20,647 research outputs found
Quantum Properties of a Which-Way Detector
We explore quantum properties of a which-way detector using three versions of
an idealized two slit arrangements. Firstly we derive complementarity relations
for the detector; secondly we show how the "experiment" may be altered in such
a way that using single position measurement on the screen we can obtain
quantum erasure. Finally we show how to construct a superposition of "wave" and
"particle" components
Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows
We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN],
on the vanishing viscosity limit of circularly symmetric viscous flow in a disk
with rotating boundary, shown there to converge to the inviscid limit in
-norm as long as the prescribed angular velocity of the
boundary has bounded total variation. Here we establish convergence in stronger
and -Sobolev spaces, allow for more singular angular velocities
, and address the issue of analyzing the behavior of the boundary
layer. This includes an analysis of concentration of vorticity in the vanishing
viscosity limit. We also consider such flows on an annulus, whose two boundary
components rotate independently.
[LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J.,
Vanishing viscosity limit for incompressible flow inside a rotating circle,
preprint 2006
Virial coefficients from 2+1 dimensional QED effective actions at finite temperature and density
From spinor and scalar 2+1 dimensional QED effective actions at finite
temperature and density in a constant magnetic field background, we calculate
the corresponding virial coefficients for particles in the lowest Landau level.
These coefficients depend on a parameter theta related to the time-component of
the gauge field, which plays an essential role for large gauge invariance. The
variation of the parameter theta might lead to an interpolation between
fermionic and bosonic virial coefficients, although these coefficients are
singular for theta=pi/2.Comment: 10 Latex pages, no figures. Version to appear in MPL
Tuning in magnetic modes in Tb(Co_{x}Ni_{1-x})_{2}B_{2}C: from longitudinal spin-density waves to simple ferromagnetism
Neutron diffraction and thermodynamics techniques were used to probe the
evolution of the magnetic properties of Tb(Co_{x}Ni_{1-x})_{2}B_{2}C. A
succession of magnetic modes was observed as x is varied: the longitudinal
modulated k=(0.55,0,0) state at x=0 is transformed into a collinear
k=([nicefrac]\nicefrac{1}{2},0,[nicefrac]\nicefrac{1}{2})
antiferromagnetic state at x= 0.2, 0.4; then into a transverse c-axis modulated
k=(0,0,[nicefrac]\nicefrac{1}{3}) mode at x= 0.6, and finally
into a simple ferromagnetic structure at x= 0.8 and 1. Concomitantly, the
low-temperature orthorhombic distortion of the tetragonal unit cell at x=0 is
reduced smoothly such that for x >= 0.4 only a tetragonal unit cell is
manifested. Though predicted theoretically earlier, this is the first
observation of the k=(0,0,[nicefrac]\nicefrac{1}{3}) mode in
borocarbides; our findings of a succession of magnetic modes upon increasing x
also find support from a recently proposed theoretical model. The implication
of these findings and their interpretation on the magnetic structure of the
RM_{2}B_{2}C series are also discussed
Crescimento de bananeira "Grande Naine" sob diferentes lâminas de irrigação.
A banana é uma das frutas mais consumidas no mundo, e a sua produção se concentra em países de clima tropical. Apesar de ser um dos maiores produtores mundiais, o Brasil apresenta baixa produtividade média, quando comparado com outros países como Guatemala e Costa Rica (FAO, 2007). O baixo rendimento constatado nas regiões produtoras de banana evidencia a necessidade de ajustes tecnológicos e de manejo da cultura nas diversas áreas do conhecimento. Uma das tecnologias mais relevantes demandadas para esta cultura, diz respeito à irrigação, já que ela é muito sensível ao déficit hídrico e seu potencial produtivo depende de uma apreciável taxa de transpiração e boa uniformidade de distribuição de água durante o seu ciclo produtivo, não sendo fácil encontrar condições ecológicas naturais que satisfaçam todas as suas exigências (FIGUEIREDO, et al. 2006).pdf 180
Estimativa da divergência genética entre genótipos de feijão-caupi a partir de análises multivariadas.
Objetivou-se, neste trabalho, estimar a divergência genética entre genótipos de feijão-caupi por meio de técnicas multivariadas
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