3,010 research outputs found
A logic for n-dimensional hierarchical refinement
Hierarchical transition systems provide a popular mathematical structure to
represent state-based software applications in which different layers of
abstraction are represented by inter-related state machines. The decomposition
of high level states into inner sub-states, and of their transitions into inner
sub-transitions is common refinement procedure adopted in a number of
specification formalisms.
This paper introduces a hybrid modal logic for k-layered transition systems,
its first-order standard translation, a notion of bisimulation, and a modal
invariance result. Layered and hierarchical notions of refinement are also
discussed in this setting.Comment: In Proceedings Refine'15, arXiv:1606.0134
Canalizing Kauffman networks: non-ergodicity and its effect on their critical behavior
Boolean Networks have been used to study numerous phenomena, including gene
regulation, neural networks, social interactions, and biological evolution.
Here, we propose a general method for determining the critical behavior of
Boolean systems built from arbitrary ensembles of Boolean functions. In
particular, we solve the critical condition for systems of units operating
according to canalizing functions and present strong numerical evidence that
our approach correctly predicts the phase transition from order to chaos in
such systems.Comment: to be published in PR
Complexity-Entropy Causality Plane as a Complexity Measure for Two-dimensional Patterns
Complexity measures are essential to understand complex systems and there are
numerous definitions to analyze one-dimensional data. However, extensions of
these approaches to two or higher-dimensional data, such as images, are much
less common. Here, we reduce this gap by applying the ideas of the permutation
entropy combined with a relative entropic index. We build up a numerical
procedure that can be easily implemented to evaluate the complexity of two or
higher-dimensional patterns. We work out this method in different scenarios
where numerical experiments and empirical data were taken into account.
Specifically, we have applied the method to i) fractal landscapes generated
numerically where we compare our measures with the Hurst exponent; ii) liquid
crystal textures where nematic-isotropic-nematic phase transitions were
properly identified; iii) 12 characteristic textures of liquid crystals where
the different values show that the method can distinguish different phases; iv)
and Ising surfaces where our method identified the critical temperature and
also proved to be stable.Comment: Accepted for publication in PLoS On
Unplugging the Universe: the neglected electromagnetic consequence of decoupling
This letter concentrates on the non-equilibrium evolution of magnetic field
structures at the onset of recombination, when the charged particle current
densities decay as neutrals are formed.
We consider the effect that a decaying magnetic flux has on the acceleration
of particles via the transient induced electric field. Since the residual
charged-particle number density is small as a result of decoupling, we shall
consider the magnetic and electric fields essentially to be imposed, neglecting
the feedback from any minority accelerated population.
We find that the electromagnetic treatment of this phase transition can
produce energetic electrons scattered throughout the Universe. Such particles
could have a significant effect on cosmic evolution in several ways: (i) their
presence could delay the effective end of the recombination era; (ii) they
could give rise to plasma concentrations that could enhance early gravitational
collapse of matter by opposing cosmic expansion to a greater degree than
neutral matter could; (iii) they could continue to be accelerated, and become
the seed for reionisation at the later epoch .Comment: 4 pages, no figure
Is the equivalence for the response of static scalar sources in the Schwarzschild and Rindler spacetimes valid only in four dimensions?
It was shown recently that in four dimensions scalar sources with fixed
proper acceleration minimally coupled to a massless Klein-Gordon field lead to
the same responses when they are (i) uniformly accelerated in Minkowski
spacetime (in the inertial vacuum) and (ii) static in the Schwarzschild
spacetime (in the Unruh vacuum). Here we show that this equivalence is broken
if the spacetime dimension is more than four.Comment: 4 pages, 1 figur
Introdução à análise probabilÃstica simplificada da segurança estrutural
A análise da segurança de estruturas com vidas úteis diferentes das correntes, de estruturas existentes, de estruturas submetidas a acções invulgares, ou de estruturas reforçadas, é bastante complexa. A abordagem correcta deste problema não pode dispensar a utilização de modelos probabilÃsticos, que são desconhecidos da maioria dos engenheiros civis.
Neste trabalho é apresentada uma breve introdução à análise probabilÃstica simplificada da segurança, dando especial destaque à descrição dos modelos de acções e à análise de exemplos de aplicação
Scalar-tensor representation to brane with Gauss-Bonnet gravity
In this paper, we generalize the analysis of the brane via the
inclusion of a term proportional to the Gauss-Bonnet invariant. We consider an
action of the form , where is the trace of the
stress-energy tensor, is the Ricci scalar, and is a real parameter
that controls the contribution of the Gauss-Bonnet invariant . We introduce
the first-order formalism to obtain solutions for the source field of the brane
in the special case where and illustrate its procedure with
an application to the sine-Gordon model. We also investigate the general case
of the brane via the use of the scalar-tensor formalism, where we also
use the first-order formalism to obtain solutions. Finally, we investigate the
linear stability of the brane under tensor perturbations of the the modified
Einstein's field equations. Our results indicate that the Gauss-Bonnet term may
induce qualitatively different behaviors of the quantities on the brane,
provided that its contribution is large enough.Comment: 11 pages, 7 figure
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