101 research outputs found
Coherent Schwinger Interaction from Darboux Transformation
The exactly solvable scalar-tensor potential of the four-component Dirac
equation has been obtained by the Darboux transformation method. The
constructed potential has been interpreted in terms of nucleon-nucleon and
Schwinger interactions of neutral particles with lattice sites during their
channeling Hamiltonians of a Schwinger type is obtained by means of the Darboux
transformation chain. The analitic structure of the Lyapunov function of
periodic continuation for each of the Hamiltonians of the family is considered.Comment: 12 pages, Latex, six figures; six sections, one figure adde
Automatic Classification of Roof Shapes for Multicopter Emergency Landing Site Selection
Geographic information systems (GIS) now provide accurate maps of terrain,
roads, waterways, and building footprints and heights. Aircraft, particularly
small unmanned aircraft systems, can exploit additional information such as
building roof structure to improve navigation accuracy and safety particularly
in urban regions. This paper proposes a method to automatically label building
roof shape types. Satellite imagery and LIDAR data from Witten, Germany are fed
to convolutional neural networks (CNN) to extract salient feature vectors.
Supervised training sets are automatically generated from pre-labeled buildings
contained in the OpenStreetMap database. Multiple CNN architectures are trained
and tested, with the best performing networks providing a condensed feature set
for support vector machine and decision tree classifiers. Satellite and LIDAR
data fusion is shown to provide greater classification accuracy than through
use of either data type individually
Parity nonconservation effects in the photodesintegration of polarized deuterons
P-odd correlations in the deuteron photodesintegration are considered. The
-meson exchange is not operative in the case of unpolarized deuterons. For
polarized deuterons a P-odd correlation due to the -meson exchange is
about . Short-distance P-odd contributions exceed essentially
than the contribution of the -meson exchange.Comment: 12 pages, Latex, 3 figure
Nucleon Polarizabilities from Deuteron Compton Scattering within a Green's-Function Hybrid Approach
We examine elastic Compton scattering from the deuteron for photon energies
ranging from zero to 100 MeV, using state-of-the-art deuteron wave functions
and NN-potentials. Nucleon-nucleon rescattering between emission and absorption
of the two photons is treated by Green's functions in order to ensure gauge
invariance and the correct Thomson limit. With this Green's-function hybrid
approach, we fulfill the low-energy theorem of deuteron Compton scattering and
there is no significant dependence on the deuteron wave function used.
Concerning the nucleon structure, we use Chiral Effective Field Theory with
explicit \Delta(1232) degrees of freedom within the Small Scale Expansion up to
leading-one-loop order. Agreement with available data is good at all energies.
Our 2-parameter fit to all elastic data leads to values for the
static isoscalar dipole polarizabilities which are in excellent agreement with
the isoscalar Baldin sum rule. Taking this value as additional input, we find
\alpha_E^s= (11.3+-0.7(stat)+-0.6(Baldin)) x 10^{-4} fm^3 and \beta_M^s =
(3.2-+0.7(stat)+-0.6(Baldin)) x 10^{-4} fm^3 and conclude by comparison to the
proton numbers that neutron and proton polarizabilities are essentially the
same.Comment: 47 pages LaTeX2e with 20 figures in 59 .eps files, using graphicx.
