73 research outputs found
Master Operators Govern Multifractality in Percolation
Using renormalization group methods we study multifractality in percolation
at the instance of noisy random resistor networks. We introduce the concept of
master operators. The multifractal moments of the current distribution (which
are proportional to the noise cumulants of the
resistance between two sites x and located on the same cluster) are
related to such master operators. The scaling behavior of the multifractal
moments is governed exclusively by the master operators, even though a myriad
of servant operators is involved in the renormalization procedure. We calculate
the family of multifractal exponents for the scaling behavior of the
noise cumulants, ,
where is the correlation length exponent for percolation, to two-loop
order.Comment: 6 page
Diluted Networks of Nonlinear Resistors and Fractal Dimensions of Percolation Clusters
We study random networks of nonlinear resistors, which obey a generalized
Ohm's law, . Our renormalized field theory, which thrives on an
interpretation of the involved Feynman Diagrams as being resistor networks
themselves, is presented in detail. By considering distinct values of the
nonlinearity r, we calculate several fractal dimensions characterizing
percolation clusters. For the dimension associated with the red bonds we show
that at least to order {\sl O} (\epsilon^4),
with being the correlation length exponent, and , where d
denotes the spatial dimension. This result agrees with a rigorous one by
Coniglio. Our result for the chemical distance, d_{\scriptsize min} = 2 -
\epsilon /6 - [ 937/588 + 45/49 (\ln 2 -9/10 \ln 3)] (\epsilon /6)^2 + {\sl O}
(\epsilon^3) verifies a previous calculation by one of us. For the backbone
dimension we find D_B = 2 + \epsilon /21 - 172 \epsilon^2 /9261 + 2 (- 74639 +
22680 \zeta (3))\epsilon^3 /4084101 + {\sl O} (\epsilon^4), where , in agreement to second order in with a two-loop
calculation by Harris and Lubensky.Comment: 29 pages, 7 figure
Effects of surfaces on resistor percolation
We study the effects of surfaces on resistor percolation at the instance of a
semi-infinite geometry. Particularly we are interested in the average
resistance between two connected ports located on the surface. Based on general
grounds as symmetries and relevance we introduce a field theoretic Hamiltonian
for semi-infinite random resistor networks. We show that the surface
contributes to the average resistance only in terms of corrections to scaling.
These corrections are governed by surface resistance exponents. We carry out
renormalization group improved perturbation calculations for the special and
the ordinary transition. We calculate the surface resistance exponents
\phi_{\mathcal S \mathnormal} and \phi_{\mathcal S \mathnormal}^\infty for
the special and the ordinary transition, respectively, to one-loop order.Comment: 19 pages, 3 figure
Componentes dos frutos de cultivares de coqueiro-anão (Cocos nucifera L. Var. Nana).
Estabelece as percentagens dos componentes de frutos de coqueiro anao, nos pontos de colheita para agua de coco, seis meses e sete meses, e para albumen solido, doze meses.bitstream/item/91445/1/CPATC-PESQ.-AND.-64-98.pd
Intermediate temperature dynamics of one-dimensional Heisenberg antiferromagnets
We present a general theory for the intermediate temperature (T) properties
of Heisenberg antiferromagnets of spin-S ions on p-leg ladders, valid for 2Sp
even or odd. Following an earlier proposal for 2Sp even (Damle and Sachdev,
cond-mat/9711014), we argue that an integrable, classical, continuum model of a
fixed-length, 3-vector applies over an intermediate temperature range; this
range becomes very wide for moderate and large values of 2Sp. The coupling
constants of the effective model are known exactly in terms of the energy gap
above the ground state (for 2Sp even) or a crossover scale (for 2Sp odd).
Analytic and numeric results for dynamic and transport properties are obtained,
including some exact results for the spin-wave damping. Numerous quantitative
predictions for neutron scattering and NMR experiments are made. A general
discussion on the nature of T>0 transport in integrable systems is also
presented: an exact solution of a toy model proves that diffusion can exist in
integrable systems, provided proper care is taken in approaching the
thermodynamic limit.Comment: 38 pages, including 12 figure
Nicho trófico de Abelha-branca (Frieseomelitta doederelini) na região do Submédio do Vale do São Francisco.
Com este trabalho, objetivou-se identificar as espécies vegetais que formam o nicho trófico da abelha-branca (Frieseomelitta doederleini), uma abelha-sem-ferrão potencialmente importante para a meliponicultura na região do Submédio do Vale do São Francisco
Interfacial adsorption phenomena of the three-dimensional three-state Potts model
We study the interfacial adsorption phenomena of the three-state
ferromagnetic Potts model on the simple cubic lattice by the Monte Carlo
method. Finite-size scaling analyses of the net-adsorption yield the evidence
of the phase transition being of first-order and .Comment: 14 page
Nonequilibrium relaxation of the two-dimensional Ising model: Series-expansion and Monte Carlo studies
We study the critical relaxation of the two-dimensional Ising model from a
fully ordered configuration by series expansion in time t and by Monte Carlo
simulation. Both the magnetization (m) and energy series are obtained up to
12-th order. An accurate estimate from series analysis for the dynamical
critical exponent z is difficult but compatible with 2.2. We also use Monte
Carlo simulation to determine an effective exponent, z_eff(t) = - {1/8} d ln t
/d ln m, directly from a ratio of three-spin correlation to m. Extrapolation to
t = infinity leads to an estimate z = 2.169 +/- 0.003.Comment: 9 pages including 2 figure
New Dynamic Monte Carlo Renormalization Group Method
The dynamical critical exponent of the two-dimensional spin-flip Ising model
is evaluated by a Monte Carlo renormalization group method involving a
transformation in time. The results agree very well with a finite-size scaling
analysis performed on the same data. The value of is
obtained, which is consistent with most recent estimates
Níveis séricos de selênio de cabras da raça Saanen criadas em ambiente tropical.
Resumo: Objetivou-se com este estudo analisar os níveis de selênio no sangue de cabras leiteiras criadas em ambiente tropical. O estudo foi realizado na Fazenda Experimental pertencente à Universidade Estadual Vale do Acaraú- UVA, com 12 cabras da raça Sannen, não prenhes e clinicamente saudáveis. As fêmeas foram criadas em regime semiextensivo, pela manhã ficavam em pasto nativo e à tarde retornavam para o galpão, permanecendo em baias individuais e recebiam concentrado adicionado de selênio orgânico na sua dieta. Antes e após a suplementação com selênio orgânico foi realizada a coleta de sangue para determinação dos níveis de selênio sérico. Observaram-se maiores níveis séricos de selênio após sua adição no concentrado. A utilização do selênio orgânico na dieta das cabras aumentou as concentrações sanguíneas desse micromineral na época seca do ano na região semiárida. [Serum selenium levels of Saanen goats in a tropical environment]. Abstract: The study aimed to analyze the levels of selenium in the blood of dairy goats in tropical environment. The study was conducted at the Experimental Farm from Universidade Estadual Vale do Acaraú - UVA with 12 goats Sannen race, not pregnant and clinically healthy. Females were raised in semi extensive diet, in the morning they were in native pasture and in the afternoon they returned to the barn, staying in individual stalls and they received concentrate added by organic selenium in their diet. Before and after supplementation with organic selenium, blood collection was performed to determine the serum levels of selenium. Higher serum levels of selenium could be observed after its addition in the concentrate. The use of organic selenium in the diet of goats increased blood concentrations of this trace mineral in the dry season in the semiarid region
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