754 research outputs found
Self-Dual Tensors and Partial Supersymmetry Breaking in Five Dimensions
We study spontaneous supersymmetry breaking of five-dimensional supergravity
theories from sixteen to eight supercharges in Minkowski vacua. This N=4 to N=2
breaking is induced by Abelian gaugings that require the introduction of
self-dual tensor fields accompanying the vectors in the gravity multiplet and
vector multiplets. These tensor fields have first-order kinetic terms and can
become massive by a Stueckelberg-like mechanism. We identify the general class
of N=2 vacua and show how the N=4 spectrum splits into massless and massive N=2
multiplets. In particular, we find a massive gravitino multiplet, containing
two complex massive tensors, and a number of massive tensor multiplets and
hypermultiplets. We determine the resulting N=2 effective action for the
massless multiplets obtained by integrating out massive fields. We show that
the metric and Chern-Simons terms of the vectors are corrected at one-loop by
massive tensors as well as spin-1/2 and spin-3/2 fermions. These contributions
are independent of the supersymmetry-breaking scale and thus have to be
included at arbitrarily low energies.Comment: 33 page
The Arithmetic of Elliptic Fibrations in Gauge Theories on a Circle
The geometry of elliptic fibrations translates to the physics of gauge
theories in F-theory. We systematically develop the dictionary between
arithmetic structures on elliptic curves as well as desingularized elliptic
fibrations and symmetries of gauge theories on a circle. We show that the
Mordell-Weil group law matches integral large gauge transformations around the
circle in Abelian gauge theories and explain the significance of Mordell-Weil
torsion in this context. We also use Higgs transitions and circle large gauge
transformations to introduce a group law for genus-one fibrations with
multi-sections. Finally, we introduce a novel arithmetic structure on elliptic
fibrations with non-Abelian gauge groups in F-theory. It is defined on the set
of exceptional divisors resolving the singularities and divisor classes of
sections of the fibration. This group structure can be matched with certain
integral non-Abelian large gauge transformations around the circle when
studying the theory on the lower-dimensional Coulomb branch. Its existence is
required by consistency with Higgs transitions from the non-Abelian theory to
its Abelian phases in which it becomes the Mordell-Weil group. This hints
towards the existence of a new underlying geometric symmetry.Comment: 43 pages, 3 figure
Partial Supergravity Breaking and the Effective Action of Consistent Truncations
We study vacua of N = 4 half-maximal gauged supergravity in five dimensions
and determine crucial properties of the effective theory around the vacuum. The
main focus is on configurations with exactly two broken supersymmetries, since
they frequently appear in consistent truncations of string theory and
supergravity. Evaluating one-loop corrections to the Chern-Simons terms we find
necessary conditions to ensure that a consistent truncation also gives rise to
a proper effective action of an underlying more fundamental theory. To obtain
concrete examples, we determine the N=4 action of M-theory on six-dimensional
SU(2)-structure manifolds with background fluxes. Calabi-Yau threefolds with
vanishing Euler number are examples of SU(2)-structure manifolds that yield N=2
Minkowski vacua. We find that that one-loop corrections to the Chern-Simons
terms vanish trivially and thus do not impose constraints on identifying
effective theories. This result is traced back to the absence of isometries on
these geometries. Examples with isometries arise from type IIB supergravity on
squashed Sasaki-Einstein manifolds. In this case the one-loop gauge
Chern-Simons terms vanish due to non-trivial cancellations, while the one-loop
gravitational Chern-Simons terms are non-zero.Comment: 44 pages, v2: minor changes, references adde
Entwicklung stationärer Phasen für die Ionenchromatographie zur Trennung von Kohlenhydraten
Diese Arbeit umfasst die Herstellung und Charakterisierung von neuen stationären Phasen zur Trennung von Kohlenhydraten mittels Anionenchromatographie und elektrochemischer Detektion. Auf hochquervernetzten PS-DVB-Harzen konnten durch Chloromethylierung, Beschichtung und pfropfpolymerisation unterschiedliche Typen von Oberflächenmodifizierungen durchgeführt werden, die zu präfunktionalisierten Trägermaterialien führten. Die anschließende Funktionalisierung mit verschiedenen Aminen und Diaminen führte zu stabilen Anionenaustauschern hoher Kapazität und Trennleistung und konnten erfolgreich zur Trennung von Kohlenhydraten eingesetzt werden. Auf dem Gebiet der agglomerierten Ionenaustauscher wurde das bewährte Konzept der Latexaustauscher weiterentwickelt und durch die Immobilisierung von polykationischen Ketten in Form von Ionenen erweitert. Die Struktur der Ionene ist durch eine Vielzahl an verfügbarenMonomeren sehr variabel und die erhaltenen Ionenaustauscher zur Trennung von Kohlenhydraten geeignet. Trends und Trenneigenschaften aller hergestellten Phasen wurden untersucht und unter dem Aspekt der Eignung zur Trennung von Kohlenhydraten untereinander verglichen
Optimal non-circular fiber geometries for image scrambling in high-resolution spectrographs
Optical fibers are a key component for high-resolution spectrographs to
attain high precision in radial velocity measurements. We present a custom
fiber with a novel core geometry - a 'D'-shape. From a theoretical standpoint,
such a fiber should provide superior scrambling and modal noise mitigation,
since unlike the commonly used circular and polygonal fiber cross sections, it
shows chaotic scrambling. We report on the fabrication process of a test fiber
and compare the optical properties, scrambling performance, and modal noise
behavior of the D-fiber with those of common polygonal fibers.Comment: 7 pages, 6 figures, submitted to SPIE Astronomical Telescopes &
Instrumentation 2016 (9912-192
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