Minor modifications; extended discussion of theoretical uncertainties of
polarisabilities extraction. Version accepted for publication in EPJ
Infinite Nuclear Matter on the Light Front: Nucleon-Nucleon Correlations
A relativistic light front formulation of nuclear dynamics is developed and
applied to treating infinite nuclear matter in a method which includes the
correlations of pairs of nucleons: this is light front Brueckner theory. We
start with a hadronic meson-baryon Lagrangian that is consistent with chiral
symmetry. This is used to obtain a light front version of a one-boson-exchange
nucleon-nucleon potential (OBEP). The accuracy of our description of the
nucleon-nucleon (NN) data is good, and similar to that of other relativistic
OBEP models. We derive, within the light front formalism, the Hartree-Fock and
Brueckner Hartree-Fock equations. Applying our light front OBEP, the nuclear
matter saturation properties are reasonably well reproduced. We obtain a value
of the compressibility, 180 MeV, that is smaller than that of alternative
relativistic approaches to nuclear matter in which the compressibility usually
comes out too large. Because the derivation starts from a meson-baryon
Lagrangian, we are able to show that replacing the meson degrees of freedom by
a NN interaction is a consistent approximation, and the formalism allows one to
calculate corrections to this approximation in a well-organized manner. The
simplicity of the vacuum in our light front approach is an important feature in
allowing the derivations to proceed. The mesonic Fock space components of the
nuclear wave function are obtained also, and aspects of the meson and nucleon
plus-momentum distribution functions are computed. We find that there are about
0.05 excess pions per nucleon.Comment: 39 pages, RevTex, two figure
Nucleon-Nucleon Interaction: A Typical/Concise Review
Nearly a recent century of work is divided to Nucleon-Nucleon (NN)
interaction issue. We review some overall perspectives of NN interaction with a
brief discussion about deuteron, general structure and symmetries of NN
Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN
interaction models, as frameworks to build NN potentials, are reviewed
concisely. We try to include and study almost all well-known potentials in a
similar way, discuss more on various commonly used plain forms for two-nucleon
interaction with an emphasis on the phenomenological and meson-exchange
potentials as well as the constituent-quark potentials and new ones based on
chiral effective field theory and working in coordinate-space mostly. The
potentials are constructed in a way that fit NN scattering data, phase shifts,
and are also compared in this way usually. An extra goal of this study is to
start comparing various potentials forms in a unified manner. So, we also
comment on the advantages and disadvantages of the models and potentials partly
with reference to some relevant works and probable future studies.Comment: 85 pages, 5 figures, than the previous v3 edition, minor changes, and
typos fixe
Quantum-Mechanical Histories and the Uncertainty Principle: I.Information-Theoretic Inequalities
This paper is generally concerned with understanding how the uncertainty
principle arises in formulations of quantum mechanics, such as the decoherent
histories approach, whose central goal is the assignment of probabilities to
histories. We first consider histories characterized by position or momentum
projections at two moments of time. Both exact and approximate (Gaussian)
projections are studied. Shannon information is used as a measure of the
uncertainty expressed in the probabilities for these histories. We derive a
number of inequalities in which the uncertainty principle is expressed as a
lower bound on the information of phase space distributions derived from the
probabilities for two-time histories. We go on to consider histories
characterized by position samplings at moments of time. We derive a lower
bound on the information of the joint probability for position samplings.
Similar bounds are derived for histories characterized by samplings of other
variables. All lower bounds on the information of histories have the general
form , where is a volume element of
history space, which we define, and is the volume of that space probed by
the projections. We thus obtain a concise and general form of the uncertainty
principle referring directly to the histories description of the system, and
making no reference to notions of phase space.Comment: 40 pages (revised uncorrupted version), Imperial College Preprint IC
92-93/2
Quantum majorization and a complete set of entropic conditions for quantum thermodynamics
What does it mean for one quantum process to be more disordered than another? Interestingly, this apparently abstract question arises naturally in a wide range of areas such as information theory, thermodynamics, quantum reference frames, and the resource theory of asymmetry. Here we use a quantum-mechanical generalization of majorization to develop a framework for answering this question, in terms of single-shot entropies, or equivalently, in terms of semi-definite programs. We also investigate some of the applications of this framework, and remarkably find that, in the context of quantum thermodynamics it provides the first complete set of necessary and sufficient conditions for arbitrary quantum state transformations under thermodynamic processes, which rigorously accounts for quantum-mechanical properties, such as coherence. Our framework of generalized thermal processes extends thermal operations, and is based on natural physical principles, namely, energy conservation, the existence of equilibrium states, and the requirement that quantum coherence be accounted for thermodynamically
- …