Supertubes and Supercurves from M-Ribbons

We construct 1/4 BPS configurations, `M-ribbons', in M-theory on T^2, which give the supertubes and supercurves in type IIA theory upon dimensional reduction. These M-ribbons are generalized so as to be consistent with the SL(2,Z) modular transformation on T^2. In terms of the type IIB theory, the generalized M-ribbons are interpreted as an SL(2,Z) duality family of super D-helix. It is also shown that the BPS M-ribbons must be straight in one direction.Comment: 10 pages, 1 figure, references added, footnote added, BPS eq. (36) is examined without using the solution of field equations, some expressions are improve

Phase Moduli Space of Supertubes

We study possible deformations of BPS supertubes keeping their conserved charges fixed. We show that there is no flat direction to closed supertubes of circular cross section with uniform electric and magnetic fields, and also to open planar supertubes. We also find that there are continuously infinite flat deformations to supertubes of general shape under certain conditions.Comment: 12 pages, reference adde

Field Theory Supertubes

Starting with intersecting M2-branes in M-theory, the IIA supertube can be found by compactification with a boost to the speed of light in the compact dimension. A similar procedure applied to Donaldson-Uhlenbeck-Yau instantons on \bC^3, viewed as intersecting membranes of 7D supersymmetric Yang-Mills (SYM) theory, yields (for finite boost) a new set of 1/4 BPS equations for 6D SYM-Higgs theory, and (for infinite boost) a generalization of the dyonic instanton equations of 5D SYM-Higgs theory, solutions of which are interpreted as Yang-Mills supertubes and realized as configurations of IIB string theory.Comment: 11 pages. Contribution to Strings '04. Revised to include minor corrections and additional reference

Mixed phase and bound states in the phase diagram of the extended Hubbard model

The paper examines part of the ground state diagram of the extended Hubbard model, with the on-site attraction U0 in the presence of charge density waves, superconducting and $\eta$-superconducting order parameters. We show the possibility of the stabilization of the mixed state, with all three nonzero order parameters, in the model with nearest neighbor interactions. The other result of the paper is application of the exact solution of the Schrodinger equation for the two electron bound state, as an additional bound for the phase diagram of the model, resulting in the partial suppression of the superconducting state of the s-wave symmetry, in favor of the normal state phase.Comment: submitted to Acta Physica Polonica

Decreta Regni Mediaevalis hungariae - The Laws of Medieval Hungary IV. és VI. kötet = Decreta Regni Mediaevalis hungariae - The Laws of Medieval Hungary Vols. IV. és VI.

Röviden: a DRMH IV kötetéhez (Jagellókori törvények) szükséges kutatást (latin szöveg, fordítás, jegyzetelés) befejeztük. A kézirat, bevezetö tanulmánnyal, névmutatókkal, stb. 2009 öszére elkészül és 2010 elején nyomdába mehet. A VI Kötet egy általános glosszárium és index lett volna. Eheleyett egy az I-V kötetre vonatkozó glosszárium a IV kötethez csatolva fog megjelenni. Hagyományos index (index rerum et verborum) elkészítésétöl eltekintetünk, mert munkában van egy a teljes ötkötetes sorozatot tartalmazandó digitális kiadás, amelyben majd minden szóra stb. keresni lehet. | In brief: research for vol. 4 of DRMH (decreta of the Jagiellonian age) has been completed as planned: Latin original edited, translation, annotations written. Final copy, including introductory study, indices etc. will be ready by Fall '09 and the volume will go to press in early 2010. Vol. 6 was planned to be a general glossary and indices. We decided to publish a general glossary for vols. 1-5 attached to vol. 4, while we forego the publication of a traditional index (of word, subjects etc.), considering that a digital edition of the five volumes is inpreparation. That will allow free browsing for any word or concept

Playing with sandpiles

The Bak-Tang-Wiesenfeld sandpile model provdes a simple and elegant system with which to demonstate self-organized criticality. This model has rather remarkable mathematical properties first elucidated by Dhar. I demonstrate some of these properties graphically with a simple computer simulation.Comment: Contribution to the Niels Bohr Summer Institute on Complexity and Criticality; to appear in a Per Bak Memorial Issue of PHYSICA A; 6 pages 3 figure

Price Variations in a Stock Market With Many Agents

Large variations in stock prices happen with sufficient frequency to raise doubts about existing models, which all fail to account for non-Gaussian statistics. We construct simple models of a stock market, and argue that the large variations may be due to a crowd effect, where agents imitate each other's behavior. The variations over different time scales can be related to each other in a systematic way, similar to the Levy stable distribution proposed by Mandelbrot to describe real market indices. In the simplest, least realistic case, exact results for the statistics of the variations are derived by mapping onto a model of diffusing and annihilating particles, which has been solved by quantum field theory methods. When the agents imitate each other and respond to recent market volatility, different scaling behavior is obtained. In this case the statistics of price variations is consistent with empirical observations. The interplay between ``rational'' traders whose behavior is derived from fundamental analysis of the stock, including dividends, and ``noise traders'', whose behavior is governed solely by studying the market dynamics, is investigated. When the relative number of rational traders is small, ``bubbles'' often occur, where the market price moves outside the range justified by fundamental market analysis. When the number of rational traders is larger, the market price is generally locked within the price range they define.Comment: 39 pages (Latex) + 20 Figures and missing Figure 1 (sorry), submitted to J. Math. Eco

Grand Illusions: Large-Scale Optical Toys and Contemporary Scientific Spectacle

Nineteenth-century optical toys that showcase illusions of motion such as the phenakistoscope, zoetrope, and praxinoscope, have enjoyed active “afterlives” in the twentieth and twenty-first centuries. Contemporary incarnations of the zoetrope are frequently found in the realms of fine art and advertising, and they are often much larger than their nineteenth-century counterparts. This article argues that modern-day optical toys are able to conjure feelings of wonder and spectacle equivalent to their nineteenth-century antecedents because of their adjustment in scale. Exploring a range of contemporary philosophical toys found in arts, entertainment, and advertising contexts, the article discusses various technical adjustments made to successfully “scale up” optical toys, including the replacement of hand-spun mechanisms with larger sources of motion and the use of various means such as architectural features and stroboscopic lights to replace traditional shutter mechanisms such as the zoetrope’s dark slots. Critical consideration of scale as a central feature of these installations reconfigures the relationship between audience and device. Large-scale adaptations of optical toys revise the traditional conception of the user, who is able to tactilely manipulate and interact with the apparatus, instead positing a viewer who has less control over the illusion’s operation and is instead a captive audience surrounded by the animation. It is primarily through their adaptation of scale that contemporary zoetropes successfully elicit wonder as scientific spectacles from their audiences today