2,313 research outputs found
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 . 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 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
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