On the Quantum Phase Operator for Coherent States

In papers by Lynch [Phys. Rev. A41, 2841 (1990)] and Gerry and Urbanski [Phys. Rev. A42, 662 (1990)] it has been argued that the phase-fluctuation laser experiments of Gerhardt, B\"uchler and Lifkin [Phys. Lett. 49A, 119 (1974)] are in good agreement with the variance of the Pegg-Barnett phase operator for a coherent state, even for a small number of photons. We argue that this is not conclusive. In fact, we show that the variance of the phase in fact depends on the relative phase between the phase of the coherent state and the off-set phase $\phi_0$ of the Pegg-Barnett phase operator. This off-set phase is replaced with the phase of a reference beam in an actual experiment and we show that several choices of such a relative phase can be fitted to the experimental data. We also discuss the Noh, Foug\`{e}res and Mandel [Phys.Rev. A46, 2840 (1992)] relative phase experiment in terms of the Pegg-Barnett phase taking post-selection conditions into account.Comment: 8 pages, 8 figures. Typographical errors and misprints have been corrected. The outline of the paper has also been changed. Physica Scripta (in press

Invariant vector fields and the prolongation method for supersymmetric quantum systems

The kinematical and dynamical symmetries of equations describing the time evolution of quantum systems like the supersymmetric harmonic oscillator in one space dimension and the interaction of a non-relativistic spin one-half particle in a constant magnetic field are reviewed from the point of view of the vector field prolongation method. Generators of supersymmetries are then introduced so that we get Lie superalgebras of symmetries and supersymmetries. This approach does not require the introduction of Grassmann valued differential equations but a specific matrix realization and the concept of dynamical symmetry. The Jaynes-Cummings model and supersymmetric generalizations are then studied. We show how it is closely related to the preceding models. Lie algebras of symmetries and supersymmetries are also obtained.Comment: 37 pages, 7 table

Reducing potentially preventable complications at the multi hospital level

Contains fulltext : 96269.pdf (publisher's version ) (Open Access)ABSTRACT: BACKGROUND: This study describes the continuation of a program to constrain health care costs by limiting inpatient hospital programs among the hospitals of Syracuse, New York. Through a community demonstration project, it identified components of individual hospital programs for reduction of complications and their impact on the frequency and rates of these outcomes. FINDINGS: This study involved the implementation of interventions by three hospitals using the Potentially Preventable Complications System developed by 3M Health Information Systems. The program is noteworthy because it included competing hospitals in the same community working together to reduce adverse patient outcomes and related costs.The study data identified statistically significant reductions in the frequency of high and low volume complications during the three year period at two of the hospitals. At both of these hospitals, aggregate complication rates also declined. At these hospitals, the differences between actual complication rates and severity adjusted complication rates were also reduced.At the third hospital, specific and aggregate complication rates remained the same or increased slightly. Differences between these rates and those of severity adjusted comparison population also remained the same or increased. CONCLUSIONS: Results of the study suggested that, in one community health care system, the progress of reducing complications involved different experiences. At two hospitals with relatively higher rates at the beginning of the study, management by administrative and clinical staff outside quality assurance produced significant reductions in complication rates, while at a hospital with lower rates, management by quality assurance staff had little effect on reducing the rate of PPCs

Dumping on free trade: the US import trade laws

The passage of the Uruguay Round trade agreement represents a natural opportunity for us to review the policy goals of the US import trade laws, to assess how well current laws achieve those objectives, and to explore possible reforms. We argue that there are a variety of policy concerns that militate for a circumscribed set of import trade statutes. The relevant US laws, however, have largely become divorced from such national welfare considerations and are now too often a mechanism for furtive protectionism. The Uruguay Round effected some (marginal) improvements, but left the fundamental structure of the laws unchanged. We discuss possible reforms in the final selection of the paper