28,209 research outputs found
Corrections to Finite Size Scaling in Percolation
A 1/L-expansion for percolation problems is proposed, where L is the lattice
finite length. The square lattice with 27 different sizes L = 18, 22 ... 1594
is considered. Certain spanning probabilities were determined by Monte Carlo
simulations, as continuous functions of the site occupation probability p. We
estimate the critical threshold pc by applying the quoted expansion to these
data. Also, the universal spanning probability at pc for an annulus with aspect
ratio r=1/2 is estimated as C = 0.876657(45)
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
Comportamento mandioca de mesa sob adubação, em área dependente de chuva, em Petrolina-PE.
Com objetivo de comparar comportamento das variedades de mandioca de mesa sob adubação, em área dependente de chuva, foi realizado o presente trabalho entre fevereiro de 2010 e novembro de 2011, nas comunidades Pereiros, Caiçara e Mudubim, pertencentes ao município de Petrolina/PE. A adubação constou de 2,0 t ha -1 de calcário dolomítico, em área total, e nos sulcos, 60 kg ha-1 de P22OO55, na forma de superfosfato simples, além da imersão das manivas cortadas numa solução de sulfato de zinco 2%. As variedades utilizadas foram Brasília e Gema de Ovo e o experimento foi realizado em delineamento inteiramente casualizado, com dois tratamentos e 4 repetições. Na ausência da adubação as variedades Brasília e Gema de Ovo não apresentaram diferenças significativas em produção de raízes e da planta inteira, porém na presença da calagem e fósforo a variedade Gema de Ovo supera a variedade Brasília em todos os aspectos de produtividade, seja da parte aérea, da raiz ou da planta inteira, apresentando respectivamente 18,7, 36,7 e 59,2 t.ha-1. A variedade Gema de Ovo destaca-se sobre as demais na produção de parte aérea nas comunidades dos Pereiros (19,85 t.ha-1) e Caiçara (13,87 t.ha-1), indicando ser uma variedade adequada, também para uso da parte aérea fenada na alimentação animal
Optimizing the ensemble for equilibration in broad-histogram Monte Carlo simulations
We present an adaptive algorithm which optimizes the statistical-mechanical
ensemble in a generalized broad-histogram Monte Carlo simulation to maximize
the system's rate of round trips in total energy. The scaling of the mean
round-trip time from the ground state to the maximum entropy state for this
local-update method is found to be O([N log N]^2) for both the ferromagnetic
and the fully frustrated 2D Ising model with N spins. Our new algorithm thereby
substantially outperforms flat-histogram methods such as the Wang-Landau
algorithm.Comment: 6 pages, 5 figure
Produção da parte aérea de variedades de mandioca em Petrolina-PE.
Com objetivo de avaliar a produção da parte aérea de variedades de mandioca, em área dependente de chuva, foi realizado o presente trabalho nas comunidades Pereiros, Caiçara e Mudubim, pertencentes ao município de Petrolina/PE no período de fevereiro de 2010 e setembro de 2011. O delineamento experimental usado foi blocos casualizados em esquema fatorial 4x2, compreendendo quatro variedades de mandioca (Engana Ladrão, Brasília, Gema de Ovo e Curvelinha) e dois tipos de adubação (com e sem), com quatro repetições. Os teores de fósforo aumentaram 23,9% na comunidade dos Pereiros, chegando a 87,2% na comunidade Mudubim, o que representa ganho real do elemento no solo com a adubação realizada. A variedade Gema de Ovo destacou-se sobre as demais na produção de parte aérea nas comunidades dos Pereiros (19,85 t.ha-1) e Caiçara (13,87 t.ha-1), indicando ser uma variedade com potencial para uso da parte aérea na alimentação animal
Turbulence and Chaos in Anti-de-Sitter Gravity
Due to the AdS/CFT correspondence the question of instability of
Anti-de-Sitter spacetimes sits in the intersection of mathematical and
numerical relativity, string theory, field theory and condensed matter physics.
In this essay we revisit that important question emphasizing the power of
spectral methods and highlighting the effectiveness of standard techniques for
studying nonlinear dynamical systems. In particular we display explicitly how
the problem can be modeled as a system on nonlinearly coupled harmonic
oscillators. We highlight some of the many open questions that stem from this
result and point out that a full understanding will necessarily required the
interdisciplinary cooperation of various communities.Comment: 6 pages, 12 figures. Essay awarded honorable mention in the Gravity
Research Foundation essay competition 201
Does Good Mutation Help You Live Longer?
We study the dynamics of an age-structured population in which the life
expectancy of an offspring may be mutated with respect to that of its parent.
When advantageous mutation is favored, the average fitness of the population
grows linearly with time , while in the opposite case the average fitness is
constant. For no mutational bias, the average fitness grows as t^{2/3}. The
average age of the population remains finite in all cases and paradoxically is
a decreasing function of the overall population fitness.Comment: 4 pages, 2 figures, RevTeX revised version, to appear in Phys. Rev.
Let
Speeding Up Computer Simulations: The Transition Observable Method
A method is presented which allows for a tremendous speed-up of computer
simulations of statistical systems by orders of magnitude. This speed-up is
achieved by means of a new observable, while the algorithm of the simulation
remains unchanged.Comment: 20 pages, 6 figures Submitted to Phys.Rev.E (August 1999) Replacement
due to some minor change
Projected single-spin flip dynamics in the Ising Model
We study transition matrices for projected dynamics in the
energy-magnetization space, magnetization space and energy space. Several
single spin flip dynamics are considered such as the Glauber and Metropolis
canonical ensemble dynamics and the Metropolis dynamics for three
multicanonical ensembles: the flat energy-magnetization histogram, the flat
energy histogram and the flat magnetization histogram. From the numerical
diagonalization of the matrices for the projected dynamics we obtain the
sub-dominant eigenvalue and the largest relaxation times for systems of varying
size. Although, the projected dynamics is an approximation to the full state
space dynamics comparison with some available results, obtained by other
authors, shows that projection in the magnetization space is a reasonably
accurate method to study the scaling of relaxation times with system size. The
transition matrices for arbitrary single-spin flip dynamics are obtained from a
single Monte-Carlo estimate of the infinite temperature transition-matrix, for
each system size, which makes the method an efficient tool to evaluate the
relative performance of any arbitrary local spin-flip dynamics. We also present
new results for appropriately defined average tunnelling times of magnetization
and compute their finite-size scaling exponents that we compare with results of
energy tunnelling exponents available for the flat energy histogram
multicanonical ensemble.Comment: 23 pages and 6 figure
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