3,012 research outputs found
The quantum-to-classical transition: contraction of associative products
The quantum-to-classical transition is considered from the point of view of
contractions of associative algebras. Various methods and ideas to deal with
contractions of associative algebras are discussed that account for a large
family of examples. As an instance of them, the commutative algebra of
functions in phase space, corresponding to classical physical observables, is
obtained as a contraction of the Moyal star-product which characterizes the
quantum case. Contractions of associative algebras associated to Lie algebras
are discussed, in particular the Weyl-Heisenberg and groups are
considered.Comment: 21 pages, 1 figur
Groupoids and the tomographic picture of quantum mechanics
The existing relation between the tomographic description of quantum states
and the convolution algebra of certain discrete groupoids represented on
Hilbert spaces will be discussed. The realizations of groupoid algebras based
on qudit, photon-number (Fock) states and symplectic tomography quantizers and
dequantizers will be constructed. Conditions for identifying the convolution
product of groupoid functions and the star--product arising from a
quantization--dequantization scheme will be given. A tomographic approach to
construct quasi--distributions out of suitable immersions of groupoids into
Hilbert spaces will be formulated and, finally, intertwining kernels for such
generalized symplectic tomograms will be evaluated explicitly
A tomographic setting for quasi-distribution functions
The method of constructing the tomographic probability distributions
describing quantum states in parallel with density operators is presented.
Known examples of Husimi-Kano quasi-distribution and photon number tomography
are reconsidered in the new setting. New tomographic schemes based on coherent
states and nonlinear coherent states of deformed oscillators, including
q-oscillators, are suggested. The associated identity decompositions providing
Gram-Schmidt operators are explicitly given, and contact with the Agarwal-Wolf
-operator ordering theory is made.Comment: A slightly enlarged version in which contact with the Agarwal-Wolf
-operator ordering theory is mad
Realization of associative products in terms of Moyal and tomographic symbols
The quantizer-dequantizer method allows to construct associative products on
any measure space. Here we consider an inverse problem: given an associative
product is it possible to realize it within the quantizer-dequantizer
framework? The answer is positive in finite dimensions and we give a few
examples in infinite dimensions.Comment: 13 pages. To appear on Physica Script
Optical supercavitation in soft-matter
We investigate theoretically, numerically and experimentally nonlinear
optical waves in an absorbing out-of-equilibrium colloidal material at the
gelification transition. At sufficiently high optical intensity, absorption is
frustrated and light propagates into the medium. The process is mediated by the
formation of a matter-shock wave due to optically induced thermodiffusion, and
largely resembles the mechanism of hydrodynamical supercavitation, as it is
accompanied by a dynamic phase-transition region between the beam and the
absorbing material.Comment: 4 pages, 5 figures, revised version: corrected typos and reference
39-K Bose-Einstein condensate with tunable interactions
We produce a Bose-Einstein condensate of 39-K atoms. Condensation of this
species with naturally small and negative scattering length is achieved by a
combination of sympathetic cooling with 87-Rb and direct evaporation,
exploiting the magnetic tuning of both inter- and intra-species interactions at
Feshbach resonances. We explore tunability of the self-interactions by studying
the expansion and the stability of the condensate. We find that a 39-K
condensate is interesting for future experiments requiring a weakly interacting
Bose gas.Comment: 5 page
Towards a knowledge-based system to assist the Brazilian data-collecting system operation
A study is reported which was carried out to show how a knowledge-based approach would lead to a flexible tool to assist the operation task in a satellite-based environmental data collection system. Some characteristics of a hypothesized system comprised of a satellite and a network of Interrogable Data Collecting Platforms (IDCPs) are pointed out. The Knowledge-Based Planning Assistant System (KBPAS) and some aspects about how knowledge is organized in the IDCP's domain are briefly described
Surrogate-based Real-time Curbside Management for Ride-hailing and Delivery Operations
The present work investigates surrogate model-based optimization for
real-time curbside traffic management operations. An optimization problem is
formulated to minimize the congestion on roadway segments caused by vehicles
stopping on the segment (e.g., ride-hailing or delivery operations) and
implemented in a model predictive control framework. A hybrid simulation
approach where main traffic flows interact with individually modeled stopping
vehicles is adopted. Due to its non-linearity, the optimization problem is
coupled with a meta-heuristic. However, because simulations are time expensive
and hence unsuitable for real-time control, a trained surrogate model that
takes the decision variables as inputs and approximates the objective function
is employed to replace the simulation within the meta-heuristic algorithm.
Several modeling techniques (i.e., linear regression, polynomial regression,
neural network, radial basis network, regression tree ensemble, and Gaussian
process regression) are compared based on their accuracy in reproducing
solutions to the problem and computational tractability for real-time control
under different configurations of simulation parameters. It is found that
Gaussian process regression is the most suited for use as a surrogate model for
the given problem. Finally, a realistic application with multiple ride-hailing
vehicle operations is presented. The proposed approach for controlling the stop
positions of vehicles is able to achieve an improvement of 20.65% over the
uncontrolled case. The example shows the potential of the proposed approach in
reducing the negative impacts of stopping vehicles and favorable computational
properties
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