233 research outputs found
SU(3) phase states and finite Fourier transform
We describe the construction of SU(3) phase operators using Fourier-like
transform on a hexagonal lattice. The advantages and disadvantages of this
approach are contrasted with other results, in particular with the more
traditional approach based on polar decomposition of operators.Comment: to appear in Physica Script
A simple derivation of Kepler's laws without solving differential equations
Proceeding like Newton with a discrete time approach of motion and a
geometrical representation of velocity and acceleration, we obtain Kepler's
laws without solving differential equations. The difficult part of Newton's
work, when it calls for non trivial properties of ellipses, is avoided by the
introduction of polar coordinates. Then a simple reconsideration of Newton's
figure naturally leads to en explicit expression of the velocity and to the
equation of the trajectory. This derivation, which can be fully apprehended by
beginners at university (or even before) can be considered as a first
application of mechanical concepts to a physical problem of great historical
and pedagogical interest
Transition from discrete to continuous time of arrival distribution for a quantum particle
We show that the Kijowski distribution for time of arrivals in the entire
real line is the limiting distribution of the time of arrival distribution in a
confining box as its length increases to infinity. The dynamics of the confined
time of arrival eigenfunctions is also numerically investigated and
demonstrated that the eigenfunctions evolve to have point supports at the
arrival point at their respective eigenvalues in the limit of arbitrarilly
large confining lengths, giving insight into the ideal physical content of the
Kijowsky distribution.Comment: Accepted for publication in Phys. Rev.
Peculiarities of the Weyl - Wigner - Moyal formalism for scalar charged particles
A description of scalar charged particles, based on the Feshbach-Villars
formalism, is proposed. Particles are described by an object that is a Wigner
function in usual coordinates and momenta and a density matrix in the charge
variable. It is possible to introduce the usual Wigner function for a large
class of dynamical variables. Such an approach explicitly contains a measuring
device frame. From our point of view it corresponds to the Copenhagen
interpretation of quantum mechanics. It is shown how physical properties of
such particles depend on the definition of the coordinate operator. The
evolution equation for the Wigner function of a single-charge state in the
classical limit coincides with the Liouville equation. Localization
peculiarities manifest themselves in specific constraints on possible initial
conditions.Comment: 16 pages, 2 figure
Dynamics of dissipative gravitational collapse
The Misner and Sharp approach to the study of gravitational collapse is
extended to the dissipative case in, both, the streaming out and the diffusion
approximations. The role of different terms in the dynamical equation are
analyzed in detail. The dynamical equation is then coupled to a causal
transport equation in the context of Israel--Stewart theory. The decreasing of
the inertial mass density of the fluid, by a factor which depends on its
internal thermodynamics state, is reobtained, at any time scale. In accordance
with the equivalence principle, the same decreasing factor is obtained for the
gravitational force term. Prospective applications of this result to some
astrophysical scenarios are discussed.Comment: Some misprints in eqs.(38) and (39) correcte
Point prevalence of surgical checklist use in Europe: relationship with hospital mortality
Background The prevalence of use of the World Health Organization surgical checklist is unknown. The clinical effectiveness of this intervention in improving postoperative outcomes is debated. Methods We undertook a retrospective analysis of data describing surgical checklist use from a 7 day cohort study of surgical outcomes in 28 European nations (European Surgical Outcomes Study, EuSOS). The analysis included hospitals recruiting >10 patients and excluding outlier hospitals above the 95th centile for mortality. Multivariate logistic regression and three-level hierarchical generalized mixed models were constructed to explore the relationship between surgical checklist use and hospital mortality. Findings are presented as crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs). Results A total of 45 591 patients from 426 hospitals were included in the analysis. A surgical checklist was used in 67.5% patients, with marked variation across countries (0-99.6% of patients). Surgical checklist exposure was associated with lower crude hospital mortality (OR 0.84, CI 0.75-0.94; P=0.002). This effect remained after adjustment for baseline risk factors in a multivariate model (adjusted OR 0.81, CI 0.70-0.94; P<0.005) and strengthened after adjusting for variations within countries and hospitals in a three-level generalized mixed model (adjusted OR 0.71, CI 0.58-0.85; P<0.001). Conclusions The use of surgical checklists varies across European nations. Reported use of a checklist was associated with lower mortality. This observation may represent a protective effect of the surgical checklist itself, or alternatively, may be an indirect indicator of the quality of perioperative care. Clinical trial registration The European Surgical Outcomes Study is registered with ClinicalTrials.gov, number NCT0120360
Duality between a deterministic cellular automaton and a bosonic quantum field theory in 1+1 dimensions
Methods developed in a previous paper are employed to define an exact
correspondence between the states of a deterministic cellular automaton in 1+1
dimensions and those of a bosonic quantum field theory. The result may be used
to argue that quantum field theories may be much closer related to
deterministic automata than what is usually thought possible. Version 2 had a
minor typo corrected and notation was made more consistent.Comment: 18 pages (incl. Title page). No figure
The GRA Beam-Splitter Experiments and Particle-Wave Duality of Light
Grangier, Roger and Aspect (GRA) performed a beam-splitter experiment to
demonstrate the particle behaviour of light and a Mach-Zehnder interferometer
experiment to demonstrate the wave behaviour of light. The distinguishing
feature of these experiments is the use of a gating system to produce near
ideal single photon states. With the demonstration of both wave and particle
behaviour (in two mutually exclusive experiments) they claim to have
demonstrated the dual particle-wave behaviour of light and hence to have
confirmed Bohr's principle of complementarity. The demonstration of the wave
behaviour of light is not in dispute. But we want to demonstrate, contrary to
the claims of GRA, that their beam-splitter experiment does not conclusively
confirm the particle behaviour of light, and hence does not confirm
particle-wave duality, nor, more generally, does it confirm complementarity.
Our demonstration consists of providing a detailed model based on the Causal
Interpretation of Quantum Fields (CIEM), which does not involve the particle
concept, of GRA's which-path experiment. We will also give a brief outline of a
CIEM model for the second, interference, GRA experiment.Comment: 24 pages, 4 figure
Ensembles and experiments in classical and quantum physics
A philosophically consistent axiomatic approach to classical and quantum
mechanics is given. The approach realizes a strong formal implementation of
Bohr's correspondence principle. In all instances, classical and quantum
concepts are fully parallel: the same general theory has a classical
realization and a quantum realization.
Extending the `probability via expectation' approach of Whittle to
noncommuting quantities, this paper defines quantities, ensembles, and
experiments as mathematical concepts and shows how to model complementarity,
uncertainty, probability, nonlocality and dynamics in these terms. The approach
carries no connotation of unlimited repeatability; hence it can be applied to
unique systems such as the universe.
Consistent experiments provide an elegant solution to the reality problem,
confirming the insistence of the orthodox Copenhagen interpretation on that
there is nothing but ensembles, while avoiding its elusive reality picture. The
weak law of large numbers explains the emergence of classical properties for
macroscopic systems.Comment: 56 page
The Iowa Homemaker vol.3, no.9
Table of Contents
Books – Why Not? by Charles H. Brown, page 3
A Visit to the Bazaars of Stamboul by Eda Lord Murphy, page 4
Glimpses in a Christmas Shop by Helen Brennan, page 4
That Roast Fowl by Viola M. Bell, page 5
Echoes from State Home Economics Convention by Katherine Goeppinger, page 6
Toys That Interest by Bertha Mann, page 7
Christmas Festivities in Foreign Lands by Barbara Dewell, page 8
Christmas Dinner for Two – by Louise Doole, page 9
Italian Hemstitching by Lora Ann Stanke, page 10
Eda Lord Murphy Writes from Constantinople by Eda Lord Murphy, page 10
Who is Responsible for the Child? by Minne Elisabeth Allen, page 11
Holiday Sweets by Alma Riemenschneider, page 12
The Perfect Guest by Lucile Barta, page 12
The Evolution of Home Economics at Iowa State by Ruth Elaine Wilson, page 13
Baskets Which Will Lead Long Useful Lives by Viola Jammer, page 14
Who’s There and Where by Helen I. Putnam, page 1
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