921 research outputs found
Stationary waves on nonlinear quantum graphs: General framework and canonical perturbation theory
In this paper we present a general framework for solving the stationary
nonlinear Schr\"odinger equation (NLSE) on a network of one-dimensional wires
modelled by a metric graph with suitable matching conditions at the vertices. A
formal solution is given that expresses the wave function and its derivative at
one end of an edge (wire) nonlinearly in terms of the values at the other end.
For the cubic NLSE this nonlinear transfer operation can be expressed
explicitly in terms of Jacobi elliptic functions. Its application reduces the
problem of solving the corresponding set of coupled ordinary nonlinear
differential equations to a finite set of nonlinear algebraic equations. For
sufficiently small amplitudes we use canonical perturbation theory which makes
it possible to extract the leading nonlinear corrections over large distances.Comment: 26 page
Indoor Activity Detection and Recognition for Sport Games Analysis
Activity recognition in sport is an attractive field for computer vision
research. Game, player and team analysis are of great interest and research
topics within this field emerge with the goal of automated analysis. The very
specific underlying rules of sports can be used as prior knowledge for the
recognition task and present a constrained environment for evaluation. This
paper describes recognition of single player activities in sport with special
emphasis on volleyball. Starting from a per-frame player-centered activity
recognition, we incorporate geometry and contextual information via an activity
context descriptor that collects information about all player's activities over
a certain timespan relative to the investigated player. The benefit of this
context information on single player activity recognition is evaluated on our
new real-life dataset presenting a total amount of almost 36k annotated frames
containing 7 activity classes within 6 videos of professional volleyball games.
Our incorporation of the contextual information improves the average
player-centered classification performance of 77.56% by up to 18.35% on
specific classes, proving that spatio-temporal context is an important clue for
activity recognition.Comment: Part of the OAGM 2014 proceedings (arXiv:1404.3538
Quantum Corrections to Fidelity Decay in Chaotic Systems
By considering correlations between classical orbits we derive semiclassical
expressions for the decay of the quantum fidelity amplitude for classically
chaotic quantum systems, as well as for its squared modulus, the fidelity or
Loschmidt echo. Our semiclassical results for the fidelity amplitude agree with
random matrix theory (RMT) and supersymmetry predictions in the universal Fermi
golden rule regime. The calculated quantum corrections can be viewed as arising
from a static random perturbation acting on nearly self-retracing interfering
paths, and hence will be suppressed for time-varying perturbations. Moreover,
using trajectory-based methods we show a relation, recently obtained in RMT,
between the fidelity amplitude and the cross-form factor for parametric level
correlations. Beyond RMT, we compute Ehrenfest-time effects on the fidelity
amplitude. Furthermore our semiclassical approach allows for a unified
treatment of the fidelity, both in the Fermi golden rule and Lyapunov regimes,
demonstrating that quantum corrections are suppressed in the latter.Comment: 14 pages, 4 figure
A sub-determinant approach for pseudo-orbit expansions of spectral determinants in quantum maps and quantum graphs
We study implications of unitarity for pseudo-orbit expansions of the
spectral determinants of quantum maps and quantum graphs. In particular, we
advocate to group pseudo-orbits into sub-determinants. We show explicitly that
the cancellation of long orbits is elegantly described on this level and that
unitarity can be built in using a simple sub-determinant identity which has a
non-trivial interpretation in terms of pseudo-orbits. This identity yields much
more detailed relations between pseudo orbits of different length than known
previously. We reformulate Newton identities and the spectral density in terms
of sub-determinant expansions and point out the implications of the
sub-determinant identity for these expressions. We analyse furthermore the
effect of the identity on spectral correlation functions such as the
auto-correlation and parametric cross correlation functions of the spectral
determinant and the spectral form factor.Comment: 25 pages, one figur
Getting an Heir: Adoption and the Construction of Kinship in Late Imperial China
Humanities Open Book Program, a joint initiative of the National Endowment for the Humanities and the Andrew W. Mellon FoundationThe need for heirs in any traditional society is a compelling one. In traditional China, where inheritance and notions of filiality depended on the production of progeny, the need was nearly absolute. As Ann Waltner makes clear in this broadly researched study of adoption in the late Ming and early Ch'ing periods, the getting of an heir was a complex, even paradoxical undertaking. Although adoption involving persons of the same surname was the only arrangement ritually and legally sanctioned in Chinese society, adoption of persons of a different surname was a relatively common practice. Using medical and ritual texts, legal codes, local gazetteers, biography, and fiction, Waltner examines the multiple dimensions of the practice of adoption and identifies not only the dominant ideology prohibiting adoption across surname lines, but also a parallel discourse justifying the practice
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