Non-abelian vortices on CP^1 and Grassmannians

Many properties of the moduli space of abelian vortices on a compact Riemann surface are known. For non-abelian vortices the moduli space is less well understood. Here we consider non-abelian vortices on the Riemann sphere CP^1, and we study their moduli spaces near the Bradlow limit. We give an explicit description of the moduli space as a Kahler quotient of a finite-dimensional linear space. The dimensions of some of these moduli spaces are derived. Strikingly, there exist non-abelian vortex configurations on CP^1, with non-trivial vortex number, for which the moduli space is a point. This is in stark contrast to the moduli space of abelian vortices. For a special class of non-abelian vortices the moduli space is a Grassmannian, and the metric near the Bradlow limit is a natural generalization of the Fubini--Study metric on complex projective space. We use this metric to investigate the statistical mechanics of non-abelian vortices. The partition function is found to be analogous to the one for abelian vortices.Comment: minor corrections; some notation improve

Letter Written by Norman A. Garrigus to the Bryant College Service Club Dated December 9, 1943

[Transcription begins]UNITED STATES NAVY December 9, 1943 Dear Friends: I received your Christmas package before I left the states but am just now getting the pleasure of thanking you for it. Seeing as how Santa Clause [sic] has already been good to me I hope you won\u27t think that my asking for more candy is an attempt at a second celebration. But when my name comes up on the list again I would appreciate anything you sent. You might be interested to know that the first day I hit port I happened to meet Shirley Dyer and I hope to see her again soon if they aren\u27t going to work me too hard. Things are going to be fine in this duty from all that I can judge in my first few days of it. Many thanks to all and a Merry Christmas. SincerelyNorman A Garrigus[Transcription ends

Paired and interacting galaxies: Conference summary

The author gives a summary of the conference proceedings. The conference began with the presentation of the basic data sets on pairs, groups, and interacting galaxies with the latter being further discussed with respect to both global properties and properties of the galactic nuclei. Then followed the theory, modelling and interpretation using analytic techniques, simulations and general modelling for spirals and ellipticals, starbursts and active galactic nuclei. Before the conference the author wrote down the three questions concerning pairs, groups and interacting galaxies that he hoped would be answered at the meeting: (1) How do they form, including the role of initial conditions, the importance of subclustering, the evolution of groups to compact groups, and the fate of compact groups; (2) How do they evolve, including issues such as relevant timescales, the role of halos and the problem of overmerging, the triggering and enhancement of star formation and activity in the galactic nuclei, and the relative importance of dwarf versus giant encounters; and (3) Are they important, including the frequency of pairs and interactions, whether merging and interactions are very important aspects of the life of a normal galaxy at formation, during its evolution, in forming bars, shells, rings, bulges, etc., and in the formation and evolution of active galaxies? Where possible he focuses on these three central issues in the summary

THE UNFINISHED BUSINESS OF DIPLOMACY

International Relations/Trade,

A ladder of topologically non-trivial non-BPS states

We consider a simple quiver gauge theory with gauge group U(r1) x U(r2) and a Higgs field in the bi-fundamental representation. The back-ground for this theory is a compact K\"ahler manifold M. For a careful but natural choice of Higgs field potential the second order field equations can be replaced with a set of first order BPS equations. We show that the theory admits two energy gaps: The vacuum is topologically trivial but has finite, non-zero energy and is not a BPS state. The second gap lies between the vacuum and the first BPS state. In this gap we find a ladder of states with non-trivial topology, at equidistant energy levels. We give a semi-explicit construction for such topologically non-trivial non-BPS states.Comment: 20 pages, 2 figure

The problem of automation: Inappropriate feedback and interaction, not overautomation

As automation increasingly takes its place in industry, especially high-risk industry, it is often blamed for causing harm and increasing the chance of human error when failures occur. It is proposed that the problem is not the presence of automation, but rather its inappropriate design. The problem is that the operations are performed appropriately under normal conditions, but there is inadequate feedback and interaction with the humans who must control the overall conduct of the task. When the situations exceed the capabilities of the automatic equipment, then the inadequate feedback leads to difficulties for the human controllers. The problem is that the automation is at an intermediate level of intelligence, powerful enough to take over control that which used to be done by people, but not powerful enough to handle all abnormalities. Moreover, its level of intelligence is insufficient to provide the continual, appropriate feedback that occurs naturally among human operators. To solve this problem, the automation should either be made less intelligent or more so, but the current level is quite inappropriate. The overall message is that it is possible to reduce error through appropriate design considerations

Review of river fisheries valuation in tropical Asia

This study attempts to estimate the economic value of riverine fisheries in tropical Asia and quantify the economic impacts of any changes to the environment that affects rivers and hence fisheries. The value of riverine fisheries has been considered in the following two ways: firstly, through a compilation and summary of the results of existing studies on this topic; secondly, by estimating the direct use value of riverine and floodplain fishing by country using quantities and freshwater fish prices derived from various sources. Furthermore, a review of the characteristics of the fisheries is presented. These fisheries have been shown to be valuable (i.e., economically or socially important) in at least two specific ways: as a generator of commercially marketable output, and as a source of income and employment in relatively impoverished communities

Zero torque gear head wrench

A gear head wrench particularly suited for use in applying torque to bolts without transferring torsional stress to bolt-receiving structures is introduced. The wrench is characterized by a coupling including a socket, for connecting a bolt head with a torque multiplying gear train, provided within a housing having an annulus concentrically related to the socket and adapted to be coupled with a spacer interposed between the bolt head and the juxtaposed surface of the bolt-receiving structure for applying a balancing counter-torque to the spacer as torque is applied to the bolt head whereby the bolt-receiving structure is substantially isolated from torsional stress. As a result of the foregoing, the operator of the wrench is substantially isolated from any forces which may be imposed