also evaluated.Comment: 6 pages, 4 figures. In: XIX Simposio Brasileiro de Telecomunicacoes,
2001, Fortaleza, CE, Brazi
Optimization of hierarchical structures of information flow
The efficiency of a large hierarchical organisation is simulated on
Barabasi-Albert networks, when each needed link leads to a loss of information.
The optimum is found at a finite network size, corresponding to about five
hierarchical layers, provided a cost for building the network is included in
our optimization.Comment: Draft of 6 pages including all figure
Spatial patterns and biodiversity in off-lattice simulations of a cyclic three-species Lotka-Volterra model
Stochastic simulations of cyclic three-species spatial predator-prey models
are usually performed in square lattices with nearest neighbor interactions
starting from random initial conditions. In this Letter we describe the results
of off-lattice Lotka-Volterra stochastic simulations, showing that the
emergence of spiral patterns does occur for sufficiently high values of the
(conserved) total density of individuals. We also investigate the dynamics in
our simulations, finding an empirical relation characterizing the dependence of
the characteristic peak frequency and amplitude on the total density. Finally,
we study the impact of the total density on the extinction probability, showing
how a low population density may jeopardize biodiversity.Comment: 5 pages, 7 figures; new version, with new title and figure
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