Dynamics, correlations and phases of the micromaser

The micromaser possesses a variety of dynamical phase transitions parametrized by the flux of atoms and the time-of-flight of the atom within the cavity. We discuss how these phases may be revealed to an observer outside the cavity using the long-time correlation length in the atomic beam. Some of the phase transitions are not reflected in the average excitation level of the outgoing atom, which is the commonly used observable. The correlation length is directly related to the leading eigenvalue of the time evolution operator, which we study in order to elucidate the phase structure. We find that as a function of the time-of-flight the transition from the thermal to the maser phase is characterized by a sharp peak in the correlation length. For longer times-of-flight there is a transition to a phase where the correlation length grows exponentially with the flux. We present a detailed numerical and analytical treatment of the different phases and discuss the physics behind them.Comment: 60 pages, 18 figure files, Latex + \special{} for the figures, (some redundant figures are eliminated and others are changed

Coherent states for exactly solvable potentials

A general algebraic procedure for constructing coherent states of a wide class of exactly solvable potentials e.g., Morse and P{\"o}schl-Teller, is given. The method, {\it a priori}, is potential independent and connects with earlier developed ones, including the oscillator based approaches for coherent states and their generalizations. This approach can be straightforwardly extended to construct more general coherent states for the quantum mechanical potential problems, like the nonlinear coherent states for the oscillators. The time evolution properties of some of these coherent states, show revival and fractional revival, as manifested in the autocorrelation functions, as well as, in the quantum carpet structures.Comment: 11 pages, 4 eps figures, uses graphicx packag

Effect of Viewing Angle on Luminance and Contrast for a Five-Million-Pixel Monochrome Display and a Nine-Million-Pixel Color Liquid Crystal Display

Digital imaging systems used in radiology rely on electronic display devices to present images to human observers. Active-matrix liquid crystal displays (AMLCDs) continue to improve and are beginning to be considered for diagnostic image display. In spite of recent progress, AMLCDs are characterized by a change in luminance and contrast response with changes in viewing direction. In this article, we characterize high pixel density AMLCDs (a five-million-pixel monochrome display and a nine-million-pixel color display) in terms of the effect of viewing angle on their luminance and contrast response. We measured angular luminance profiles using a custom-made computer-controlled goniometric instrument and a conoscopic Fourier-optics instrument. We show the angular luminance response as a function of viewing angle, as well as the departure of the measured contrast from the desired response. Our findings indicate small differences between the five-million-pixel (5 MP) and the nine-million-pixel (9 MP) AMLCDs. The 9 MP shows lower variance in contrast with changes in viewing angle, whereas the 5 MP provides a slightly better GSDF compliance for off-normal viewing

Comparison of Human Observer Performance of Contrast-Detail Detection Across Multiple Liquid Crystal Displays

Appropriate selection of a display subsystem requires balancing the optimization of its physical parameters with clinical setting and cost. Recent advances in Liquid Crystal Display (LCD) technology warrant a rigorous evaluation of both the specialized and the mass market displays for clinical radiology. This article outlines step two in the evaluation of a novel 9.2 million pixel IBM AMLCD panel. Prior to these experiments, the panel was calibrated according to the DICOM Part 14 standard, using both a gray-scale and a pseudo-gray scale lookup table. The specific aim of this study is to compare human, contrast-detail perception on different computer display subsystems. The subsystems that we looked at included 3- and 5-million pixel “medical-grade” monochrome LCDs and a 9.2-million pixel color LCD. We found that the observer response was similar for these three display configurations

Medical Grade vs Off-the-Shelf Color Displays: Influence on Observer Performance and Visual Search

The goal of this study was to compare diagnostic accuracy of radiologists viewing clinical images on a top-of-the-line medical-grade vs a top-of-the-line commercial off-the-shelf (COTS) color display with the luminance values set to simulate a display that had been in use for 1 year. A set of 50 digital radiography chest images was selected for use in the study, half containing a solitary pulmonary nodule and half nodule-free. The images were displayed twice to each of six observers, once on each display. Eye position was recorded on a subset of the images. Overall, there was a statistically significant difference (F = 4.1496, p = 0.0471) between the medical-grade color display and the COTS color display in terms of receiver operating characteristic area under the curve values, with the medical-grade display yielding higher diagnostic accuracy. Total viewing time did not differ significantly, but eye position data revealed differences, suggesting better search and decision-making efficiency with the medical-grade display. Medical-grade color displays at 1 year old yield better diagnostic and search efficiency than COTS color displays and thus are recommended for primary reading if color displays are to be used