9,521 research outputs found
Coherent States Expectation Values as Semiclassical Trajectories
We study the time evolution of the expectation value of the anharmonic
oscillator coordinate in a coherent state as a toy model for understanding the
semiclassical solutions in quantum field theory. By using the deformation
quantization techniques, we show that the coherent state expectation value can
be expanded in powers of such that the zeroth-order term is a classical
solution while the first-order correction is given as a phase-space Laplacian
acting on the classical solution. This is then compared to the effective action
solution for the one-dimensional \f^4 perturbative quantum field theory. We
find an agreement up to the order \l\hbar, where \l is the coupling
constant, while at the order \l^2 \hbar there is a disagreement. Hence the
coherent state expectation values define an alternative semiclassical dynamics
to that of the effective action. The coherent state semiclassical trajectories
are exactly computable and they can coincide with the effective action
trajectories in the case of two-dimensional integrable field theories.Comment: 20 pages, no figure
Polimorfismo de (GA)n intra e inter SSR em germoplasma mandioca.
O objetivo do trabalho foi comparar o polimorfismo de (GA)n Inter e Intra SSR na análise preliminar de acessos de germoplasma mantidos no Campo Experimental do Caldeirão, município de Iranduba
Exact Solution of the strong coupling t-V model with twisted boundary conditions
We present the solution of the one-dimensional t-V model with twisted
boundary conditions in the strong coupling limit, t<<V and show that this model
can be mapped onto the strong coupling Hubbard chain threaded by a fictitious
flux proportional to the total momentum of the charge carriers. The high energy
eigenstates are characterized by a factorization of degrees of freedom
associated with configurations of soliton and antisoliton domains and degrees
of freedom associated with the movement of ``holes'' through these domains. The
coexistence of solitons and antisolitons leads to a strange flux dependence of
the eigenvalues. We illustrate the use of this solution, deriving the full
frequency dependence of the optical conductivity at half-filling and zero
temperature.Comment: 11 pages, 1 figure; to be published in Physical Review
Genetic diversity among homonymy accessions maintained in the cassava regional Brazilian genebank.
In the Amazon region, the cassava cultivation has great social and economic importance because its production is source of food for traditional population and income for small farmers. The cassava farmer fields are results of the tradition and the preference of consumption and represent the genetic variability of many characters related to the mode of use and the quality of cassava root. The identification of genotypes to generate improved clones has been supported by germplasm conservation, evaluation and molecular characterization
Transverse momentum fluctuations and percolation of strings
The behaviour of the transverse momentum fluctuations with the centrality of
the collision shown by the Relativistic Heavy Ion Collider data is naturally
explained by the clustering of color sources. In this framework, elementary
color sources --strings-- overlap forming clusters, so the number of effective
sources is modified. These clusters decay into particles with mean transverse
momentum that depends on the number of elementary sources that conform each
cluster, and the area occupied by the cluster. The transverse momentum
fluctuations in this approach correspond to the fluctuations of the transverse
momentum of these clusters, and they behave essentially as the number of
effective sources.Comment: 16 pages, RevTex, 4 postscript figures. Enhanced version. New figure
Genetic diversity of cassava accessions from two regions of Amazon State, Brazil.
The study aimed to assess the genetic diversity of accessions collected in two regions from Amazon State, 120 from Lower Amazon River and 120 from Madeira River, using Inter Single Sequence Repeats (ISSR) markers
Inter-retrotransposon-amplified polymorphism markers for germplasm characterization in Manihot esculenta (Euphorbiaceae).
Manioc, Manihot esculenta, is economically important in many tropical and subtropical countries. The genetic variability of the species has not been fully explored, and new information may help expand its use. Molecular markers based on retrotransposons have good potential for analysis of genetic diversity given their abundance in the genome. Eight long terminal repeat retrotransposons were selected for the development of inter-retrotransposon-amplified polymorphism markers
System of forecasting agricultural crops using satellite observations of Earth
A preliminary description of a crop forecasting system is presented. Ground and satellite observation are the main sources of data collection
Hadronic sizes and observables in high-energy scattering
The functional dependence of the high-energy observables of total cross
section and slope parameter on the sizes of the colliding hadrons predicted by
the model of the stochastic vacuum and the corresponding relations used in the
geometric model of Povh and H\"ufner are confronted with the experimental data.
The existence of a universal term in the expression for the slope, due purely
to vacuum effects, independent of the energy and of the particular hadronic
system, is investigated. Accounting for the two independent correlation
functions of the QCD vacuum, we improve the simple and consistent description
given by the model of the stochastic vacuum to the high-energy pp and pbar-p
data, with a new determination of parameters of non-perturbative QCD. The
increase of the hadronic radii with the energy accounts for the energy
dependence of the observables.Comment: Latex, using Revtex.style . 2 ps figures. To be published in Physical
Review D , July 199
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