Quantum mechanics with time-dependent parameters

Smooth composite bundles provide the adequate geometric description of classical mechanics with time-dependent parameters. We show that the Berry's phase phenomenon is described in terms of connections on composite Hilbert space bundles.Comment: 7 pages, LaTe

MAST: Mental Ambidexterity in Strategic Thinking

There are two fundamental ways to think about what strategy is. The first one is strategy as a plan of action for reaching one or several goals. The second one is strategy as discipline, a formalized body of knowledge. The latter can be understood as the set of governing ideas that guide managers in the identification of opportunities for value creation and the realization of that value. In the present article, we argue that these ideas tend to fall into two main paradigms, which come with two metaphors about managers: managers as commanders and managers as designers. We further argue that these represent two fundamental ways of thinking, which in turn become ways of ‘seeing’ and even feeling. Is one better than the other? We suggest that is not the right question to ask. Rather it is important to appreciate that these are worldviews that affect how we interpret our day-to-day reality and our ability to see opportunities. We introduce the notion of Mental Ambidexterity in Strategic Thinking (MAST) and define it as the ability to hold both views of the world—that of the commander and that of the designer— and play with them simultaneously, rather than focusing solely on one and rejecting the other. MAST is an individual level capability; it is a flexible, non-ideological and fluid mode of cognition. At the core, it is characterized by switching flexibility back and forth between rational decisionmaking among alternatives, and creation of new alternatives, between what is and what could be. We illustrate three principles – i) intellectual humility, ii) contingent thinking and iii) poke into ambiguity – that act as catalysts for individuals to develop MAST capabilities

A recalibration of IUE NEWSIPS low dispersion data

While the low dispersion IUE NEWSIPS data products represent a significant improvement over original IUE SIPS data, they still contain serious systematic effects which compromise their utility for certain applications. We show that NEWSIPS low resolution data are internally consistent to only 10-15% at best, with the majority of the problem due to time dependent systematic effects. In addition, the NEWSIPS flux calibration is shown to be inconsistent by nearly 10%. We examine the origin of these problems and proceed to formulate and apply algorithms to correct them to ~ 3% level -- a factor of 5 improvement in accuracy. Because of the temporal systematics, transforming the corrected data to the IUE flux calibration becomes ambiguous. Therefore, we elect to transform the corrected data onto the HST FOS system. This system is far more self-consistent, and transforming the IUE data to it places data from both telescopes on a single system. Finally, we argue that much of the remaining 3% systematic effects in the corrected data is traceable to problems with the NEWSIPS intensity transformation function (ITF). The accuracy could probably be doubled by rederiving the ITF.Comment: Submitted to ApJ Supplement, 35 pages, 13 figures, LaTeX - AASTEX aas2pp4.st

Quantile Regression Estimates of Confidence Intervals for WASDE Price Forecasts

This study uses quantile regressions to estimate historical forecast error distributions for WASDE forecasts of corn, soybean, and wheat prices, and then compute confidence limits for the forecasts based on the empirical distributions. Quantile regressions with fit errors expressed as a function of forecast lead time are consistent with theoretical forecast variance expressions while avoiding assumptions of normality and optimality. Based on out-of-sample accuracy tests over 1995/96–2006/07, quantile regression methods produced intervals consistent with the target confidence level. Overall, this study demonstrates that empirical approaches may be used to construct accurate confidence intervals for WASDE corn, soybean, and wheat price forecasts.commodity, evaluating forecasts, government forecasting, judgmental forecasting, prediction intervals, price forecasting, Crop Production/Industries, Demand and Price Analysis,

Signature of wide-spread clumping in B supergiant winds

We seek to establish additional observational signatures of the effects of clumping in OB star winds. The action of clumping on strategic wind-formed spectral lines is tested to steer the development of models for clumped winds and thus improve the reliability of mass-loss determinations for massive stars.The SiIV 1400 resonance line doublets of B0 to B5 supergiants are analysed using empirical line-synthesis models. The focus is on decoding information on wind clumping from measurements of ratios of the radial optical depths (tau_(rad)(w)) of the red and blue components of the SiIV doublet. We exploit in particular the fact that the two doublet components are decoupled and formed independently for targets with relatively low wind terminal velocities. Line-synthesis analyses reveal that the mean ratio of tau_(rad)(w) of the blue to red SiIV components are rarely close to the canonical value of ~ 2 (expected from atomic constants), and spread instead over a range of values between ~1 and 2. These results are interpreted in terms of a photosphere that is partially obscured by optically thick structures in the outflowing gas.The spectroscopic signatures established in this study demonstrate the wide-spread existence of wind clumping in B supergiants. The additional information in unsaturated doublet profiles provides a means to quantify the porosity of the winds.Comment: Accepted for publication in A&A Letter

An analysis of the shapes of interstellar extinction curves. VII Milky Way spectrophotometric optical-through-ultraviolet extinction and its R-dependence

We produce a set of 72 NIR-through-UV extinction curves by combining new Hubble Space Telescope/STIS optical spectrophotometry with existing International Ultraviolet Explorer spectrophotometry (yielding gapless coverage from 1150 to 10000 ?) and NIR photometry. These curves are used to determine a new, internally consistent NIR-through-UV Milky Way mean curve and to characterize how the shapes of the extinction curves depend on R(V). We emphasize that while this dependence captures much of the curve variability, considerable variation remains that is independent of R(V). We use the optical spectrophotometry to verify the presence of structure at intermediate wavelength scales in the curves. The fact that the optical-through-UV portions of the curves are sampled at relatively high resolution makes them very useful for determining how extinction affects different broadband systems, and we provide several examples. Finally, we compare our results to previous investigations

Detection of a Hot Binary Companion of η\eta Carinae

We report the detection of a hot companion of $\eta$ Carinae using high resolution spectra (905 - 1180 \AA) obtained with the Far Ultraviolet Spectroscopic Explorer (\fuse) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from \etacar shortward of \lya disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, \etaB, was also eclipsed by the dense wind or extended atmosphere of \etaA. Analysis of the far-UV spectrum shows that \etaB is a luminous hot star. The \nii \wll1084-1086 emission feature suggests that it may be nitrogen-rich. The observed far-UV flux levels and spectral features, combined with the timing of their disappearance, is consistent with \etacar\ being a massive binary system