138 research outputs found
Boundary Correlators in Supergroup WZNW Models
We investigate correlation functions for maximally symmetric boundary
conditions in the WZNW model on GL(1|1). Special attention is payed to volume
filling branes. Generalizing earlier ideas for the bulk sector, we set up a
Kac-Wakimoto-like formalism for the boundary model. This first order formalism
is then used to calculate bulk-boundary 2-point functions and the boundary
3-point functions of the model. The note ends with a few comments on
correlation functions of atypical fields, point-like branes and generalizations
to other supergroups.Comment: 33 page
Asymmetric Cosets
The aim of this work is to present a general theory of coset models G/H in
which different left and right actions of H on G are gauged. Our main results
include a formula for their modular invariant partition function, the
construction of a large set of boundary states and a general description of the
corresponding brane geometries. The paper concludes with some explicit
applications to the base of the conifold and to the time-dependent Nappi-Witten
background.Comment: 34 pages, LaTeX, 8 figures, 1 table, v2: references added, v3: typos
correcte
Semiclassical quantization of the hydrogen atom in crossed electric and magnetic fields
The S-matrix theory formulation of closed-orbit theory recently proposed by
Granger and Greene is extended to atoms in crossed electric and magnetic
fields. We then present a semiclassical quantization of the hydrogen atom in
crossed fields, which succeeds in resolving individual lines in the spectrum,
but is restricted to the strongest lines of each n-manifold. By means of a
detailed semiclassical analysis of the quantum spectrum, we demonstrate that it
is the abundance of bifurcations of closed orbits that precludes the resolution
of finer details. They necessitate the inclusion of uniform semiclassical
approximations into the quantization process. Uniform approximations for the
generic types of closed-orbit bifurcation are derived, and a general method for
including them in a high-resolution semiclassical quantization is devised
Representation theory of sl(2|1)
In this note we present a complete analysis of finite dimensional
representations of the Lie superalgebra sl(2|1). This includes, in particular,
the decomposition of all tensor products into their indecomposable building
blocks. Our derivation makes use of a close relation with the representation
theory of gl(1|1) for which analogous results are described and derived.Comment: 26pp, v2: minor typos correcte
Supersymmetric Polarization Anomaly in Photonic Discrete-Time Quantum Walks
Quantum anomalies lead to finite expectation values that defy the apparent symmetries of a system. These anomalies are at the heart of topological effects in electronic, photonic, and atomic systems, where they result in a unique response to external fields but generally escape a more direct observation. Here, we implement an optical-network realization of a discrete-time quantum walk, where such an anomaly can be observed directly in the unique circular polarization of a topological midgap state. We base the system on a single-step protocol overcoming the experimental infeasibility of earlier multistep protocols. The evolution combines a chiral symmetry with a previously unexplored unitary version of supersymmetry. Having experimental access to the position and the coin state of the walker, we perform a full polarization tomography and provide evidence for the predicted anomaly of the midgap states. This approach opens the prospect to dynamically distill topological states for quantum information applications
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