10,326 research outputs found
Decoherence and the Loschmidt echo
Environment--induced decoherence causes entropy increase. It can be
quantified using, e.g., the purity . When the
Hamiltonian of a quantum system is perturbed, its sensitivity to such
perturbation can be measured by the Loschmidt echo . It is given by
the average squared overlap between the perturbed and unperturbed state. We
describe the relation between the temporal behavior of and . In this way we show that the decay of the Loschmidt echo can be analyzed
using tools developed in the study of decoherence. In particular, for systems
with a classically chaotic Hamiltonian the decay of and
has a regime where it is dominated by the classical Lyapunov exponent
Interpretation of runaway electron synchrotron and bremsstrahlung images
The crescent spot shape observed in DIII-D runaway electron synchrotron
radiation images is shown to result from the high degree of anisotropy in the
emitted radiation, the finite spectral range of the camera and the distribution
of runaways. The finite spectral camera range is found to be particularly
important, as the radiation from the high-field side can be stronger by a
factor than the radiation from the low-field side in DIII-D. By
combining a kinetic model of the runaway dynamics with a synthetic synchrotron
diagnostic we see that physical processes not described by the kinetic model
(such as radial transport) are likely to be limiting the energy of the
runaways. We show that a population of runaways with lower dominant energies
and larger pitch-angles than those predicted by the kinetic model provide a
better match to the synchrotron measurements. Using a new synthetic
bremsstrahlung diagnostic we also simulate the view of the Gamma Ray Imager
(GRI) diagnostic used at DIII-D to resolve the spatial distribution of
runaway-generated bremsstrahlung.Comment: 21 pages, 11 figure
Fractional Newton-Raphson Method Accelerated with Aitken's Method
The Newton-Raphson (N-R) method is characterized by the fact that generating
a divergent sequence can lead to the creation of a fractal, on the other hand
the order of the fractional derivatives seems to be closely related to the
fractal dimension, based on the above, a method was developed that makes use of
the N-R method and the fractional derivative of Riemann-Liouville (R-L) that
has been named as the Fractional Newton-Raphson (F N-R) method.
In the following work we present a way to obtain the convergence of the F N-R
method, which seems to be at least linearly convergent for the case where the
order of the derivative is different from one, a simplified way to
construct the fractional derivative and fractional integral operators of R-L is
presented, an introduction to the Aitken's method is made and it is explained
why it has the capacity to accelerate the convergence of iterative methods to
finally present the results that were obtained when implementing the Aitken's
method in F N-R method.Comment: Newton-Raphson Method, Fractional Calculus, Fractional Derivative of
Riemann-Liouville, Method of Aitken. arXiv admin note: substantial text
overlap with arXiv:1710.0763
Globally controlled universal quantum computation with arbitrary subsystem dimension
We introduce a scheme to perform universal quantum computation in quantum
cellular automata (QCA) fashion in arbitrary subsystem dimension (not
necessarily finite). The scheme is developed over a one spatial dimension
-element array, requiring only mirror symmetric logical encoding and global
pulses. A mechanism using ancillary degrees of freedom for subsystem specific
measurement is also presented.Comment: 7 pages, 1 figur
“Problemática de la Integración Universitaria en América del Sur”
Nuestro punto de partida es la actual tendencia que considera la región como una nueva categoría político-territorial donde, la verdadera integración entre países vecinos, sólo podrá lograrse contemplando las dimensiones económico-política y cultural-educativa. El surgimiento de este nuevo paradigma implica un reacomodamiento que genera la creación de nuevos mecanismos de regulación, imponiéndose, en los procesos de integración económica, una atención preferencial a los problemas de índole cultural ya que, los espacios de integración abarcan un amplio espectro que exceden las limitaciones impuestas por las fronteras del Estado-Nación y la macroeconomía. Este trabajo se realiza sobre la base de un análisis crítico de los documentos “Declaración Mundial sobre la Educación Superior en el Siglo XXI: Visión y Acción” y “Marco de Acción Prioritaria para el Cambio y el Desarrollo de la Educación Superior”, aprobados por la Conferencia Mundial sobre la Educación Superior (UNESCO,1998). A los fines de contextualizar el discurso, hacemos una primera aproximación al tema con planteos relacionados con la historia de la integración en América Latina. Nuestra intención es la de derivar la temática al campo regional del Noroeste Argentino teniendo en cuenta la historia institucional-educativa del área. A nivel metodológico comenzamos con una aclaración de los conceptos utilizados y, en segundo lugar, contrastamos el contenido de los documentos mencionados con la praxis integracionista de los últimos 20 años. América Latina, enfrenta el desafío de impulsar un desarrollo sostenible, que favorezca la inserción externa y promueva una creciente equidad interna. A la vez la inserción internacional plantea requisitos de innovación institucional, sustentabilidad ambiental y estrategia educacional. De una rápida revisión de los temas del debate contemporáneo podemos extraer varias líneas fundamentales que modifican los enfoques tradicionales de las problemáticas planteadas por las distintas áreas disciplinares; es a partir de aquí desde dónde, en última instancia, reflexionamos sobre las posibles alternativas de propuestas para la integración de las universidades de la región
Spike-based control monitoring and analysis with Address Event Representation
Neuromorphic engineering tries to mimic biological
information processing. Address-Event Representation (AER) is
a neuromorphic communication protocol for spiking neurons
between different chips. We present a new way to drive robotic
platforms using spiking neurons. We have simulated spiking
control models for DC motors, and developed a mobile robot
(Eddie) controlled only by spikes. We apply AER to the robot
control, monitoring and measuring the spike activity inside the
robot. The mobile robot is controlled by the AER-Robot tool,
and the AER information is sent to a PC using the
USBAERmini2 interface.Junta de Andalucía P06-TIC-01417Ministerio de Educación y Ciencia TEC2006-11730-C03-0
Hanging In, Stepping up and Stepping Out: Livelihood Aspirations and Strategies of the Poor Development in Practice
In recent years understanding of poverty and of ways in which people escape from or fall into poverty has become more holistic. This should improve the capabilities of policy analysts and others working to reduce poverty, but it also makes analysis more complex. This paper describes a simple schema which integrates multidimensional, multilevel and dynamic understandings of poverty, of poor people’s livelihoods, and of changing roles of agricultural systems. The paper suggests three broad types of strategy pursued by poor people: ‘hanging in’; ‘stepping up’; and ‘stepping out’. This simple schema explicitly recognises the dynamic aspirations of poor people; diversity among them; and livelihood diversification. It also brings together aspirations of poor people with wider sectoral, inter-sectoral and macro-economic questions about policies necessary for realisation of those aspirations
The non-self-adjointness of the radial momentum operator in n dimensions
The non self-adjointness of the radial momentum operator has been noted
before by several authors, but the various proofs are incorrect. We give a
rigorous proof that the -dimensional radial momentum operator is not self-
adjoint and has no self-adjoint extensions. The main idea of the proof is to
show that this operator is unitarily equivalent to the momentum operator on
which is not self-adjoint and has no self-adjoint
extensions.Comment: Some text and a reference adde
- …