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Search Results: 1 - 10 of 407322 matches for " H. -J. St?ckmann "
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Parametric correlations versus fidelity decay: the symmetry breaking case
H. Kohler,T. Nagao,H. -J. Stckmann
Physics , 2011, DOI: 10.1103/PhysRevE.84.061133
Abstract: We derive fidelity decay and parametric energy correlations for random matrix ensembles where time--reversal invariance of the original Hamiltonian is broken by the perturbation. Like in the case of a symmetry conserving perturbation a simple relation between both quantities can be established.
Universal transport properties of open microwave cavities with and without time-reversal symmetry
H. Schanze,M. Martinez-Mares,C. H. Lewenkopf,H. -J. Stckmann
Physics , 2004, DOI: 10.1103/PhysRevE.71.016223
Abstract: We measure the transmission through asymmetric and reflection-symmetric chaotic microwave cavities in dependence of the number of attached wave guides. Ferrite cylinders are placed inside the cavities to break time-reversal symmetry. The phase-breaking properties of the ferrite and its range of applicability are discussed in detail. Random matrix theory predictions for the distribution of transmission coefficients T and their energy derivative dT/dE are extended to account for absorption. Using the absorption strength as a fitting parameter, we find good agreement between universal transmission fluctuations predicted by theory and the experimental data.
Density and Correlation functions of vortex and saddle points in open billiard systems
R. H?hmann,U. Kuhl,H. -J. Stckmann,J. D. Urbina,M. Dennis
Physics , 2008, DOI: 10.1103/PhysRevE.79.016203
Abstract: We present microwave measurements for the density and spatial correlation of current critical points in an open billiard system, and compare them with the predictions of the Random Wave Model (RWM). In particular, due to a novel improvement of the experimental set-up, we determine experimentally the spatial correlation of saddle points of the current field. An asymptotic expression for the vortex-saddle and saddle-saddle correlation functions based on the RWM is derived, with experiment and theory agreeing well. We also derive an expression for the density of saddle points in the presence of a straight boundary with general mixed boundary conditions in the RWM, and compare with experimental measurements of the vortex and saddle density in the vicinity of a straight wall satisfying Dirichlet conditions.
Measurement of long-range wavefunction correlations in an open microwave billiard
Y. -H. Kim,U. Kuhl,H. -J. Stckmann,P. W. Brouwer
Physics , 2004, DOI: 10.1103/PhysRevLett.94.036804
Abstract: We investigate the statistical properties of wavefunctions in an open chaotic cavity. When the number of channels in the openings of the billiard is increased by varying the frequency, wavefunctions cross over from real to complex. The distribution of the phase rigidity, which characterizes the degree to which a wavefunction is complex, and long-range correlations of intensity and current density are studied as a function of the number of channels in the openings. All measured quantities are in perfect agreement with theoretical predictions.
Tunable Fano Resonances in Transport through Microwave Billiards
S. Rotter,F. Libisch,J. Burgd?rfer,U. Kuhl,H. -J. Stckmann
Physics , 2003, DOI: 10.1103/PhysRevE.69.046208
Abstract: We present a tunable microwave scattering device that allows the controlled variation of Fano line shape parameters in transmission through quantum billiards. Transport in this device is nearly fully coherent. By comparison with quantum calculations, employing the modular recursive Green's-function method, the scattering wave function and the degree of residual decoherence can be determined. The parametric variation of Fano line shapes in terms of interacting resonances is analyzed.
Correlations of electromagnetic fields in chaotic cavities
B. Eckhardt,U. D?rr,U. Kuhl,H. -J. Stckmann
Physics , 1999, DOI: 10.1209/epl/i1999-00233-9
Abstract: We consider the fluctuations of electromagnetic fields in chaotic microwave cavities. We calculate the transversal and longitudinal correlation function based on a random wave assumption and compare the predictions with measurements on two- and three-dimensional microwave cavities.
Spectral properties of microwave graphs with local absorption
M. Allgaier,S. Gehler,S. Barkhofen,H. -J. Stckmann,U. Kuhl
Physics , 2013, DOI: 10.1103/PhysRevE.89.022925
Abstract: The influence of absorption on the spectra of microwave graphs has been studied experimentally. The microwave networks were made up of coaxial cables and T junctions. First, absorption was introduced by attaching a 50 Ohm load to an additional vertex for graphs with and without time-reversal symmetry. The resulting level-spacing distributions were compared with a generalization of the Wigner surmise in the presence of open channels proposed recently by Poli et al. [Phys. Rev. Lett. 108, 174101 (2012)]. Good agreement was found using an effective coupling parameter. Second, absorption was introduced along one individual bond via a variable microwave attenuator, and the influence of absorption on the length spectrum was studied. The peak heights in the length spectra corresponding to orbits avoiding the absorber were found to be independent of the attenuation, whereas, the heights of the peaks belonging to orbits passing the absorber once or twice showed the expected decrease with increasing attenuation.
Microwave fidelity studies by varying antenna coupling
B. K?ber,U. Kuhl,H. -J. Stckmann,T. Gorin,D. V. Savin,T. H. Seligman
Physics , 2010, DOI: 10.1103/PhysRevE.82.036207
Abstract: The fidelity decay in a microwave billiard is considered, where the coupling to an attached antenna is varied. The resulting quantity, coupling fidelity, is experimentally studied for three different terminators of the varied antenna: a hard wall reflection, an open wall reflection, and a 50 Ohm load, corresponding to a totally open channel. The model description in terms of an effective Hamiltonian with a complex coupling constant is given. Quantitative agreement is found with the theory obtained from a modified VWZ approach [Verbaarschot et al, Phys. Rep. 129, 367 (1985)].
Surface scattering and band gaps in rough waveguides and nanowires
O. Dietz,H. -J. Stckmann,U. Kuhl,F. M. Izrailev,N. M. Makarov,J. Doppler,F. Libisch,S. Rotter
Physics , 2012, DOI: 10.1103/PhysRevB.86.201106
Abstract: The boundaries of waveguides and nanowires have drastic influence on their coherent scattering properties. Designing the boundary profile is thus a promising approach for transmission and band-gap engineering with many applications. By performing an experimental study of microwave transmission through rough waveguides we demonstrate that a recently proposed surface scattering theory can be employed to predict the measured transmission properties from the boundary profiles and vice versa. A new key ingredient of this theory is a scattering mechanism which depends on the squared gradient of the surface profiles. We demonstrate the non-trivial effects of this scattering mechanism by detailed mode-resolved microwave measurements and numerical simulations.
Dynamical tunneling in mushroom billiards
A. B?cker,R. Ketzmerick,S. L?ck,M. Robnik,G. Vidmar,R. H?hmann,U. Kuhl,H. -J. Stckmann
Physics , 2008, DOI: 10.1103/PhysRevLett.100.174103
Abstract: We study the fundamental question of dynamical tunneling in generic two-dimensional Hamiltonian systems by considering regular-to-chaotic tunneling rates. Experimentally, we use microwave spectra to investigate a mushroom billiard with adjustable foot height. Numerically, we obtain tunneling rates from high precision eigenvalues using the improved method of particular solutions. Analytically, a prediction is given by extending an approach using a fictitious integrable system to billiards. In contrast to previous approaches for billiards, we find agreement with experimental and numerical data without any free parameter.
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