6,505 research outputs found
Parsimonious Segmentation of Time Series' by Potts Models
Typical problems in the analysis of data sets like time-series or images crucially rely on the extraction of primitive features based on segmentation. Variational approaches are a popular and convenient framework in which such problems can be studied. We focus on Potts models as simple nontrivial instances. The discussion proceeds along two data sets from brain mapping and functional genomics
Quantum black holes from null expansion operators
Using a recently developed quantization of spherically symmetric gravity
coupled to a scalar field, we give a construction of null expansion operators
that allow a definition of general, fully dynamical quantum black holes. These
operators capture the intuitive idea that classical black holes are defined by
the presence of trapped surfaces, that is surfaces from which light cannot
escape outward. They thus provide a mechanism for classifying quantum states of
the system into those that describe quantum black holes and those that do not.
We find that quantum horizons fluctuate, confirming long-held heuristic
expectations. We also give explicit examples of quantum black hole states. The
work sets a framework for addressing the puzzles of black hole physics in a
fully quantized dynamical setting.Comment: 5 pages, version to appear in CQ
Giant anisotropy of Zeeman splitting of quantum confined acceptors in Si/Ge
Shallow acceptor levels in Si/Ge/Si quantum well heterostructures are
characterized by resonant tunneling spectroscopy in the presence of high
magnetic fields. In a perpendicular magnetic field we observe a linear Zeeman
splitting of the acceptor levels. In an in-plane field, on the other hand, the
Zeeman splitting is strongly suppressed. This anisotropic Zeeman splitting is
shown to be a consequence of the huge light hole-heavy hole splitting caused by
a large biaxial strain and a strong quantum confinement in the Ge quantum well.Comment: 5 figures, 4 page
A Class Exercise In Futures Market Trading
The- futures market as we know it today originated around 1850 when a canal linking the Illinois River with Chicago was constructed. This canal enabled country merchants to purchase grain from farmers and ship the grain to Chicago via barges. However, corn could only improve from farms to country merchants during the winter, when country roads were passable. These country merchants were then forced to hold the corn until spring when the canal opened. From the time the country merchants received and paid for the corn from the farmers and the canal opened in the spring, considerable price changes could occur
Tunable quantum spin Hall effect in double quantum wells
The field of topological insulators (TIs) is rapidly growing. Concerning
possible applications, the search for materials with an easily controllable TI
phase is a key issue. The quantum spin Hall effect, characterized by a single
pair of helical edge modes protected by time-reversal symmetry, has been
demonstrated in HgTe-based quantum wells (QWs) with an inverted bandgap. We
analyze the topological properties of a generically coupled HgTe-based double
QW (DQW) and show how in such a system a TI phase can be driven by an
inter-layer bias voltage, even when the individual layers are non-inverted. We
argue, that this system allows for similar (layer-)pseudospin based physics as
in bilayer graphene but with the crucial absence of a valley degeneracy.Comment: 9 pages, 8 figures, extended version (accepted Phys. Rev. B
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