48,415 research outputs found
Simple applications of Noether's first theorem in quantum mechanics and electromagnetism
Internal global symmetries exist for the free non-relativistic
Schr\"{o}dinger particle, whose associated Noether charges--the space integrals
of the wavefunction and the wavefunction multiplied by the spatial
coordinate--are exhibited. Analogous symmetries in classical electromagnetism
are also demonstrated.Comment: 12 page
The origins of length contraction: I. The FitzGerald-Lorentz deformation
One of the widespread confusions concerning the history of the 1887 Michelson-Morley experiment has to do with the initial explanation of this celebrated null result due independently to FitzGerald and Lorentz. In neither case was a strict, longitudinal length contraction hypothesis invoked, as is commonly supposed. Lorentz postulated, particularly in 1895, any one of a certain family of possible deformation effects for rigid bodies in motion, including purely transverse alteration, and expansion as well as contraction; FitzGerald may well have had the same family in mind. A careful analysis of the Michelson-Morley experiment (which reveals a number of serious inadequacies in many text-book treatments) indeed shows that strict contraction is not require
Aspects of Objectivity in Quantum Mechanics
The purpose of the paper is to explore different aspects of the covariance of (mostly) non-relativistic quantum mechanics. First, doubts are expressed concerning the claim that gauge fields can be 'generated' by way of imposition of (local) gauge covariance of the single-particle wave equation. Then a brief review is given of Galilean covariance in the general case of external fields, and the connection between Galilean boosts and gauge transformations. Under time-dependent translations (and hence non-instantaneous boosts) the geometric phase associated with Schrödinger evolution is non-invariant, and the significance of this result is briefly analysed. The covariance properties of Schrödinger dynamics are then brought to bear on certain versions of the modal interpretation of quantum mechanics. The conclusion that it is only relational properties that can be considered coordinate- or gauge-independent elements of reality is reinforced by appeal to the theory of quantum reference frames due to Aharonov and Kauffher. (This paper appeared in "From Physics to Philosophy", J. Butterfield and C. Pagonis (eds.), Cambridge University Press (1999); pp. 45-70.
The origins of length contraction: I. The FitzGerald-Lorentz deformation hypothesis
One of the widespread confusions concerning the history of the 1887
Michelson-Morley experiment has to do with the initial explanation of this
celebrated null result due independently to FitzGerald and Lorentz. In neither
case was a strict, longitudinal length contraction hypothesis invoked, as is
commonly supposed. Lorentz postulated, particularly in 1895, any one of a
certain family of possible deformation effects for rigid bodies in motion,
including purely transverse alteration, and expansion as well as contraction;
FitzGerald may well have had the same family in mind. A careful analysis of the
Michelson-Morley experiment (which reveals a number of serious inadequacies in
many text-book treatments) indeed shows that strict contraction is not
required.Comment: 29 pages; accepted April 2001 for publication in American Journal of
Physic
ROLE OF COUNTY COMMISSIONERS: POLICY MAKING V. ADMINISTRATION AND SERVING ON STATUTORY BOARDS AND COMMISSIONS
Defines the responsibilities of county commissioners and discusses roles as policy makers versus administrators.Public Economics,
SUMMARY OF CONDITIONAL LAND TRANSFER AGREEMENTS
Brief history of P.A. 425 of 1984, discussion of contract provisions, tabular summaries of agreements filed since 1985 and analysis of emerging issues.Land Economics/Use,
POLICY DEPENDENCY AND REFORM: ECONOMIC GAINS VERSUS POLITICAL PAINS
Economic analysis condemns market intervention in favour of farmers as inefficient, if not also ineffective, and therefore well worth reform. Practical experience, however, indicates that such lessons are hard to learn and implement. Part of the reason appears to be that economic analysis seldom clearly identifies the real costs and benefits of reform, and seldom explains these sensibly to the relevant constituencies. Furthermore, economic analysis rarely explains why the protectionist measures were adopted in the first place, or explores the dependencies that these policies generate. Without these explanations, and without reform strategies that take full account of them, policy reform will continue to be reluctant, slow and frequently counterproductive. This paper reconsiders the evolution of farm policies and the economic assessment of their costs and benefits, and draws conclusions as to the general shape of reforms likely to reconcile economic efficiency with political acceptability. In so doing, it re-phrases conventional economic arguments in terms which seem to accord better with sensible intuition, which may prove more accessible and credible to policy makers and advisors. It concludes with a substantial challenge to the agricultural economics profession.Political Economy,
JOINT PUBLIC VENTURES COST ALLOCATION: ALTERNATIVE AND CONSEQUENCES
An in depth discussion of the nature, structure and financing of intergovernmental arrangements in the production of public services. Includes economic justification, methods of allocating costs and examples of joint ventures.Public Economics,
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