Duality, Marginal Perturbations and Gauging

We study duality transformations for two-dimensional sigma models with abelian chiral isometries and prove that generic such transformations are equivalent to integrated marginal perturbations by bilinears in the chiral currents, thus confirming a recent conjecture by Hassan and Sen formulated in the context of Wess-Zumino-Witten models. Specific duality transformations instead give rise to coset models plus free bosons.Comment: 15 page

Peace parks in Southern Africa: bringers of an African renaissance

The pursuit of an African Renaissance has become an important aspect of regional cooperation between South Africa and its neighbours. Transfrontier conservation areas, or ‘Peace Parks’ as they are popularly called, have been identified as key instruments to promote the African Renaissance dream, and are increasingly advocated and justified on this basis. By fostering joint conservation (and tourism) development in Southern Africa’s marginalised border regions, Peace Parks are claimed to further international peace, regional cooperation and poverty reduction, and thus serve basic ideals of the African Renaissance. This article critically explores this assumption. Using the joint South African-Mozambican-Zimbabwean Great Limpopo Park as a case study, it argues that in reality the creation of Peace Parks hardly stimulates and possibly even undermines the realisation of the African Renaissance ideals of regional cooperation, emancipation, cultural reaffirmation, sustainable economic development and democratisation. So far, their achievement has been severely hindered by domination of national interests, insufficient community consultation, and sensitive border issues such as the illegal flows of goods and migrants between South Africa and neighbouring countries. Furthermore, exacerbation of inter-state differences induced by power imbalances in the region, and harmonisation of land use and legal systems across boundaries, are increasingly becoming sources of conflict and controversy. Some of these problems are so severe, we conclude, that they might eventually even undermine support for African Renaissance as a whole. Utmost care is thus required to optimally use the chances that Peace Parks do offer in furthering an African Renaissance

Complexified sigma model and duality

We show that the equations of motion associated with a complexified sigma-model action do not admit manifest dual SO(n,n) symmetry. In the process we discover new type of numbers which we called `complexoids' in order to emphasize their close relation with both complex numbers and matroids. It turns out that the complexoids allow to consider the analogue of the complexified sigma-model action but with (1+1)-worldsheet metric, instead of Euclidean-worldsheet metric. Our observations can be useful for further developments of complexified quantum mechanics.Comment: 15 pages, Latex, improved versio

T-Duality For String in Horava-Lifshitz Gravity

We continue our study of the Lorentz breaking string theories. These theories are defined as string theory with modified Hamiltonian constraint which breaks the Lorentz symmetry of target space-time. We analyze properties of this theory in the target space-time that possesses isometry along one direction. We also derive the T-duality rules for Lorentz breaking string theories and show that they are the same as that of Buscher's T-duality for the relativistic strings.Comment: 17 pages, references adde

Sigma models with non-commuting complex structures and extended supersymmetry

We discuss additional supersymmetries for N = (2, 2) supersymmetric non-linear sigma models described by left and right semichiral superfields.Comment: 11 pages. Talk presented by U.L. at "30th Winter School on Geometry and Physics" Srni, Czech Republic January 2010

Duality Versus Supersymmetry and Compactification

We study the interplay between T-duality, compactification and supersymmetry. We prove that when the original configuration has unbroken space-time supersymmetries, the dual configuration also does if a special condition is met: the Killing spinors of the original configuration have to be independent on the coordinate which corresponds to the isometry direction of the bosonic fields used for duality. Examples of ``losers" (T-duals are not supersymmetric) and ``winners" (T-duals are supersymmetric) are given.Comment: LaTeX file, 19 pages, U. of Groningen Report UG-8/94, Stanford U. Report SU-ITP-94-19, QMW College Report QMW-PH-94-1

A multivariate analysis of enlisted attrition in the Army Reserve

The purpose of this thesis was to investigate determinants of early attrition from the U.S. Army Selected Reserve enlisted forces. The sample was selected from fiscal year 1980 through 1982 cohort files maintained by the Defense Manpower Data Center. Selected Reserve enlisted personnel were divided into non-prior and prior service groups. Preliminary analyses were performed which identified significant differences between the two groups relative to the timing and destination of attrition losses. Bivariate analyses of stayer/ leaver subgroups revealed significant differences on selected personal and occupational characteristics. Regression analyses were used to examine the influence of candidate explanatory variables on the logistic form of attrition. The variables examined were found to be significant in the analytical results; however, low explanatory power of the models tested indicated a need for reconfiguration of the data base to support future research.http://archive.org/details/multivariateanal00albiLieutenant, United States NavyApproved for public release; distribution is unlimited

Branes, Times and Dualities

Dualities link M-theory, the 10+1 dimensional strong coupling limit of the IIA string, to other 11-dimensional theories in signatures 9+2 and 6+5, and to type II string theories in all 10-dimensional signatures. We study the Freund-Rubin-type compactifications and brane-type solutions of these theories, and find that branes with various world-volume signatures are possible. For example, the 9+2 dimensional M* theory has membrane-type solutions with world-volumes of signature (3,0) and (1,2), and a solitonic solution with world-volume signature (5,1).Comment: 36 pages, 4 Postscript figures, uses harvmac macr

Michelson Interferometry with the Keck I Telescope

We report the first use of Michelson interferometry on the Keck I telescope for diffraction-limited imaging in the near infrared JHK and L bands. By using an aperture mask located close to the f/25 secondary, the 10 m Keck primary mirror was transformed into a separate-element, multiple aperture interferometer. This has allowed diffraction-limited imaging of a large number of bright astrophysical targets, including the geometrically complex dust envelopes around a number of evolved stars. The successful restoration of these images, with dynamic ranges in excess of 200:1, highlights the significant capabilities of sparse aperture imaging as compared with more conventional filled-pupil speckle imaging for the class of bright targets considered here. In particular the enhancement of the signal-to-noise ratio of the Fourier data, precipitated by the reduction in atmospheric noise, allows high fidelity imaging of complex sources with small numbers of short-exposure images relative to speckle. Multi-epoch measurements confirm the reliability of this imaging technique and our whole dataset provides a powerful demonstration of the capabilities of aperture masking methods when utilized with the current generation of large-aperture telescopes. The relationship between these new results and recent advances in interferometry and adaptive optics is briefly discussed.Comment: Accepted into Publications of the Astronomical Society of the Pacific. To appear in vol. 112. Paper contains 10 pages, 8 figure

Differential geometry with a projection: Application to double field theory

In recent development of double field theory, as for the description of the massless sector of closed strings, the spacetime dimension is formally doubled, i.e. from D to D+D, and the T-duality is realized manifestly as a global O(D,D) rotation. In this paper, we conceive a differential geometry characterized by a O(D,D) symmetric projection, as the underlying mathematical structure of double field theory. We introduce a differential operator compatible with the projection, which, contracted with the projection, can be covariantized and may replace the ordinary derivatives in the generalized Lie derivative that generates the gauge symmetry of double field theory. We construct various gauge covariant tensors which include a scalar and a tensor carrying two O(D,D) vector indices.Comment: 1+22 pages, No figure; a previous result on 4-index tensor removed, presentation improve