Bosonization as Duality

We show that bosonization in two dimensions can be derived as a special case of the duality transformations that have recently been used to good effect in string theory. This allows the construction of the bosonic counterpart of any fermionic theory simply by `following your nose' using the standard duality transformation rules. We work through the bosonization of the Dirac fermion, the massive and massless Thirring models, and a fermion on a cylindrical spacetime as illustrative examples.Comment: plain TeX, 21 page

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

Integration of the atmospheric fluctuations in a dual-field optical interferometer: the short exposure regime

Spatial phase-referencing in dual-field optical interferometry is reconsidered. Our analysis is based on the 2-sample variance of the differential phase between target and reference star. We show that averaging over time of the atmospheric effects depends on this 2-sample phase variance (Allan variance) rather than on the true variance. The proper expression for fringe smearing beyond the isoplanatic angle is derived. With simulations of atmospheric effects, based on a Paranal turbulence model, we show how the performances of a dual-field optical interferometer can be evaluated in a diagram 'separation angle' versus 'magnitude of faint object'. In this diagram, a domain with short exposure is found to be most useful for interferometry, with about the same magnitude limits in the H and K bands. With star counts from a Galaxy model, we evaluate the sky coverage for differential astrometry and detection of exoplanets, i.e. likelihood of faint reference stars in the vicinity of a bright target. With the 2mass survey, we evaluate sky coverage for phase-referencing, i.e. avaibility of a bright enough star for main delay tracking in the vicinity of any target direction.Comment: 9 pages, 8 figures, accepted for publication in A&

Unifying gauge couplings at the string scale

Using the current precision electroweak data, we look for the minimal particle content which is necessary to add to the standard model in order to have a complete unification of gauge couplings and gravity at the weakly coupled heterotic string scale. We find that the addition of a vector-like fermion at an intermediate scale and a non-standard hypercharge normalization are in general sufficient to achieve this goal at two-loop level. Requiring the extra matter scale to be below the TeV scale, it is found that the addition of three vector-like fermion doublets with a mass around 700 GeV yields a perfect string-scale unification, provided that the affine levels are $(k_Y, k_2 ,k_3)=(13/3, 1, 2)$, as in the $SU(5) \times SU(5)$ string-GUT. Furthermore, if supersymmetry is broken at the unification scale, the Higgs mass is predicted in the range 125 GeV - 170 GeV, depending on the precise values of the top quark mass and $\tan \beta$ parameter.Comment: 11 pages, 4 eps figures, using jpconf style, talk given at CORFU2005, RTN meeting ``The Quest for Unification: Theory Confronts Experiment'', 11 - 18 September 2005, Corfu, Greec

Empirical macromodels under test: a comparative simulation study of the employment effects of a revenue neutral cut in social security contributions

In the paper we simulate a revenue-neutral cut in the social security contribution rate using five different types of macro- / microeconomic models, namely two models based on time-series data where the labour market is modelled basically demand oriented, two models of the class of computable equilibrium models which are supply oriented and finally a firm specific model for international tax burden comparisons. Our primary interest is in the employment effects the models predict due to the cut in the contribution rate. It turns out that qualitatively all models considered predict an increase in employment three years after the cut. But the employment effects differ considerably in magnitude, which follows immediately from the different behavioral assumptions underlying the different models. -- In dem Beitrag wird der Beschäftigungseffekt infolge einer aufkommensneutralen Senkung der Sozialversicherungsbeiträge simuliert. Zu diesem Zweck werden fünf unterschiedliche ökonomische Modelle verwendet, namentlich zwei Modelle, die auf Zeitreihendaten aufbauen und in denen der Arbeitsmarkt überwiegend von der Nachfrageseite dominiert wird, zwei Modelle aus der Klasse der computable equilibrium models, die typischerweise angebotsorientiert sind, und ein mikroökonomisches, firmenspezifisches Steuerbelastungsvergleichsmodell. Alle Simulationsergebnisse der Modelle weisen auf einen, wenngleich teilweise kleinen, positiven Beschäftigungseffekt hin, der sich allerdings beträchtlich in seiner Größenordnung unterscheidet. Dies ist eine unmittelbare Folge aus den unterschiedlichen Verhaltensannahmen, die den einzelnen Modellen unterliegen.

Fringe tracking and spatial filtering: phase jumps and dropouts

Fringe tracking in interferometers is typically analyzed with the implicit assumption that there is a single phase associated with each telescope in the array. If the telescopes have apertures significantly larger than r0 and only partial adaptive optics correction, then the phase measured by a fringe sensor may differ significantly from the "piston" component of the aperture phase. In some cases, speckle noise will cause "branch points" in the measured phase as a function of time, causing large and sudden jumps in the phase. We present simulations showing these effects in order to understand their implications for the design of fringe tracking algorithms.Comment: 9 pages, to be published in Proc. SPIE conference 7013 "Optical and Infrared Interferometry", Schoeller, Danchi, and Delplancke (eds.

Supersymmetry and Stationary Solutions in Dilaton-Axion Gravity

New stationary solutions of $4$-dimensional dilaton-axion gravity are presented, which correspond to the charged Taub-NUT and Israel-Wilson-Perjes (IWP) solutions of Einstein-Maxwell theory. The charged axion-dilaton Taub-NUT solutions are shown to have a number of interesting properties: i) manifest $SL(2,R)$ symmetry, ii) an infinite throat in an extremal limit, iii) the throat limit coincides with an exact CFT construction. The IWP solutions are shown to admit supersymmetric Killing spinors, when embedded in $d=4,N=4$ supergravity. This poses a problem for the interpretation of supersymmetric rotating solutions as physical ground states. In the context of $10$-dimensional geometry, we show that dimensionally lifted versions of the IWP solutions are dual to certain gravitational waves in string theory.Comment: 23 pages (latex), SU-ITP-94-12, UMHEP-407, QMW-PH-94-1

An architecture for using commodity devices and smart phones in health systems

The potential of patient-centred care and a connected eHealth ecosystem can be developed through socially responsible innovative architectures. The purpose of this paper is to define key innovation needs. This is achieved through conceptual development of an architecture for common information spaces with emergent end-user applications by supporting intelligent processing of measurements, data and services at the Internet of Things (IoT) integration level. The scope is conceptual definition, and results include descriptions of social, legal and ethical requirements, an architecture, services and connectivity infrastructures for consumer-oriented healthcare systems linking co-existing healthcare systems and consumer devices. We conclude with recommendations based on an analysis of research challenges related to how to process the data securely and anonymously and how to interconnect participants and services with different standards and interaction protocols, and devices with heterogeneous hardware and software configurations

T-Duality in 2-D Integrable Models

The non-conformal analog of abelian T-duality transformations relating pairs of axial and vector integrable models from the non abelian affine Toda family is constructed and studied in detail.Comment: 14 pages, Latex, v.2 misprints corrected, reference added, to appear in J. Phys.