7,388 research outputs found
Symmetry based determination of space-time functions in nonequilibrium growth processes
We study the space-time correlation and response functions in nonequilibrium
growth processes described by linear stochastic Langevin equations. Exploiting
exclusively the existence of space and time dependent symmetries of the
noiseless part of these equations, we derive expressions for the universal
scaling functions of two-time quantities which are found to agree with the
exact expressions obtained from the stochastic equations of motion. The
usefulness of the space-time functions is illustrated through the investigation
of two atomistic growth models, the Family model and the restricted Family
model, which are shown to belong to a unique universality class in 1+1 and in
2+1 space dimensions. This corrects earlier studies which claimed that in 2+1
dimensions the two models belong to different universality classes.Comment: 18 pages, three figures included, submitted to Phys. Rev.
NeXSPheRIO results on azimuthal anisotropy in Au-Au collisions at 200A GeV
In this work, we present the results obtained by the hydrodynamic code
NeXSPheRIO on anisotropic flows. In our calculation, we made use of
event-by-event fluctuating initial conditions, and chemical freeze-out was
explicitly implemented. We studied directed flow, elliptic flow and forth
harmonic coefficient for various hadrons at different centrality windows for
Au+Au collisions at 200 AGeV. The results are discussed and compared with
experimental data from RHIC.Comment: 6 pages and 6 figures, sqm2008 contributio
Desenvolvimento inicial de clones enxertados de murucizeiro em Igarapé-Açu, Pará.
O murucizeiro é uma espécie frutífera que vem demandando nos últimos anos informações sobre materiais que possam ser recomendados as diversas regiões de cultivo. Desta forma, o objetivo deste trabalho foi caracterizar clones de murucizeiro cultivados em Igarapé-Açu, Pará, quanto a aspectos vegetativos em seu primeiro ano de desenvolvimento. Os tratamentos consistiram de clones oriundos do BAG-murucizeiro da Embrapa Amazônia Oriental: Açu, Cristo, Guataçara, Igarapé-açu-1, Maracanã-1, Maracanã-2, Santarém-1, Santarém-2, São José, Tocantins-1 e Tocantins-2. Foram avaliados os seguintes caracteres morfológicos: altura de planta, diâmetro do caule, número de ramos e volume de copa. Observou-se que há variabilidade genética entre os clones de murucizeiro para os caracteres altura de planta, com destaque para os clones São José, Cristo e Maracanã 2, e também para o volume de copa, com destaque para o clone Maracanã 2. Apesar de não ter havido diferença significativa entre os clones para os caracteres diâmetro do caule e número de ramos, estudos fenológicos continuarão a ser realizados semestralmente, a fim de se identificar os clones que apresentam maior sustentação de copa
Ramond-Ramond Fields, Fractional Branes and Orbifold Differential K-Theory
We study D-branes and Ramond-Ramond fields on global orbifolds of Type II
string theory with vanishing H-flux using methods of equivariant K-theory and
K-homology. We illustrate how Bredon equivariant cohomology naturally realizes
stringy orbifold cohomology. We emphasize its role as the correct cohomological
tool which captures known features of the low-energy effective field theory,
and which provides new consistency conditions for fractional D-branes and
Ramond-Ramond fields on orbifolds. We use an equivariant Chern character from
equivariant K-theory to Bredon cohomology to define new Ramond-Ramond couplings
of D-branes which generalize previous examples. We propose a definition for
groups of differential characters associated to equivariant K-theory. We derive
a Dirac quantization rule for Ramond-Ramond fluxes, and study flat
Ramond-Ramond potentials on orbifolds.Comment: 46 pages; v2: typos correcte
Qualidade potencial dos cafés produzidos na "Região das Matas de Minas".
