Tensionless Strings and Supersymmetric Sigma Models: Aspects of the Target Space Geometry

In this thesis, two aspects of string theory are discussed, tensionless strings and supersymmetric sigma models. The equivalent to a massless particle in string theory is a tensionless string. Even almost 30 years after it was first mentioned, it is still quite poorly understood. We discuss how tensionless strings give rise to exact solutions to supergravity and solve closed tensionless string theory in the ten dimensional maximally supersymmetric plane wave background, a contraction of AdS(5)xS(5) where tensionless strings are of great interest due to their proposed relation to higher spin gauge theory via the AdS/CFT correspondence. For a sigma model, the amount of supersymmetry on its worldsheet restricts the geometry of the target space. For N=(2,2) supersymmetry, for example, the target space has to be bi-hermitian. Recently, with generalized complex geometry, a new mathematical framework was developed that is especially suited to discuss the target space geometry of sigma models in a Hamiltonian formulation. Bi-hermitian geometry is so-called generalized Kaehler geometry but the relation is involved. We discuss various amounts of supersymmetry in phase space and show that this relation can be established by considering the equivalence between the Hamilton and Lagrange formulation of the sigma model. In the study of generalized supersymmetric sigma models, we find objects that favor a geometrical interpretation beyond generalized complex geometry.Comment: 87 Pages, PhD Thesi

Realization and application of a 111 million pixel backside-illuminated detector and camera

A full-wafer, 10,580 $\times$ 10,560 pixel (95 $\times$ 95 mm) CCD was designed and tested at Semiconductor Technology Associates (STA) with 9 um square pixels and 16 outputs. The chip was successfully fabricated in 2006 at DALSA and some performance results are presented here. This program was funded by the Office of Naval Research through a Small Business Innovation in Research (SBIR) program requested by the U.S. Naval Observatory for its next generation astrometric sky survey programs. Using Leach electronics, low read-noise output of the 111 million pixels requires 16 seconds at 0.9 MHz. Alternative electronics developed at STA allow readout at 20 MHz. Some modifications of the design to include anti-blooming features, a larger number of outputs, and use of p-channel material for space applications are discussed.Comment: 8 pages, 5 figures, accepted for SPIE conference 669

Preliminary design of a geologic sample acquisition and transport device Final report, May - Oct. 1965

Design concept for breadboard model of geological sample and transport device for Surveyor projec

Boundary States and Symplectic Fermions

We investigate the set of boundary states in the symplectic fermion description of the logarithmic conformal field theory with central charge c=-2. We show that the thus constructed states correspond exactly to those derived under the restrictions of the maximal chiral symmetry algebra for this model, W(2,3,3,3). This connects our previous work to the coherent state approach of Kawai and Wheater.Comment: LaTeX file, 1+11 pages, minor change

Generalized Hyperkaehler Geometry and Supersymmetry

We propose the definition of (twisted) generalized hyperkaehler geometry and its relation to supersymmetric non-linear sigma models. We also construct the corresponding twistor space.Comment: 15 page

Rats in Bliss: A Minimal-Deviation Model of Ratio Schedule Performance

The minimum-deviation theory predicts that an organism will seek to minimize the behavioral distance between an unconstrained baseline and constrained conditions caused by reinforcement schedules (Staddon, 1979). According to the performance model proposed by Allison (1983), behavior under scheduled constraint will come as close as possible to an unconstrained bliss point or behavioral ideal. The present study examined applications of these models to fixed ratio (FR) schedules. Six rats were first exposed to a paired baseline procedure to establish their individual bliss points. Each rat was then exposed to a series of two fixed ratio schedules: FR 2 and FR 10. The model failed to predict the response rates; rats pressed a bar consistently more often than predicted by the model. These results are consistent with an earlier study in our lab by Witte (1994), which failed to support the model on interval schedules. The results have implications for minimum-distance models of learning and performance

Alaska's Water: A Critical Resource

Proceeding

T-duality and Generalized Complex Geometry

We find the explicit T-duality transformation in the phase space formulation of the N=(1,1) sigma model. We also show that the T-duality transformation is a symplectomorphism and it is an element of O(d,d). Further, we find the explicit T-duality transformation of a generalized complex structure in this model. We also show that the extended supersymmetry of the sigma model is preserved under the T-duality.Comment: 18 pages; added references; published versio

Natürlich ist Mehrsprachigkeit toll! Aber was hat das mit meinem Unterricht zu tun?

In den vergangenen Jahren sind mehrere Konzepte und Ansätze für das Unterrichten sprachlicher Fächer entwickelt worden, die unter den Begriff Mehrsprachigkeitsdidaktik fallen. Sie zielen auf den Aufbau einer integrativen Mehrsprachigkeit bei den Lernenden, indem mehrsprachige Kompetenzen und Sprachlernerfahrungen in den Sprachunterricht einbezogen werden. In diesem Artikel werden Ergebnisse eines narrativen Reviews zwölf empirischer Studien vorgestellt, die den Fragen nachgehen, wie Sprachlehrkräfte im deutschsprachigen Raum zu Mehrsprachigkeitsdidaktik stehen, wie sie solche Konzepte im Unterricht umsetzen und welche Unterstützung sie dabei erhalten. Auf der Grundlage der Ergebnisse werden Empfehlungen für die Aus- und Fortbildung von Sprachlehrkräften, Lehr- und Lernmaterialien, weiterführende Forschung sowie die Unterrichtspraxis formuliert

80-Channel Multiplexer-Demultiplexer Module for DWDM Communications using Hybrid AWG -- Interleaver Technology

Aside from the more traditional data, voice and e-mail communications, new bandwidth intensive applications in the larger consumer markets, such as music, digital pictures and movies, have led to an explosive increase in the demand for transmission capacity for optical communications networks. This has resulted in a widespread deployment of Dense Wavelength Division Multiplexing (DWDM) as a means of increasing the communications capacity by multiplexing and transmitting signals of different wavelengths (establishing multiple communication channels) through a single strand of fiber. We report on the design, assembly and characterization of a 50-GHz, 80-channel Mux-Demux module for DWDM systems. The module has been assembled from two commercially available 100 GHz, 40-channel Array Waveguide Grating (AWG) modules and a 50-GHz to 100-GHz interleaver. Relevant performance parameters such as insertion loss, channel uniformity, next-channel isolation (crosstalk) and integrated cross-talk are presented and discussed in contrast with the performance of other competing technologies such as Thin-Film-Filter-based Mux-Demux devices