Vacuum field energy and spontaneous emission in anomalously dispersive cavities

Anomalously dispersive cavities, particularly white light cavities, may have larger bandwidth to finesse ratios than their normally dispersive counterparts. Partly for this reason, their use has been proposed for use in LIGO-like gravity wave detectors and in ring-laser gyroscopes. In this paper we analyze the quantum noise associated with anomalously dispersive cavity modes. The vacuum field energy associated with a particular cavity mode is proportional to the cavity-averaged group velocity of that mode. For anomalously dispersive cavities with group index values between 1 and 0, this means that the total vacuum field energy associated with a particular cavity mode must exceed $\hbar \omega/2$. For white light cavities in particular, the group index approaches zero and the vacuum field energy of a particular spatial mode may be significantly enhanced. We predict enhanced spontaneous emission rates into anomalously dispersive cavity modes and broadened laser linewidths when the linewidth of intracavity emitters is broader than the cavity linewidth.Comment: 9 pages, 4 figure

Evaluierung des Rechtsextremismus-Datei-Gesetzes nach Artikel 3 Absatz 2 des Gesetzes zur Verbesserung der Bekämpfung des Rechtsextremismus

Artikel 3 Absatz 2 des Gesetzes zur Verbesserung der Bekämpfung des Rechtsextremismus vom 20. August 2012 sieht eine Evaluierung des RED-G vor dem 31. Januar 2016 unter Einbeziehung wissenschaftlicher Sachverständiger vor. Mit der Durchführung der Evaluation hat das Bundesministerium des Innern (BMI) im Einvernehmen mit dem Deutschen Bundestag das Institut für Gesetzesfolgenabschätzung und Evaluation beauftragt. Das Evaluationsvorhaben verfolgt zum einen das Ziel, die Häufigkeit und die Auswirkungen der mit den Datenerhebungen, -verarbeitungen und -nutzungen verbundenen Grundrechtseingriffe im Rahmen der RED zu erfassen. Zum anderen geht es um die Untersuchung der Wirksamkeit der gesetzlichen Regelungen im Hinblick auf die Bekämpfung des gewaltbezogenen Rechtsextremismus. Hierzu wird u.a. untersucht, welche Veränderungen sich beim Informationsaustausch zwischen den Sicherheitsbehörden durch die Nutzung der RED ergeben haben, inwieweit die Regelungen des RED-G praktikabel sind und wie sich die technisch-organisatorischen Voraussetzungen für die Nutzung der RED darstellen. Die Evaluation verfolgt dabei einen interdisziplinären Ansatz, der aus einer Verknüpfung einer empirisch-sozialwissenschaftlichen mit einer rechtswissenschaftlichen Analyse besteht

The Impact of Accents on Automatic Recognition of South African English Speech: A Preliminary Investigation

The accent with which words are spoken can have a strong effect on the performance of a speech recognition system. In a multilingual country such as South Africa where English is not the first language of most citizens, the need to address this issue is critical when building speech-based systems. In this project we trained two sets of hidden Markov Models for isolated word English speech. The first set of models was trained with native English speakers and the second set was trained with non-native speakers from a representative sample of major South African accent groups. We compared the recognition accuracies of the two sets of models and found that the models trained with accented English performed better. This preliminary research indicates that there is merit to committing resources to the task of accented training

Mapping 6D N = 1 supergravities to F-theory

We develop a systematic framework for realizing general anomaly-free chiral 6D supergravity theories in F-theory. We focus on 6D (1, 0) models with one tensor multiplet whose gauge group is a product of simple factors (modulo a finite abelian group) with matter in arbitrary representations. Such theories can be decomposed into blocks associated with the simple factors in the gauge group; each block depends only on the group factor and the matter charged under it. All 6D chiral supergravity models can be constructed by gluing such blocks together in accordance with constraints from anomalies. Associating a geometric structure to each block gives a dictionary for translating a supergravity model into a set of topological data for an F-theory construction. We construct the dictionary of F-theory divisors explicitly for some simple gauge group factors and associated matter representations. Using these building blocks we analyze a variety of models. We identify some 6D supergravity models which do not map to integral F-theory divisors, possibly indicating quantum inconsistency of these 6D theories.Comment: 37 pages, no figures; v2: references added, minor typos corrected; v3: minor corrections to DOF counting in section

Verdeckte Datenerhebungsmassnahmen in der polizeilichen Praxis

Am 26. Januar 2011 hat der rheinland-pfälzische Landtag eine Novelle des Polizei- und Ordnungsbe-hördengesetzes (POG) beschlossen. Ziel des Änderungsgesetzes ist die Schaffung eines modernen und effizienten POG, um die Sicherheit der Bürgerinnen und Bürger weiterhin gewährleisten zu kön-nen. § 100 POG enthält eine erneute Evaluationsverpflichtung, die vorsieht, dass die Landesregierung dem Landtag über die Wirksamkeit bestimmter eingriffsintensiver Maßnahmen berichtet. Hierzu gehören • die Datenerhebung durch den verdeckten Einsatz technischer Mittel in oder aus Wohnungen, • die Datenerhebung durch den Einsatz technischer Mittel zur Überwachung und Aufzeichnung der Telekommunikation, • Auskunft über die Telekommunikation, • Auskunft über Nutzungsdaten, • Datenerhebung durch den Einsatz technischer Mittel in informationstechnischen Systemen, • Funkzellenabfrage, • besondere Formen des Datenabgleichs. Das Institut für Gesetzesfolgenabschätzung und Evaluation wurde vom rheinland-pfälzischen Minis-terium des Innern, für Sport und Infrastruktur mit der Durchführung der Evaluation beauftragt

