1,942 research outputs found
On Lie-algebraic solutions of the type IIB matrix model
A systematic search for Lie algebra solutions of the type IIB matrix model is
performed. Our survey is based on the classification of all Lie algebras for
dimensions up to five and of all nilpotent Lie algebras of dimension six. It is
shown that Lie-type solutions of the equations of motion of the type IIB matrix
model exist and they correspond to certain nilpotent and solvable Lie algebras.
Their representation in terms of Hermitian matrices is discussed in detail.
These algebras give rise to certain non-commutative spaces for which the
corresponding star-products are provided. Finally the issue of constructing
quantized compact nilmanifolds and solvmanifolds based on the above algebras is
addressed.Comment: 22 page
Bell inequalities for Continuous-Variable Measurements
Tests of local hidden variable theories using measurements with continuous
variable (CV) outcomes are developed, and a comparison of different methods is
presented. As examples, we focus on multipartite entangled GHZ and cluster
states. We suggest a physical process that produces the states proposed here,
and investigate experiments both with and without binning of the continuous
variable. In the former case, the Mermin-Klyshko inequalities can be used
directly. For unbinned outcomes, the moment-based CFRD inequalities are
extended to functional inequalities by considering arbitrary functions of the
measurements at each site. By optimising these functions, we obtain more robust
violations of local hidden variable theories than with either binning or
moments. Recent inequalities based on the algebra of quaternions and octonions
are compared with these methods. Since the prime advantage of CV experiments is
to provide a route to highly efficient detection via homodyne measurements, we
analyse the effect of noise and detection losses in both binned and unbinned
cases. The CV moment inequalities with an optimal function have greater
robustness to both loss and noise. This could permit a loophole-free test of
Bell inequalities.Comment: 17 pages, 6 figure
Resgate e conservação da flora no aproveitamento hidrelétrico Cana Brava, Goiás: relatório final.
Introdução e objetivos; Características gerais do reservatório; Estratégias de ação e métodos; Resultados; Anexo 1 "Check list" do Aproveitamento Hidrelétrico Cana Brava, Goiás, Brasil. Anexo 2 Lista de especies com germoplasma resgatado na área de influência do AHE Cana Brava.bitstream/item/130278/1/Rel-Final-Nov-2002.pd
Bell inequalities for continuous-variable correlations
We derive a new class of correlation Bell-type inequalities. The inequalities
are valid for any number of outcomes of two observables per each of n parties,
including continuous and unbounded observables. We show that there are no
first-moment correlation Bell inequalities for that scenario, but such
inequalities can be found if one considers at least second moments. The
derivation stems from a simple variance inequality by setting local commutators
to zero. We show that above a constant detector efficiency threshold, the
continuous variable Bell violation can survive even in the macroscopic limit of
large n. This method can be used to derive other well-known Bell inequalities,
shedding new light on the importance of non-commutativity for violations of
local realism.Comment: 4 pages, 1 figure. v2: New results on detector efficiencies and
macroscopic limit, new co-author, changed title and abstract, changed figure,
added journal reference and DO
Testing for Multipartite Quantum Nonlocality Using Functional Bell Inequalities
We show that arbitrary functions of continuous variables, e.g. position and
momentum, can be used to generate tests that distinguish quantum theory from
local hidden variable theories. By optimising these functions, we obtain more
robust violations of local causality than obtained previously. We analytically
calculate the optimal function and include the effect of nonideal detectors and
noise, revealing that optimized functional inequalities are resistant to
standard forms of decoherence. These inequalities could allow a loophole-free
Bell test with efficient homodyne detection
Mirando hacia el norte: clase, genero y etnicidad en los espacios de fruticultura del Nordeste de Brasil.
Este trabajo examina aspectos de la globalizació de los sistemas agroalimentarios, enfatizando los cambios socioeconómicos que tienen lugar en las nuevas regiones de fruticultura orientadas para los mercados del norte, según las dimensiones de clase, género y etnicidad. Las estrategias productivas usadas por los actores implicados para atender los requerimientos de calidad de las frutas, así como el contexto de las relaciones entre lo global y lo local, son analizadas, teniendo como base las investigaciones realizadas en el Nordeste brasileño
One-sided Device-Independent Quantum Key Distribution: Security, feasibility, and the connection with steering
We analyze the security and feasibility of a protocol for Quantum Key
Distribution (QKD), in a context where only one of the two parties trusts his
measurement apparatus. This scenario lies naturally between standard QKD, where
both parties trust their measurement apparatuses, and Device-Independent QKD
(DI-QKD), where neither does, and can be a natural assumption in some practical
situations. We show that the requirements for obtaining secure keys are much
easier to meet than for DI-QKD, which opens promising experimental
opportunities. We clarify the link between the security of this one-sided
DI-QKD scenario and the demonstration of quantum steering, in analogy to the
link between DI-QKD and the violation of Bell inequalities.Comment: v2 replaces the 3-page abstract posted as v1: our results are now
given with all necessary details. v3: published versio
Exact Solutions of the Klein-Gordon Equation in the Presence of a Dyon, Magnetic Flux and Scalar Potential in the Specetime of Gravitational Defects
In this paper we analyse the relativistic quantum motion of a charged spin-0
particle in the presence of a dyon, Aharonov-Bohm magnetic field and scalar
potential, in the spacetimes produced by an idealized cosmic string and global
monopole. In order to develop this analysis, we assume that the dyon and the
Aharonov-Bohm magnetic field are superposed to both gravitational defects. Two
distinct configurations for the scalar potential, , are considered:
the potential proportional to the inverse of the radial distance, i.e.,
, and the potential proportional to this distance, i.e.,
. For both cases the center of the potentials coincide with the
dyon's position. In the case of the cosmic string the Aharonov-Bohm magnetic
field is considered along the defect, and for the global monopole this magnetic
field pierces the defect. The energy spectra are computed for both cases and
explicitly shown their dependence on the electrostatic and scalar coupling
constants. Also we analyse scattering states of the Klein-Gordon equations, and
show how the phase shifts depend on the geometry of the spacetime and on the
coupling constants parameter.Comment: To be published in CQG. Minor comments adde
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