Fleischmann, Ragnar

[["dc.bibliographiccitation.artnumber","203903"],["dc.bibliographiccitation.issue","20"],["dc.bibliographiccitation.journal","Physical Review Letters"],["dc.bibliographiccitation.volume","112"],["dc.contributor.author","Metzger, J. J."],["dc.contributor.author","Fleischmann, Ragnar"],["dc.contributor.author","Geisel, Theo"],["dc.date.accessioned","2018-11-07T09:40:01Z"],["dc.date.available","2018-11-07T09:40:01Z"],["dc.date.issued","2014"],["dc.description.abstract","Waves traveling through random media exhibit random focusing that leads to extremely high wave intensities even in the absence of nonlinearities. Although such extreme events are present in a wide variety of physical systems and the statistics of the highest waves is important for their analysis and forecast, it remains poorly understood, in particular, in the regime where the waves are highest. We suggest a new approach that greatly simplifies the mathematical analysis and calculate the scaling and the distribution of the highest waves valid for a wide range of parameters."],["dc.description.sponsorship","DFG research group 760"],["dc.identifier.doi","10.1103/PhysRevLett.112.203903"],["dc.identifier.isi","000336914800005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/33416"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Physical Soc"],["dc.relation.issn","1079-7114"],["dc.relation.issn","0031-9007"],["dc.title","Statistics of Extreme Waves in Random Media"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","013901"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Physical Review Letters"],["dc.bibliographiccitation.volume","111"],["dc.contributor.author","Metzger, J. J."],["dc.contributor.author","Fleischmann, Ragnar"],["dc.contributor.author","Geisel, Theo"],["dc.date.accessioned","2018-11-07T09:22:31Z"],["dc.date.available","2018-11-07T09:22:31Z"],["dc.date.issued","2013"],["dc.description.abstract","Waves traveling through weakly random media are known to be strongly affected by their corresponding ray dynamics, in particular in forming linear freak waves. The ray intensity distribution, which, e. g., quantifies the probability of freak waves is unknown, however, and a theory of how it is approached in an appropriate semiclassical limit of wave mechanics is lacking. We show that this limit is not the usual limit of small wavelengths, but that of decoherence. Our theory, which can describe the intensity distribution for an arbitrary degree of coherence is relevant to a wide range of physical systems, as decoherence is omnipresent in real systems."],["dc.description.sponsorship","DFG Forschergruppe [760]"],["dc.identifier.doi","10.1103/PhysRevLett.111.013901"],["dc.identifier.isi","000321209200006"],["dc.identifier.pmid","23863000"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/29355"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Physical Soc"],["dc.relation.issn","1079-7114"],["dc.relation.issn","0031-9007"],["dc.title","Intensity Fluctuations of Waves in Random Media: What Is the Semiclassical Limit?"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","183902"],["dc.bibliographiccitation.issue","18"],["dc.bibliographiccitation.journal","Physical Review Letters"],["dc.bibliographiccitation.volume","111"],["dc.contributor.author","Barkhofen, S."],["dc.contributor.author","Metzger, J. J."],["dc.contributor.author","Fleischmann, Ragnar"],["dc.contributor.author","Kuhl, U."],["dc.contributor.author","Stoeckmann, H-J."],["dc.date.accessioned","2018-11-07T09:18:11Z"],["dc.date.available","2018-11-07T09:18:11Z"],["dc.date.issued","2013"],["dc.description.abstract","Waves propagating through a weakly scattering random medium show a pronounced branching of the flow accompanied by the formation of freak waves, i.e., extremely intense waves. Theory predicts that this strong fluctuation regime is accompanied by its own fundamental length scale of transport in random media, parametrically different from the mean free path or the localization length. We show numerically how the scintillation index can be used to assess the scaling behavior of the branching length. We report the experimental observation of this scaling using microwave transport experiments in quasi-two-dimensional resonators with randomly distributed weak scatterers. Remarkably, the scaling range extends much further than expected from random caustics statistics."],["dc.description.sponsorship","[Forschergruppe 760]"],["dc.identifier.doi","10.1103/PhysRevLett.111.183902"],["dc.identifier.isi","000326529600004"],["dc.identifier.pmid","24237521"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/28347"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Physical Soc"],["dc.relation.issn","1079-7114"],["dc.relation.issn","0031-9007"],["dc.title","Experimental Observation of a Fundamental Length Scale of Waves in Random Media"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","020601"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Physical Review Letters"],["dc.bibliographiccitation.volume","105"],["dc.contributor.author","Metzger, J. J."],["dc.contributor.author","Fleischmann, Ragnar"],["dc.contributor.author","Geisel, Theo"],["dc.date.accessioned","2018-11-07T08:41:25Z"],["dc.date.available","2018-11-07T08:41:25Z"],["dc.date.issued","2010"],["dc.description.abstract","Even very weak correlated disorder potentials can cause extreme fluctuations in Hamiltonian flows. In two dimensions this leads to a pronounced branching of the flow. Although present in a great variety of physical systems, a quantitative theory of the branching statistics is lacking. Here, we derive an analytical expression for the number of branches valid for all distances from a source. We also derive the scaling relations that make this expression universal for a wide range of random potentials. Our theory has possible applications in many fields ranging from semiconductor to geophysics."],["dc.description.sponsorship","DFG [760]"],["dc.identifier.doi","10.1103/PhysRevLett.105.020601"],["dc.identifier.isi","000279608500001"],["dc.identifier.pmid","20867694"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/19463"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Physical Soc"],["dc.relation.issn","0031-9007"],["dc.title","Universal Statistics of Branched Flows"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","259"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Nature Physics"],["dc.bibliographiccitation.lastpage","+"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Degueldre, Henri"],["dc.contributor.author","Metzger, J. J."],["dc.contributor.author","Geisel, Theo"],["dc.contributor.author","Fleischmann, Ragnar"],["dc.date.accessioned","2018-11-07T10:17:47Z"],["dc.date.available","2018-11-07T10:17:47Z"],["dc.date.issued","2016"],["dc.description.abstract","Tsunamis exhibit surprisingly strong height fluctuations. An in-depth understanding of the mechanisms that lead to these variations in wave height is a prerequisite for reliable tsunami forecasting. It is known, for example, that the presence of large underwater islands(1) or the shape of the tsunami source(2) can affect the wave heights. Here we show that the consecutive effect of even tiny fluctuations in the profile of the ocean floor (the bathymetry) can cause unexpectedly strong fluctuations in the wave height of tsunamis, with maxima several times higher than the average wave height. A novel approach combining stochastic caustic theory and shallow water wave dynamics allows us to determine the typical propagation distance at which the strongly focused waves appear. We demonstrate that owing to this mechanism the small errors present in bathymetry measurements can lead to drastic variations in predicted tsunami heights. Our results show that a precise knowledge of the ocean's bathymetry is absolutely indispensable for reliable tsunami forecasts."],["dc.description.sponsorship","DFG research group 760"],["dc.identifier.doi","10.1038/NPHYS3557"],["dc.identifier.isi","000371505200020"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/41292"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Nature Publishing Group"],["dc.relation.issn","1745-2481"],["dc.relation.issn","1745-2473"],["dc.title","Random focusing of tsunami waves"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]