Spherically Symmetric Solutions in M\o ller's Tetrad Theory of Gravitation

The general solution of M\o ller's field equations in case of spherical symmetry is derived. The previously obtained solutions are verified as special cases of the general solution.Comment: LaTeX2e with AMS-LaTeX 1.2, 8 page

Elementary analysis of the special relativistic combination of velocities, Wigner rotation, and Thomas precession

The purpose of this paper is to provide an elementary introduction to the qualitative and quantitative results of velocity combination in special relativity, including the Wigner rotation and Thomas precession. We utilize only the most familiar tools of special relativity, in arguments presented at three differing levels: (1) utterly elementary, which will suit a first course in relativity; (2) intermediate, to suit a second course; and (3) advanced, to suit higher level students. We then give a summary of useful results, and suggest further reading in this often obscure field.Comment: V1: 25 pages, 6 figures; V2: 22 pages, 5 figures. The revised version is shortened and the arguments streamlined. Minor changes in notation and figures. This version matches the published versio

The effect of geometry on charge confinement in three dimensions

We show that, in contrast to the flat case, the Maxwell theory is not confining in the background of the three dimensional BTZ black-hole (covering space). We also study the effect of the curvature on screening behavior of Maxwell-Chern-Simons model in this space-time.Comment: 8 pages. To be published in Europhysics Letter

The Building the Bridge survey for z=3 Ly-alpha emitting galaxies I: method and first results

We present the first results of an observational programme at the ESO Very Large Telescope aimed at detecting a large sample of high-redshift galaxies fainter than the current spectroscopic limit of R=25.5 for Lyman-Break galaxies. In this paper, we describe the results of deep narrow and broad-band imaging and subsequent follow-up multi-object spectroscopy of faint high-redshift galaxies in the fields of the BRI1346-0322 and Q2138-4427. These QSOs have intervening absorbers, at redshifts z=2.85 and z=3.15 respectively, for which redshifted Ly-alpha emission falls within less than a few AA from the central wavelengths of existing VLT (~60 AA wide) narrow-band filters. We selected 37 and 27 candidate emission-line galaxies in the two fields respectively. About 85% of the candidates have R-band magnitudes fainter than R=25.5. The first spectroscopic follow-up of a sub-sample of the candidates resulted in 41 confirmed candidates and 4 foreground galaxies (three [OII] emitters and one CIV emitter). The confirmation rate is 82% and 68% in the field of BRI1346-0322 and Q2138-4427 respectively. In addition, we serendipitously detect a number of other emission-line sources on some of the slitlets not used for candidates. Of these, 9 are also most likely Ly-alpha emitters with redshifts ranging from 1.98 to 3.47. The redshift distribution of confirmed candidates in the field of BRI1346-0322 is consistent with being drawn from a uniform distribution weighted by the filter response curve, whereas the galaxies in the field of Q2138-4427 have redshifts clustering very close to the redshift of the damped Ly-alpha absorber. This latter fact indicates the existence of a large `pancake'-like structure confirming the earlier suggestions of Francis & Hewitt (1993).Comment: 12 pages, 10 figures, to appear in the Astronomy & Astrophysics main journal. A full resolution version of the paper can be found at : http://astro.ifa.au.dk/~jfynbo/papers/bridge.ps.g

The bigwig Project

We present the results of the -bigwig- project, which aims to design and implement a high-level domain-specific language for programming interactive Web services.The World Wide Web has undergone an extreme development since its invention ten years ago. A fundamental aspect is the change from static to dynamic generation of Web pages. Generating Web pages dynamically in dialogue with the client has the advantage of providing up-to-date and tailor-made information. The development of systems for constructing such dynamic Web services has emerged as a whole new research area. The language is designed by analyzing its application domain and identifying fundamental aspects of Web services. Each aspect is handled by a nearly independent sublanguage, and the entire collection is integrated into a common core language. The -bigwig- compiler uses the available Web technologies as target languages, making -bigwig- available on almost any combination of browser and server, without relying on plug-ins or server modules

