32,284 research outputs found
Susceptibility of a two-level atom near an isotropic photonic band edge: transparency and band edge profile reconstruction
We discuss the necessary conditions for a two-level system in the presence of
an isotropic band edge to be transparent to a probe laser field. The two-level
atom is transparent whenever it is coupled to a reservoir constituted of two
parts - a flat and a non-flat density of modes representing a PBG structure. A
proposal on the reconstruction of the band edge profile from the experimentally
measured susceptibility is also presented.Comment: 15 pages, 3 figure
Hermitian Dirac Hamiltonian in time dependent gravitational field
It is shown by a straightforward argument that the Hamiltonian generating the
time evolution of the Dirac wave function in relativistic quantum mechanics is
not hermitian with respect to the covariantly defined inner product whenever
the background metric is time dependent. An alternative, hermitian, Hamiltonian
is found and is shown to be directly related to the canonical field Hamiltonian
used in quantum field theory.Comment: 9 pages, final version, to appear in Class. Quant. Gra
Continuous and discontinuous absorbing-state phase transitions on Voronoi-Delaunay random lattices
We study absorbing-state phase transitions in two-dimensional
Voronoi-Delaunay (VD) random lattices with quenched coordination disorder.
Quenched randomness usually changes the criticality and destroys discontinuous
transitions in low-dimensional nonequilibrium systems. We performed extensive
simulations of the Ziff-Gulari-Barshad (ZGB) model, and verified that the VD
disorder does not change the nature of its discontinuous transition. Our
results corroborate recent findings of Barghatti and Vojta [Phys. Rev. Lett.
{\bf 113}, 120602 (2014)] stating the irrelevance of topological disorder in a
class of random lattices that includes VD and raise the interesting possibility
that disorder in nonequilibrium APT may, under certain conditions, be
irrelevant for the phase coexistence. We also verify that the VD disorder is
irrelevant for the critical behavior of models belonging to the directed
percolation and Manna universality classes.Comment: 7 pages, 6 figure
A utilização de Unidades Demonstrativas para a transferência de tecnologia.
A demonstração das tecnologias agrícolas é uma das formas de transferência adotadas pela Empresa Brasileira de Pesquisa Agropecuária ? Embrapa. Essa demonstração é feita para aproximar o agricultor dos benefícios gerados pela pesquisa. Nesse contexto, se insere o conceito de Unidade Demonstrativa (UD), mas o que vem a ser uma UD?bitstream/item/29508/1/adocao.pd
Temperature Measurement and Phonon Number Statistics of a Nanoelectromechanical Resonator
Measuring thermodynamic quantities can be easy or not, depending on the
system that is being studied. For a macroscopic object, measuring temperatures
can be as simple as measuring how much a column of mercury rises when in
contact with the object. At the small scale of quantum electromechanical
systems, such simple methods are not available and invariably detection
processes disturb the system state. Here we propose a method for measuring the
temperature on a suspended semiconductor membrane clamped at both ends. In this
method, the membrane is mediating a capacitive coupling between two
transmission line resonators (TLR). The first TLR has a strong dispersion, that
is, its decaying rate is larger than its drive, and its role is to pump in a
pulsed way the interaction between the membrane and the second TLR. By
averaging the pulsed measurements of the quadrature of the second TLR we show
how the temperature of the membrane can be determined. Moreover the statistical
description of the state of the membrane, which is directly accessed in this
approach is significantly improved by the addition of a Josephson Junction
coupled to the second TLR.Comment: 9 pages, 5 figures. To appear in New Journal of Physic
Informações técnicas sobre a colheita mecanizada do feijoeiro.
Do processo de produção do feijão a colheita é uma das etapas mais importantes. Quando mal processada pode acarretar em perdas de grãos e interferir de maneira decisiva na qualidade final do produto como, por exemplo, na perda no seu valor comercial. No sistema mecanizado todas as operações da colheita são feitas com máquina. Este sistema pode ser realizado por dois processos: direto e indireto. A vantagem de se realizar operações distintas está na qualidade final do produto, isso por que entre o corte e o enleiramento é necessário um intervalo para que as plantas sequem. Com isso, ocorre uma separação natural dos grãos com a terra, o que desfavorece o barreamento dos grãos no ato da trilha.bitstream/item/24032/1/itcm-pdf.pd
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