TY  - BOOK
A1  - Scheel, S.
A1  - Seehafer, Norbert
T1  - Bifurcation to Oscillations in three-dimensional Rayleigh-Bénard convection
T3  - Preprint NLD
Y1  - 1997
SN  - 1432-2935
VL  - 39
PB  - Univ. Potsdam
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Scheel, S.
A1  - Seehafer, Norbert
T1  - Bifurcation to oscillations in three-dimensional Rayleigh-Bénard convection
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Demircan, Ayhan
A1  - Scheel, S.
A1  - Seehafer, Norbert
T1  - Heteroclinic behavior in rotating Rayleigh-Benard convection
N2  - We investigate numerically the appearance of heteroclinic behavior in a three-dimensional, buoyancy-driven fluid layer with stress-free top and bottom boundaries, a square horizontal periodicity with a small aspect ratio, and rotation at low to moderate rates about a vertical axis. The Prandtl number is 6.8. If the rotation is not too slow, the skewed-varicose instability leads from stationary rolls to a stationary mixed-mode solution, which in turn loses stability to a heteroclinic cycle formed by unstable roll states and connections between them. The unstable eigenvectors of these roll states are also of the skewed-varicose or mixed-mode type and in some parameter regions skewed-varicose like shearing oscillations as well as square patterns are involved in the cycle. Always present weak noise leads to irregular horizontal translations of the convection pattern and makes the dynamics chaotic, which is verified by calculating Lyapunov exponents. In the nonrotating case the primary rolls lose, depending on the aspect ratio, stability to traveling waves or a stationary square pattern. We also study the symmetries of the solutions at the intermittent fixed points in the heteroclinic cycle.
Y1  - 2000
UR  - http://link.springer.de/link/service/journals/10051/bibs/0013004/00130765.htm
ER  - 
TY  - JOUR
A1  - Eisert, Jens
A1  - Browne, Dan E.
A1  - Scheel, S.
A1  - Plenio, M. B.
T1  - Distillation of continuous-variable entanglement with optical means
N2  - We present an event-ready procedure that is capable of distilling Gaussian two-mode entangled states from a supply of weakly entangled states that have become mixed in a decoherence process. This procedure relies on passive optical elements and photon detectors distinguishing the presence and the absence of photons, but does not make use of photon counters. We identify fixed points of the iteration map, and discuss in detail its convergence properties. Necessary and sufficient criteria for the convergence to two-mode Gaussian states are presented. On the basis of various examples we discuss the performance of the procedure as far as the increase of the degree of entanglement and two-mode squeezing is concerned. Finally, we consider imperfect operations and outline the robustness of the scheme under non- unit detection efficiencies of the detectors. This analysis implies that the proposed protocol can be implemented with currently available technology and detector efficiencies. (C) 2004 Elsevier Inc. All rights reserved
Y1  - 2004
SN  - 0003-4916
ER  -