An alternative approach to equivariant stable homotopy theory

Building on the work of Martin Stolz, we develop the basics of equivariant stable homotopy theory starting from the simple idea that a G- spectrum should just be a spectrum with an action of G on it, in contrast to the usual approach in which the definition of a G-spectrum depends on a choice of universe.Comment: 14 page

Strategic Trade Policy with Polynomial Costs

 We investigate how the superiority of the optimal subsidy or tariff in an international Cournot oligopoly depends on the production technology used in the industry, an interesting issue that has not been analyzed in the literature. We establish that the welfare superiority of the optimal subsidy or tariff depends on the relative steepness of the firms' common marginal cost curve: when it is relatively steep, tariffs are superior to subsidies in enhancing domestic welfare, and vice versa. When both instruments are used simultaneously, the tariff component becomes more important as the marginal cost curve steepens.

RFID in the supply chain: lessons from European early adopters

Purpose Radio frequency identification (RFID) is increasingly being presented as a technology with the potential to improve supply chain performance, but empirical evidence from early adopters is sparse. This paper aims to rectify this scarcity and contribute to a more informed discussion in and between academic and practitioner communities. Design/Methodology/Approach The paper is based on a conceptual model of factors influencing the success of adoption efforts. It then reports the results of a survey of 612 European supply chain managers, focusing on the 128 respondents who have begun RFID trials. Findings A significant influence on operational deployment is the presence of mandates from key customers requiring the technology’s use. Customer mandates also impact the anticipated benefits of a faster sales cycle and of enhanced systems integration, though the relationships are complex. By contrast, greater cost reduction benefits are anticipated in two industries where mandates are less common – industrial goods and logistics. Perceived organizational innovativeness positively impacts anticipated ROI from RFID. Companies adopting a ‘slap and ship’ approach are less likely to anticipate pricing benefits than those integrating RFID into enterprise systems Research Limitations/Implications The limitations of the paper include the limited sample size of early adopters. In addition, qualitative research is needed into RFID supply chain applications and into different approaches to IS integration of RFID, to inform future survey work. Practical Implications This paper informs supply chain managers and senior decision makers who are examining the potential of RFID technology. It offers guidance on what issues to look for when adopting this technology, approaches to take and the benefits that might be accrued. Originality/Valuer This paper offers a major contribution to understanding the current status of the adoption of RFID in European supply chains. This understanding is put in the context of the wider literatures on supply chain management and the adoption of information systems and te

"Sample Variance" in Small-Scale CMB Anisotropy Experiments

We discuss the effects of finite sky coverage and the uncertainty in extracting information about the power spectrum from experiments on small angular scales. In general the cosmic variance is enhanced by a factor of $4\pi/A$, where $A$ is the solid angle sampled by the experiment. As a rough guide, an experiment with sensitivity peaking at the $\ell$th multipole has to cover \simgt\ell independent patches to have a lower ``sample variance'' than for a whole-sky measurement of the quadrupole. Our approach gives a relatively simple way of attaching an error bar to the theoretical prediction for a particular experiment, and thereby comparing theories with experimental results, without the need for computationally-intensive Maximum Likelihood or Monte Carlo calculations.Comment: 6 pages in Plain TeX with 1 postscript figure appende

Non-isothermal X-ray Emitting Gas in Clusters of Galaxies

We have analyzed X-ray spectra from six galaxy clusters which contain cooling flows: A85, A478, A1795, A2142, A2147, & A2199. The X-ray spectra were taken with the HEAO1-A2 Medium and High Energy Detectors and the Einstein Solid State Spectrometer. For each cluster, we simultaneously fit the spectra from these three detectors with models incorporating one or more emission components comprised of either thermal or cooling flow models. Five of the clusters (all but A2142) are better fit by a multi-component model (a cooling flow plus one or two thermal components or a two thermal component model) than by isothermal models. In four of the clusters (A85, A1795, A2147, & A2199), we find evidence for cool gas outside of the canonical cooling flow region. These latter four clusters can be characterized by three temperature components: a temperature inversion in the central region, a hotter region with an emission-weighted temperature which is higher than that of an isothermal model fit to the entire cluster, and a cooler region with an emission-weighted temperature of ~1 keV. The cool component outside the cooling flow region has a large minimum emission measure which we attribute, in part, to diffuse cool gas in the outer cluster atmosphere. If at least some of the cool exterior gas is virialized, this would imply a radially decreasing temperature profile. Together with the density profiles we have found, this leads to a baryon fraction in gas which increases with radius and is larger than that for an isothermal cluster atmosphere. Consequently, if clusters of galaxies trace the mass distribution in the Universe, the gas mass fraction we have calculated for an isothermal gas (which is ~15%) together with the nominal galaxy contribution (~5%) gives a baryon fraction of ~20%. Using the upper limit to the baryon density derived from BigComment: gzipped tar file of 26 PostScript pages, including 2 figures, 7 tables. Also available at http://www.astr.ua.edu/preprints/white/INDEX_READ_ME_1st.htm

Relic density and CMB constraints on dark matter annihilation with Sommerfeld enhancement

We calculate how the relic density of dark matter particles is altered when their annihilation is enhanced by the Sommerfeld mechanism due to a Yukawa interaction between the annihilating particles. Maintaining a dark matter abundance consistent with current observational bounds requires the normalization of the s-wave annihilation cross section to be decreased compared to a model without enhancement. The level of suppression depends on the specific parameters of the particle model, with the kinetic decoupling temperature having the most effect. We find that the cross section can be reduced by as much as an order of magnitude for extreme cases. We also compute the mu-type distortion of the CMB energy spectrum caused by energy injection from such Sommerfeld-enhanced annihilation. Our results indicate that in the vicinity of resonances, associated with bound states, distortions can be large enough to be excluded by the upper limit |mu|<9.0x10^(-5) found by the COBE/FIRAS experiment.Comment: 10 pages, 6 figures, accepted for publication in Physical Review D. Corrections to eqs. 9,10,14 and 16. Figures updated accordingly. No major changes to previous results. Website with online tools for Sommerfeld-related calculations can be found at http://www.mpa-garching.mpg.de/~vogelsma/sommerfeld

Towards a Molecular Inventory of Protostellar Discs

The chemical environment in circumstellar discs is a unique diagnostic of the thermal, physical and chemical environment. In this paper we examine the structure of star formation regions giving rise to low mass stars, and the chemical environment inside them, and the circumstellar discs around the developing stars.Comment: 9 page PDF, 550 kbyte