The DSD Schema Language and its Applications

XML (eXtensible Markup Language), a linear syntax for trees, has gathered a remarkable amount of interest in industry. The acceptance of XML opens new venues for the application of formal methods such as specification of abstract syntax tree sets and tree transformations. A user domain may be specified as a set of trees. For example, XHTML is a user domain corresponding to the set of XML documents that make sense asHTML. A notation for defining such a set of XML trees is called a schema language. We believe that a useful schema notation must identify most of the syntacticrequirements that the documents in the user domain follow; allow efficient parsing; be readable to the user; allow a declarative default notation `a la CSS; and bemodular and extensible to support evolving classes of XML documents. In the present paper, we give a tutorial introduction to the DSD (Document Structure Description) notation as our bid on how to meet these requirements. TheDSD notation was inspired by industrial needs, and we show how DSDs help manage aspects of complex XML software through a case study about interactive voiceresponse systems (automated telephone answering systems, where input is through the telephone keypad or speech recognition). The expressiveness of DSDs goes beyond the DTD schema concept that is alreadypart of XML. We advocate the use of nonterminals in a top-down manner, coupled with boolean logic and regular expressions to describe how constraints on tree nodes depend on their context. We also support a general, declarative mechanism for inserting default elements and attributes that is reminiscent of CascadingStyle Sheets (CSS), a way of manipulating formatting instructions in HTML that is built into all modern browsers. Finally, we include a simple technique for evolving DSDs through selective redefinitions. DSDs are in many ways much more expressive than XML Schema (the schema language proposed by the W3C), but their syntactic and semantic definition in English is only 1/8th the size. Also, the DSD notation is self-describable: the syntax of legal DSD documents and all static semantic requirements can be captured in a DSD document, called the meta-DSD

The bigwig Project

We present the results of the <bigwig> project, which aims to design and implement a high-level domain-specific language for programming interactive Web services. A fundamental aspect of the development of the World Wide Web during the last decade is the gradual change from static to dynamic generation of Web pages. Generating Web pages dynamically in dialogue with the client has the advantage of providing up-to-date and tailor-made information. The development of systems for constructing such dynamic Web services has emerged as a whole new research area. The <bigwig> language is designed by analyzing its application domain and identifying fundamental aspects of Web services inspired by problems and solutions in existing Web service development languages. The core of the design consists of a session-centered service model together with a flexible template-based mechanism for dynamic Web page construction. Using specialized program analyses, certain Web specific properties are verified at compile-time, for instance that only valid HTML 4.01 is ever shown to the clients. In addition, the design provides high-level solutions to form field validation, caching of dynamic pages, and temporal-logic based concurrency control, and it proposes syntax macros for making highly domain-specific languages. The language is implemented via widely available Web technologies, such as Apache on the server-side and JavaScript and Java Applets on the client-side. We conclude with experience and evaluation of the project

Moving system with speeded-up evolution

In the classical (non-quantum) relativity theory the course of the moving clock is dilated as compared to the course of the clock at rest (the Einstein dilation). Any unstable system may be regarded as a clock. The time evolution (e.g., the decay) of a uniformly moving physical system is considered using the relativistic quantum theory. The example of a moving system is given whose evolution turns out to be speeded-up instead of being dilated. A discussion of this paradoxical result is presented.Comment: 10 pages, LaTe

On the Possibility of Measuring the Abraham Force using Whispering Gallery Modes

Critical experimental tests of the time-dependent Abraham force in phenomenological electrodynamics are scarce. In this paper we analyze the possibility of making use of intensity-modulated whispering gallery modes in a microresonator for this purpose. Systems of this kind appear attractive, as the strong concentration of electromagnetic fields near the rim of the resonator serves to enhance the Abraham torque exerted by the field. We analyze mainly spherical resonators, although as an introductory step we consider also the cylinder geometry. The order of magnitude of the Abraham torques are estimated by inserting reasonable values for the various input parameters. As expected, the predicted torques turn out to be very small, although probably not beyond any reach experimentally. Our main idea is essentially a generalization of the method used by G. B. Walker et al. [Can. J. Phys. 53, 2577] for low-frequency fields, to the optical case.Comment: 6 pages, no figures. Minor typos corrected, acknowledgment added. To appear in Phys. Rev.