Deformed Quantum Cohomology and (0,2) Mirror Symmetry

We compute instanton corrections to correlators in the genus-zero topological subsector of a (0,2) supersymmetric gauged linear sigma model with target space P1xP1, whose left-moving fermions couple to a deformation of the tangent bundle. We then deduce the theory's chiral ring from these correlators, which reduces in the limit of zero deformation to the (2,2) ring. Finally, we compare our results with the computations carried out by Adams et al.[ABS04] and Katz and Sharpe[KS06]. We find immediate agreement with the latter and an interesting puzzle in completely matching the chiral ring of the former.Comment: AMSLatex, 30 pages, one eps figure. V4: typos corrected, final version appearing in JHE

U(n) Spectral Covers from Decomposition

We construct decomposed spectral covers for bundles on elliptically fibered Calabi-Yau threefolds whose structure groups are S(U(1) x U(4)), S(U(2) x U(3)) and S(U(1) x U(1) x U(3)) in heterotic string compactifications. The decomposition requires not only the tuning of the SU(5) spectral covers but also the tuning of the complex structure moduli of the Calabi-Yau threefolds. This configuration is translated to geometric data on F-theory side. We find that the monodromy locus for two-cycles in K3 fibered Calabi-Yau fourfolds in a stable degeneration limit is globally factorized with squared factors under the decomposition conditions. This signals that the monodromy group is reduced and there is a U(1) symmetry in a low energy effective field theory. To support that, we explicitly check the reduction of a monodromy group in an appreciable region of the moduli space for an $E_6$ gauge theory with (1+2) decomposition. This may provide a systematic way for constructing F-theory models with U(1) symmetries.Comment: 41 pages, 14 figures; v2: minor improvements and a reference adde

Seiberg-Witten prepotential for E-string theory and global symmetries

We obtain Nekrasov-type expressions for the Seiberg-Witten prepotential for the six-dimensional (1,0) supersymmetric E-string theory compactified on T^2 with nontrivial Wilson lines. We consider compactification with four general Wilson line parameters, which partially break the E_8 global symmetry. In particular, we investigate in detail the cases where the Lie algebra of the unbroken global symmetry is E_n + A_{8-n} with n=8,7,6,5 or D_8. All our Nekrasov-type expressions can be viewed as special cases of the elliptic analogue of the Nekrasov partition function for the SU(N) gauge theory with N_f=2N flavors. We also present a new expression for the Seiberg-Witten curve for the E-string theory with four Wilson line parameters, clarifying the connection between the E-string theory and the SU(2) Seiberg-Witten theory with N_f=4 flavors.Comment: 22 pages. v2: comments and a reference added, version to appear in JHE

Gauge Fluxes in F-theory and Type IIB Orientifolds

We provide a detailed correspondence between G_4 gauge fluxes in F-theory compactifications with SU(n) and SU(n)x(1) gauge symmetry and their Type IIB orientifold limit. Based on the resolution of the relevant F-theory Tate models we classify the factorisable G_4-fluxes and match them with the set of universal D5-tadpole free U(1)-fluxes in Type IIB. Where available, the global version of the universal spectral cover flux corresponds to Type IIB gauge flux associated with a massive diagonal U(1). In U(1)-restricted Tate models extra massless abelian fluxes exist which are associated with specific linear combinations of Type IIB fluxes. Key to a quantitative match between F-theory and Type IIB is a proper treatment of the conifold singularity encountered in the Sen limit of generic F-theory models. We also shed further light on the brane recombination process relating generic and U(1)-restricted Tate models.Comment: 53 pages, 3 figures; v2: Refs added; v3: minor corrections to match version published in JHE

Tate Form and Weak Coupling Limits in F-theory

We consider the weak coupling limit of F-theory in the presence of non-Abelian gauge groups implemented using the traditional ansatz coming from Tate's algorithm. We classify the types of singularities that could appear in the weak coupling limit and explain their resolution. In particular, the weak coupling limit of SU(n) gauge groups leads to an orientifold theory which suffers from conifold singulaties that do not admit a crepant resolution compatible with the orientifold involution. We present a simple resolution to this problem by introducing a new weak coupling regime that admits singularities compatible with both a crepant resolution and an orientifold symmetry. We also comment on possible applications of the new limit to model building. We finally discuss other unexpected phenomena as for example the existence of several non-equivalent directions to flow from strong to weak coupling leading to different gauge groups.Comment: 34 page