Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen
OPUS4-4030 misc Henkel, Carsten; Steane, Andrew M.; Kaiser, Robin; Dalibard, Jean A modulated mirror for atomic interferometry A novel atomic beam splitter, using reflection of atoms off an evanescent light wave, is investigated theoretically. The intensity or frequency of the light is modulated in order to create sidebands on the reflected de Broglie wave. The weights and phases of the various sidevands are calculated using three different approaches: the Born approximation, a semiclassical path integral approach, and a numerical solution of the time-dependent Schrdinger equation. We show how this modulated mirror could be used to build practical atomic interferometers. 1994 urn:nbn:de:kobv:517-opus-42279 Institut für Physik und Astronomie
OPUS4-1831 misc Allefeld, Carsten About the derivation of the SCA algorithm In Allefeld & Kurths [2004], we introduced an approach to multivariate phase synchronization analysis in the form of a Synchronization Cluster Analysis (SCA). A statistical model of a synchronization cluster was described, and an abbreviated instruction on how to apply this model to empirical data was given, while an implementation of the corresponding algorithm was (and is) available from the authors. In this letter, the complete details on how the data analysis algorithm is to be derived from the model are filled in. 2006 urn:nbn:de:kobv:517-opus-20137 Institut für Physik und Astronomie
OPUS4-1828 misc Allefeld, Carsten; Kurths, Jürgen An approach to multivariate phase synchronization analysis and its application to event-related potentials A method for the multivariate analysis of statistical phase synchronization phenomena in empirical data is presented. A first statistical approach is complemented by a stochastic dynamic model, to result in a data analysis algorithm which can in a specific sense be shown to be a generic multivariate statistical phase synchronization analysis. The method is applied to EEG data from a psychological experiment, obtaining results which indicate the relevance of this method in the context of cognitive science as well as in other fields. 2004 urn:nbn:de:kobv:517-opus-20106 Institut für Physik und Astronomie
OPUS4-4029 misc Henkel, Carsten; Courtois, Jean-Yves; Aspect, Alain Atomic diffraction by a thin phase grating We present a semiclassical perturbation method for the description of atomic diffraction by a weakly modulated potential. It proceeds in a way similar to the treatment of light diffraction by a thin phase grating, and consists in calculating the atomic wavefunction by means of action integrals along the classical trajectories of the atoms in the absence of the modulated part of the potential. The capabilities and the validity condition of the method are illustrated on the well-known case of atomic diffraction by a Gaussian standing wave. We prove that in this situation the perturbation method is equivalent to the Raman-Nath approximation, and we point out that the usually-considered Raman-Nath validity condition can lead to inaccuracies in the evaluation of the phases of the diffraction amplitudes. The method is also applied to the case of an evanescent wave reflection grating, and an analytical expression for the diffraction pattern at any incidence angle is obtained for the first time. Finally, the application of the method to other situations is briefly discussed. 1994 urn:nbn:de:kobv:517-opus-42269 Institut für Physik und Astronomie
OPUS4-1830 misc Allefeld, Carsten; Frisch, Stefan; Schlesewsky, Matthias Detection of early cognitive processing by event-related phase synchronization analysis In order to investigate the temporal characteristics of cognitive processing, we apply multivariate phase synchronization analysis to event-related potentials. The experimental design combines a semantic incongruity in a sentence context with a physical mismatch (color change). In the ERP average, these result in an N400 component and a P300-like positivity, respectively. The synchronization analysis shows an effect of global desynchronization in the theta band around 288ms after stimulus presentation for the semantic incongruity, while the physical mismatch elicits an increase of global synchronization in the alpha band around 204ms. Both of these effects clearly precede those in the ERP average. Moreover, the delay between synchronization effect and ERP component correlates with the complexity of the cognitive processes. 2005 urn:nbn:de:kobv:517-opus-20126 Institut für Physik und Astronomie
OPUS4-5489 misc Thiel, Marco; Romano, Maria Carmen; Kurths, Jürgen; Rolfs, Martin; Kliegl, Reinhold Generating Surrogates from Recurrences In this paper we present an approach to recover the dynamics from recurrences of a system and then generate (multivariate) twin surrogate (TS) trajectories. In contrast to other approaches, such as the linear-like surrogates, this technique produces surrogates which correspond to an independent copy of the underlying system, i. e. they induce a trajectory of the underlying system visiting the attractor in a different way. We show that these surrogates are well suited to test for complex synchronization, which makes it possible to systematically assess the reliability of synchronization analyses. We then apply the TS to study binocular fixational movements and find strong indications that the fixational movements of the left and right eye are phase synchronized. This result indicates that there might be one centre only in the brain that produces the fixational movements in both eyes or a close link between two centres. 2006 urn:nbn:de:kobv:517-opus-56906 Institut für Psychologie
OPUS4-4031 misc Henkel, Carsten; Courtois, Jean-Yves; Kaiser, Robin; Westbrook, C.; Aspect, Alain Phase shifts of atomic de Broglie waves at an evanescent wave mirror A detailed theoretical investigation of the reflection of an atomic de Broglie wave at an evanescent wave mirror is presented. The classical and the semiclassical descriptions of the reflection process are reviewed, and a full wave-mechanical approach based on the analytical soution of the corresponding Schrödinger equation is presented. The phase shift at reflection is calculated exactly and interpreted in terms of instantaneous reflection of the atom at an effective mirror. Besides the semiclassical regime of reflection describable by the WKB method, a pure quantum regime of reflection is identified in the limit where the incident de Broglie wavelength is large compared to the evanescent wave decay length. 1994 urn:nbn:de:kobv:517-opus-42289 Institut für Physik und Astronomie
OPUS4-1829 misc Allefeld, Carsten; Frisch, Stefan Phase synchronization analysis of event-related potentials in language processing Phase synchronization analysis, including our recently introduced multivariate approach, is applied to event-related EEG data from an experiment on language processing, following a classic psycholinguistic paradigm. For the two types of experimental manipulation distinct effects in overall synchronization are found; for one of them they can also be localized. The synchronization effects occur earlier than those found by the conventional analysis method, indicating that the new approach provides additional information on the underlying neuronal process. 2004 urn:nbn:de:kobv:517-opus-20113 Institut für Linguistik / Allgemeine Sprachwissenschaft
OPUS4-1827 misc Allefeld, Carsten; Kurths, Jürgen Testing for phase synchronization We present different tests for phase synchronization which improve the procedures currently used in the literature. This is accomplished by using a two-samples test setup and by utilizing insights and methods from directional statistics and bootstrap theory. The tests differ in the generality of the situation in which they can be applied as well as in their complexity, including computational cost. A modification of the resampling technique of the bootstrap is introduced, making it possible to fully utilize data from time series. 2004 urn:nbn:de:kobv:517-opus-20091 Institut für Physik und Astronomie
OPUS4-5522 misc Thiel, Marco; Romano, Maria Carmen; Kurths, Jürgen; Rolfs, Martin Twin Surrogates to Test for Complex Synchronisation We present an approach to generate (multivariate) twin surrogates (TS) based on recurrence properties. This technique generates surrogates which correspond to an independent copy of the underlying system, i. e. they induce a trajectory of the underlying system starting at different initial conditions. We show that these surrogates are well suited to test for complex synchronisation and exemplify this for the paradigmatic system of R¨ossler oscillators. The proposed test enables to assess the statistical relevance of a synchronisation analysis from passive experiments which are typical in natural systems. 2006 urn:nbn:de:kobv:517-opus-57231 Institut für Psychologie