Environmental Influences in SGRs and AXPs

Soft gamma-ray repeaters (SGRs) and anomalous x-ray pulsars (AXPs) are young (<100 kyr), radio-quiet, x-ray pulsars which have been rapidly spun-down to slow spin periods clustered at 5-12 s. Nearly all of these unusual pulsars also appear to be associated with supernova shell remnants (SNRs) with typical ages <20 kyr. If the unusual properties of SGRs and AXPs were due to an innate feature, such as a superstrong magnetic field, then the pre-supernova environments of SGRs and AXPs should be typical of neutron star progenitors. This is not the case, however, as we demonstrate that the interstellar media which surrounded the SGR and AXP progenitors and their SNRs were unusually dense compared to the environments around most young radio pulsars and SNRs. Thus, if these SNR associations are real, the SGRs and AXPs can not be ``magnetars'', and we suggest instead that the environments surrounding SGRs and AXPs play a controlling role in their development.Comment: 5 pages with 2 figures. To appear in the proceedings of the 5th Huntsville GRB Symposium (Huntsville, AL, Oct. 1999

Reintegrating the Social Sciences: The Dahlem Group

Social science disciplines see themselves as distinct, with their own territory, their own methods, and their own framework. Within such an environment multidisciplinary work involves enormous conflict and translation problems. This situation is no longer acceptable. Dealing with modern problems requires researchers with broad transdisciplinary knowledge and with the ability to communicate with other social science researchers in a way that will allow them to arrive at transdisciplinary recommendations. Complex issues such as healthcare, income distributions, crime prevention, industrial policy, agriculture require not only insights from multiple social disciplines, but the integration of those insights. This document offers a proposal for training social science researchers. Specifically, it proposes reintegrating the social sciences by modifying the current system of training—which provides completely separate training for researchers in each sub-discipline—to incorporate a common first year “core"of training for all social science researchers. If implemented, the proposal will reduce the babble that currently characterizes much of the interdisciplinary conversations.

The effect of dust scattering on the timing properties of black holes

It has been known that sources with high absorption column density also have high dust column density along the line of sight. The differential delays caused by small angle scattering of X rays by dust may have important effects on the power spectra of Galactic black holes at low energies, and impact studies that use the relation between the rms amplitude of variability and energy to determine the origin of QPOs from these sources. We observed the high absorption column density (NH ˜1023 cm-2 ) GBH 1E1740.7-2942 for 20 ks simultaneously with XMM-Newton and RXTE. By comparing the power spectra from the events in the core of the point spread function (PSF) of XMM-Newton EPIC-PN (using imaging and excluding the scattering halo) and the RXTE data, we quantified the effects of small angle scattering on the timing properties of this source. The rms amplitude of variability in ˜2-6 keV band obtained from the XMM-Newton data is higher than that of the RXTE as expected from the a scattering halo contribution in the RXTE

Sins of the Sons of Samuelson: Vision, Pedagogy, and the Zig-Zag Windings of Complex Dynamics

The standard economics text is centered on a vision of a naturally self-regulated, dynamically stable system with a unique global attractor. This paper discusses how we got there and how recent developments in the study of dynamical systems allow us to go beyond that. It traces the evolution of the teaching of economics from Alfred Marshall, who built his supply-and-demand framework within a complexity vision of the economy. It suggests that that complexity vision was lost as economists formalized the supply- demand framework and extended it to the entire economy. This paper argues that the current textbook presentation of economics should not and cannot serve as the only intellectual frame we provide to our students

Temporal Variations of Strength and Location of the South Atlantic Anomaly as Measured by RXTE

The evolution of the particle background at an altitude of ~540 km during the time interval between 1996 and 2007 is studied using the particle monitor of the High Energy X-ray Timing Experiment on board NASA's Rossi X-ray Timing Explorer. A special emphasis of this study is the location and strength of the South Atlantic Anomaly (SAA). The size and strength of the SAA are anti-correlated with the the 10.7 cm radio flux of the Sun, which leads the SAA strength by ~1 year reflecting variations in solar heating of the upper atmosphere. The location of the SAA is also found to drift westwards with an average drift rate of about 0.3 deg/yr following the drift of the geomagnetic field configuration. Superimposed to this drift rate are irregularities, where the SAA suddenly moves eastwards and where furthermore the speed of the drift changes. The most prominent of these irregularities is found in the second quarter of 2003 and another event took place in 1999. We suggest that these events are previously unrecognized manifestations of the geomagnetic jerks of the Earth's magnetic field.Comment: 21 pages, 11 figures, accepted for publication in Earth and Planetary Science Letter

The Welfare Costs of Market Restrictions

In most introductory and intermediate microeconomics textbooks, the measurable welfare effects of price controls, quantitative restrictions, and market restrictions more generally, are depicted as a Harberger triangle. This depiction understates these restrictions’ inefficiency costs because it captures only the ‘‘top-down’’ distortion caused by the wedge these restrictions drive between market-wide quantity demanded and quantity supplied. It ignores the ‘‘bottom-up’’ distortions caused by allocative inefficiencies on the constrained side of the market. In this article we describe a simple graphical exposition of these bottom-up distortions. We argue that this graph can provide students with a picture of both the top-down and bottom-up inefficiencies. Moreover, it can be used for simple back-of-the-envelope estimates of the magnitudes of the two inefficiencies