The winner's curse: experiments with buyers and with sellers

This paper explores the winner's curse phenomena as it was studied experimentally by Kagel and Levin. Experiments with the winner's curse are complicated by the fact that subjects can lose money and the experimenter has only a limited means of collecting it from them. Thus subjects enjoy only limited liability which has theoretical implications for behavior. In the Kagel and Levin experiments subjects were removed from the bidders' competition after losses reached a predetermined value. This experimental procedure has unknown implications for the results so ambiguity exists about whether the winner's curse was actually observed. In this study their results were replicated in an environment in which subjects were not removed. The case in which competitors are sellers is also studied. Bankruptcy cannot be a problem in sellers' competition. In both cases the winner's curse is observed. Thus the limited liability cannot be an explanation for the phenomenon reported by Kagel and Levin. In addition the paper examines the bidding behavior of all individuals and shows that this behavior does not fit any of the tested theories either on the aggregate or individual level. The "winner's curse" did not disappear over time during the conduct of the research

Communication Channel Usage: Is There a Gender Difference?

The object of this paper is to investigate the proposition that communication channel usage differs by gender. First the results of a communication channel study are reported which examined perceptions of communication channel usage in a group of office workers. These results are then explained in the light of existing information processing theory. While these findings are limited in generalizability, this study shows the lack of gender specific information processing research. Researchers may find it useful when examining information processing and communication channel usage, in particular, to control for gender differences

The Effectiveness of Electronic Work Groups for Student Cases

During the last two years in the case based, upper level undergraduate Management Information Systems Course that I teach, I have included segments in the course to provide opportunities for the students to use the Internet: (1) email for distribution of course assignments and (2) gopher and World Wide Web browers to find information to supplement case work. As a result of a call from a distribution list, I volunteered my class to participate in collaborative case work using the Internet with universities in Canada, United States, and Mexico: University of Washington, University of Nebraska -Lincoln, University of Oregon, Rowan College, University of Idaho, University of Tennessee at Knoxville, McGill University, Monterrey Institute of Technology and Higher Education, Stephen F. Austin State University, University of Prince Edward Island. Three cases were considered by the faculty at these universities and finally a case about Microsoft Corporation was selected and questions to be answered were agreed upon. At these universities, the students were either taking an organizational strategy course oran MIS course. In this paper, the process of establishing these collaborative, Internet case groups is discussed. Also the students rated their experience using the Internet case group versus a face-to-face case group they used for a later case assignment about Sun Microsystems

Mechanisms for Lasing with Cold Atoms as the Gain Medium

We realize a laser with a cloud of cold rubidium atoms as gain medium, placed in a low-finesse cavity. Three different regimes of laser emission are observed corresponding respectively to Mollow, Raman and Four Wave Mixing mechanisms. We measure an output power of up to 300 $\mu$W and present the main properties of these different lasers in each regime

Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation

Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and local thermodynamic equilibrium (LTE) is still unclear. To investigate this, we carry out 3D non-LTE calculations for the Balmer lines, performed, for the first time, over an extensive grid of 3D hydrodynamic STAGGER model atmospheres. For H$\alpha$, H$\beta$, and H$\gamma$, we find significant 1D non-LTE versus 3D non-LTE differences (3D effects): the outer wings tend to be stronger in 3D models, particularly for H$\gamma$, while the inner wings can be weaker in 3D models, particularly for H$\alpha$. For H$\alpha$, we also find significant 3D LTE versus 3D non-LTE differences (non-LTE effects): in warmer stars ($T_{\text{eff}}\approx6500$K) the inner wings tend to be weaker in non-LTE models, while at lower effective temperatures ($T_{\text{eff}}\approx4500$K) the inner wings can be stronger in non-LTE models; the non-LTE effects are more severe at lower metallicities. We test our 3D non-LTE models against observations of well-studied benchmark stars. For the Sun, we infer concordant effective temperatures from H$\alpha$, H$\beta$, and H$\gamma$; however the value is too low by around 50K which could signal residual modelling shortcomings. For other benchmark stars, our 3D non-LTE models generally reproduce the effective temperatures to within $1\sigma$ uncertainties. For H$\alpha$, the absolute 3D effects and non-LTE effects can separately reach around 100K, in terms of inferred effective temperatures. For metal-poor turn-off stars, 1D LTE models of H$\alpha$ can underestimate effective temperatures by around 150K. Our 3D non-LTE model spectra are publicly available, and can be used for more reliable spectroscopic effective temperature determinations.Comment: 19 pages, 10 figures, abstract abridged; accepted for publication in Astronomy & Astrophysic

Shear free, twisting Einstein-Maxwell metrics in the Newman-Penrose formalism

The problem of finding algebraically special solutions to the vacuum Einstein-Maxwell equations was investigated using a spin coefficient formalism. The general case in which the degenerate null vectors are not hypersurface orthogonal is reduced to a problem of solving five coupled differential equations that are no longer dependent on the affine parameter along the degenerate null directions. It is shown that the most general regular, shear-free, nonradiating solution to these equations is the Kerr-Newman metric

Electrodynamic Radiation Reaction and General Relativity

We argue that the well-known problem of the instabilities associated with the self-forces (radiation reaction forces) in classical electrodynamics are possibly stabilized by the introduction of gravitational forces via general relativity