2,340 research outputs found
Monte Carlo simulation with fixed steplength for diffusion processes in nonhomogeneous media
Monte Carlo simulation is one of the most important tools in the study of diffusion processes. For constant diffusion coefficients, an appropriate Gaussian distribution of particle's steplengths can generate exact results, when compared with integration of the diffusion equation. It is important to notice that the same method is completely erroneous when applied to non-homogeneous diffusion coefficients. A simple alternative, jumping at fixed steplengths with appropriate transition probabilities, produces correct results. Here, a model for diffusion of calcium ions in the neuromuscular junction of the crayfish is used as a test to compare Monte Carlo simulation with fixed and Gaussian steplength.Fil: Ruiz Barlett, María Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; ArgentinaFil: Hoyuelos, Miguel Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; ArgentinaFil: Martin, Hector Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; Argentin
Discrete solitons and soliton-induced dislocations in partially-coherent photonic lattices
We investigate the interaction between a light beam and a two-dimensional
photonic lattice that is photo-induced in a photorefractive crystal using
partially coherent light. We demonstrate that this interaction process is
associated with a host of new phenomena including lattice dislocation, lattice
deformation, and creation of structures akin to optical polarons. In addition,
two-dimensional discrete solitons are realized in such partially coherent
photonic lattices.Comment: 12 pages, 4 figures (revised). accepted by Phys. Rev. Let
Martin Hector collection of papers, 1938-1954.
Interview with granddaughter Mary Halland about Hector and his early business ventures. Includes obituaries of Martin Hector, son Fred Hector, newspaper clipping of Fargo home referred to as the Henry Hector home, photocopy of Hammerfest, Norway church record of Hector's family (in Norwegian) and a typed English translation of the record
Connecting nth order generalised quantum Rabi models: Emergence of nonlinear spin-boson coupling via spin rotations
We establish an approximate equivalence between a generalised quantum Rabi
model and its nth order counterparts where spin-boson interactions are
nonlinear as they comprise a simultaneous exchange of bosonic excitations.
Although there exists no unitary transformation between these models, we
demonstrate their equivalence to a good approximation in a wide range of
parameters. This shows that nonlinear spin-boson couplings, i.e. nth order
quantum Rabi models, are accessible to quantum systems with only linear
coupling between boson and spin modes by simply adding spin rotations and after
an appropriate transformation. Furthermore, our result prompts novel
approximate analytical solutions to the dynamics of the quantum Rabi model in
the ultrastrong coupling regime improving previous approaches.Comment: 9 pages, 3 figures plus Supplemental Informatio
Effective equations for isotropic quantum cosmology including matter
Effective equations often provide powerful tools to develop a systematic
understanding of detailed properties of a quantum system. This is especially
helpful in quantum cosmology where several conceptual and technical
difficulties associated with the full quantum equations can be avoided in this
way. Here, effective equations for Wheeler-DeWitt and loop quantizations of
spatially flat, isotropic cosmological models sourced by a massive or
interacting scalar are derived and studied. The resulting systems are
remarkably different from that given for a free, massless scalar. This has
implications for the coherence of evolving states and the realization of a
bounce in loop quantum cosmology.Comment: 42 page
Turning the information-sharing dial: efficient inference from different data sources
A fundamental aspect of statistics is the integration of data from different
sources. Classically, Fisher and others were focused on how to integrate
homogeneous (or only mildly heterogeneous) sets of data. More recently, as data
is becoming more accessible, the question of if data sets from different
sources should be integrated is becoming more relevant. The current literature
treats this as a question with only two answers: integrate or don't. Here we
take a different approach, motivated by information-sharing principles coming
from the shrinkage estimation literature. In particular, we deviate from the
do/don't perspective and propose a dial parameter that controls the extent to
which two data sources are integrated. How far this dial parameter should be
turned is shown to depend, for example, on the informativeness of the different
data sources as measured by Fisher information. In the context of generalized
linear models, this more nuanced data integration framework leads to relatively
simple parameter estimates and valid tests/confidence intervals. Moreover, we
demonstrate both theoretically and empirically that setting the dial parameter
according to our recommendation leads to more efficient estimation compared to
other binary data integration schemes.Comment: 35 pages, 8 figures, 4 table
- …