111 research outputs found
Classical and quantum behavior of dynamical systems defined by functions of solvable Hamiltonians
We discuss the classical and quantum mechanical evolution of systems
described by a Hamiltonian that is a function of a solvable one, both
classically and quantum mechanically. The case in which the solvable
Hamiltonian corresponds to the harmonic oscillator is emphasized. We show that,
in spite of the similarities at the classical level, the quantum evolution is
very different. In particular, this difference is important in constructing
coherent states, which is impossible in most cases. The class of Hamiltonians
we consider is interesting due to its pedagogical value and its applicability
to some open research problems in quantum optics and quantum gravity.Comment: Accepted for publication in American Journal of Physic
Probing Quantized Einstein-Rosen Waves with Massless Scalar Matter
The purpose of this paper is to discuss in detail the use of scalar matter
coupled to linearly polarized Einstein-Rosen waves as a probe to study quantum
gravity in the restricted setting provided by this symmetry reduction of
general relativity. We will obtain the relevant Hamiltonian and quantize it
with the techniques already used for the purely gravitational case. Finally we
will discuss the use of particle-like modes of the quantized fields to
operationally explore some of the features of quantum gravity within this
framework. Specifically we will study two-point functions, the Newton-Wigner
propagator, and radial wave functions for one-particle states.Comment: Accepted for publication in Physical Review
The Coupling of Shape Dynamics to Matter
Shape Dynamics (SD) is a theory dynamically equivalent to vacuum General
Relativity (GR), which has a different set of symmetries. It trades refoliation
invariance, present in GR, for local 3-dimensional conformal invariance. This
contribution to the Loops 11 conference addresses one of the more urgent
questions regarding the equivalence: is it possible to incorporate normal
matter in the new framework? The answer is yes, in certain regimes. We present
general criteria for coupling and apply it to a few examples.The outcome
presents bounds and conditions on scalar densities (such as the Higgs potential
and the cosmological constant) not present in GR.Comment: 4 pages. Contribution to Loops '11 conference in Madrid, to appear in
Journal of Physics: Conference Series (JPCS
The entangling side of the Unruh-Hawking effect
We show that the Unruh effect can create net quantum entanglement between
inertial and accelerated observers depending on the choice of the inertial
state. This striking result banishes the extended belief that the Unruh effect
can only destroy entanglement and furthermore provides a new and unexpected
source for finding experimental evidence of the Unruh and Hawking effects.Comment: 4 pages, 4 figures. Added Journal referenc
Time Uncertainty in Quantum Gravitational Systems
It is generally argued that the combined effect of Heisenberg principle and
general relativity leads to a minimum time uncertainty. Most of the analyses
supporting this conclusion are based on a perturbative approach to
quantization. We consider a simple family of gravitational models, including
the Einstein-Rosen waves, in which the (non-linearized) inclusion of gravity
changes the normalization of time translations by a monotonic energy-dependent
factor. In these circumstances, it is shown that a maximum time resolution
emerges non-perturbatively only if the total energy is bounded. Perturbatively,
however, there always exists a minimum uncertainty in the physical time.Comment: (4 pages, no figures) Accepted for publication in Physical Review
Pectin De-methylesterification and AGP Increase Promote Cell Wall Remodeling and Are Required During Somatic Embryogenesis of Quercus suber
Somatic embryogenesis is a reliable system for in vitro plant regeneration, with biotechnological applications in trees, but the regulating mechanisms are largely unknown. Changes in cell wall mechanics controlled by methylesterification of pectins, mediated by pectin methylesterases (PMEs) and pectin methyl esterase inhibitors (PMEIs) underlie many developmental processes. Arabinogalactan proteins (AGPs) are highly glycosylated proteins located at the surface of plasma membranes, in cell walls, and in extracellular secretions, with key roles in a range of different processes. In this study, we have investigated changes in two cell wall components, pectins and AGPs, during somatic embryogenesis in Quercus suber, a forest tree of high economic and ecologic value. At early embryogenesis stages, cells of proembryogenic masses showed high levels of esterified pectins and expression of QsPME and QsPMEI genes encoding a PME and a putative PMEI, respectively. At advanced stages, differentiating cells of heart, torpedo and cotyledonary embryos exhibited walls rich in de-esterified pectins, while QsPME gene expression and PME activity progressively increased. AGPs were detected in cell walls of proembryogenic masses and somatic embryos. QsLys-rich-AGP18, QsLys-rich-AGP17, and QsAGP16L1 gene expression increased with embryogenesis progression, as did the level of total AGPs, detected by dot blot with β-glucosyl Yariv reagent. Immuno dot blot, immunofluorescence assays and confocal analysis using monoclonal antibodies to high- (JIM7, LM20) and low- (JIM5, LM19) methylesterified pectins, and to certain AGP epitopes (LM6, LM2) showed changes in the amount and distribution pattern of esterified/de-esterified pectins and AGP epitopes, that were associated with proliferation and differentiation and correlated with expression of the PME and AGP genes analyzed. Pharmacological treatments with catechin, an inhibitor of PME activity, and Yariv reagent, which blocks AGPs, impaired the progression of embryogenesis, with pectin de-esterification and an increase in AGP levels being necessary for embryo development. Findings indicate a role for pectins and AGPs during somatic embryogenesis of cork oak, promoting the cell wall remodeling during the process. They also provide new insights into the regulating mechanisms of somatic embryogenesis in woody species, for which information is still scarce, opening up new possibilities to improve in vitro embryo production in tree breeding
Modulo móvil de educación de la energía solar
El Módulo Móvil de Educación consiste en una casilla rodante totalmente equipada con elementos de aprovechamiento de la Energía Solar.
La misma estará destinada a la educación, participando en exposiciones, charlas, conferencias, cursos, mesas redondas, sobre el tema difundiendo conocimientos teóricos y prácticos del aprovechamiento de la Energía Solar.
El móvil estará equipado con las luces, agua caliente heladera TV color, vídeo, computadora hornos, cocina, potabilizador de agua, radio, ventiladores, etcétera, todas funcionando a Energía Solar, como demostrando, en forma práctica y didáctica, todas la formas de aprovechamiento.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES
Modulo móvil de educación de la energía solar
El Módulo Móvil de Educación consiste en una casilla rodante totalmente equipada con elementos de aprovechamiento de la Energía Solar.
La misma estará destinada a la educación, participando en exposiciones, charlas, conferencias, cursos, mesas redondas, sobre el tema difundiendo conocimientos teóricos y prácticos del aprovechamiento de la Energía Solar.
El móvil estará equipado con las luces, agua caliente heladera TV color, vídeo, computadora hornos, cocina, potabilizador de agua, radio, ventiladores, etcétera, todas funcionando a Energía Solar, como demostrando, en forma práctica y didáctica, todas la formas de aprovechamiento.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES
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