Em regiões de montanha, como característico na “Região das Matas de Minas”, a cafeicultura é uma atividade que depende de mão de obra, que além de cara está cada vez mais escassa, aumentando os custos de produção da atividade e com isso diminuindo a competitividade dos cafés no mercado mundial. Para que estes cafés produzidos na região se tornem mais competitivos, se faz necessário, o aumento da qualidade final dos mesmos. O café é um produto com aromas e sabores distintos que produz uma das bebidas mais difundidas no mundo, e tem o seu valor de mercado ajustado de acordo com a qualidade final da bebida, a qual pode ser influenciada por muitos fatores, tais como fatores ambientais e variedade da planta. Objetivou-se com este trabalho avaliar os efeitos da encosta da montanha, altitude e variedade de planta sobre os valores médios dos atributos de qualidade potencial dos cafés produzidos na “Região das Matas de Minas” (entre faixas de altitudes pertencentes aos intervalos: EA < 700, 700 < EA ? 825, 825 < EA <950 e EA ? 950 metros acima do nível do mar). Frutos de café (Coffea arabica L.) das variedades Catuaí Vermelho e Catuaí Amarelo foram colhidos manualmente em ponto de maturação cereja. A colheita foi realizada em fazendas localizadas em quatorze dos 63 municípios que compõem a “Região das Matas de Minas”, distribuídos numa pequena parte da região do Vale do Rio Doce e uma maior parte na região da Zona da Mata, num território de Mata Atlântica, a Leste do estado de Minas Gerais
On weak vs. strong universality in the two-dimensional random-bond Ising ferromagnet
We address the issue of universality in two-dimensional disordered Ising
systems, by considering long, finite-width strips of ferromagnetic Ising spins
with randomly distributed couplings. We calculate the free energy and spin-spin
correlation functions (from which averaged correlation lengths, ,
are computed) by transfer-matrix methods. An {\it ansatz} for the
size-dependence of logarithmic corrections to is proposed. Data for
both random-bond and site-diluted systems show that pure system behaviour (with
) is recovered if these corrections are incorporated, discarding the
weak--universality scenario.Comment: RevTeX code, 4 pages plus 2 Postscript figures; to appear in Physical
Review B Rapid Communication
Ising model on 3D random lattices: A Monte Carlo study
We report single-cluster Monte Carlo simulations of the Ising model on
three-dimensional Poissonian random lattices with up to 128,000 approx. 503
sites which are linked together according to the Voronoi/Delaunay prescription.
For each lattice size quenched averages are performed over 96 realizations. By
using reweighting techniques and finite-size scaling analyses we investigate
the critical properties of the model in the close vicinity of the phase
transition point. Our random lattice data provide strong evidence that, for the
available system sizes, the resulting effective critical exponents are
indistinguishable from recent high-precision estimates obtained in Monte Carlo
studies of the Ising model and \phi^4 field theory on three-dimensional regular
cubic lattices.Comment: 35 pages, LaTex, 8 tables, 8 postscript figure
Universality, frustration and conformal invariance in two-dimensional random Ising magnets
We consider long, finite-width strips of Ising spins with randomly
distributed couplings. Frustration is introduced by allowing both ferro- and
antiferromagnetic interactions. Free energy and spin-spin correlation functions
are calculated by transfer-matrix methods. Numerical derivatives and
finite-size scaling concepts allow estimates of the usual critical exponents
, and to be obtained, whenever a second-order
transition is present. Low-temperature ordering persists for suitably small
concentrations of frustrated bonds, with a transition governed by pure--Ising
exponents. Contrary to the unfrustrated case, subdominant terms do not fit a
simple, logarithmic-enhancement form. Our analysis also suggests a vertical
critical line at and below the Nishimori point. Approaching this point along
either the temperature axis or the Nishimori line, one finds non-diverging
specific heats. A percolation-like ratio is found upon analysis of
the uniform susceptibility at the Nishimori point. Our data are also consistent
with frustration inducing a breakdown of the relationship between
correlation-length amplitude and critical exponents, predicted by conformal
invariance for pure systems.Comment: RevTeX code for 10 pages, 9 eps figures, to appear in Physical Review
B (September 1999
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