Discrimination of low-frequency tones employs temporal fine structure

An auditory neuron can preserve the temporal fine structure of a low-frequency tone by phase-locking its response to the stimulus. Apart from sound localization, however, little is known about the role of this temporal information for signal processing in the brain. Through psychoacoustic studies we provide direct evidence that humans employ temporal fine structure to discriminate between frequencies. To this end we construct tones that are based on a single frequency but in which, through the concatenation of wavelets, the phase changes randomly every few cycles. We then test the frequency discrimination of these phase-changing tones, of control tones without phase changes, and of short tones that consist of a single wavelets. For carrier frequencies below a few kilohertz we find that phase changes systematically worsen frequency discrimination. No such effect appears for higher carrier frequencies at which temporal information is not available in the central auditory system.Comment: 12 pages, 3 figure

Note on clock synchronization and Edwards transformations

Edwards transformations relating inertial frames with arbitrary clock synchronization are reminded and put in more general setting. Their group theoretical context is described.Comment: 11 pages, no figures; final version, to appear in Foundations of Physics Letter

Uncertainties inherent in the decomposition of a Transformation

This contribution adds to the points on the <indeterminacy of special relativity> made by De Abreu and Guerra. We show that the Lorentz Transformation can be composed by the physical observations made in a frame K of events in a frame K-prime viz i) objects in K-prime are moving at a speed v relative to K, ii) distances and time intervals measured by K-prime are at variance with those measured by K and iii) the concept of simultaneity is different in K-prime compared to K. The order in which the composition is executed determines the nature of the middle aspect (ii). This essential uncertainty of the theory can be resolved only by a universal synchronicity as discussed in [1] based on the unique frame in which the one way speed of light is constant in all directions.Comment: 10 pages including an appendix. Published in the European Journal of Physics as a Comment. Eur. J. Phys. 29 (2008) L13-L1

Dual contribution to amplification in the mammalian inner ear

The inner ear achieves a wide dynamic range of responsiveness by mechanically amplifying weak sounds. The enormous mechanical gain reported for the mammalian cochlea, which exceeds a factor of 4,000, poses a challenge for theory. Here we show how such a large gain can result from an interaction between amplification by low-gain hair bundles and a pressure wave: hair bundles can amplify both their displacement per locally applied pressure and the pressure wave itself. A recently proposed ratchet mechanism, in which hair-bundle forces do not feed back on the pressure wave, delineates the two effects. Our analytical calculations with a WKB approximation agree with numerical solutions.Comment: 4 pages, 4 figure

Simultaneity as an Invariant Equivalence Relation

This paper deals with the concept of simultaneity in classical and relativistic physics as construed in terms of group-invariant equivalence relations. A full examination of Newton, Galilei and Poincar\'e invariant equivalence relations in $\R^4$ is presented, which provides alternative proofs, additions and occasionally corrections of results in the literature, including Malament's theorem and some of its variants. It is argued that the interpretation of simultaneity as an invariant equivalence relation, although interesting for its own sake, does not cut in the debate concerning the conventionality of simultaneity in special relativity.Comment: Some corrections, mostly of misprints. Keywords: special relativity, simultaneity, invariant equivalence relations, Malament's theore

Preface "Methods and strategies to evaluate landslide hazard and risk"

Federal Institute for Geosciences and Natural Resources, Hannover, GermanyThe special issue of Natural Hazards and Earth SystemSciences entitled "Methods and strategies to evaluatelandslide hazard and risk", which we had the fortune to edit,contains a selected set of contributions originally presentedat the General Assembly of the European GeosciencesUnion, in Vienna, Austria, on 13–18 April 2008. Themeeting proved to be a valuable opportunity to discussand compare methods, techniques and tools for discovering,evaluating, avoiding and mitigating landslide hazards andthe related risk. Novel approaches and case studies ofheuristic, statistical, and physically based models to evaluatelandslide hazards and risk at different geographical scalesand in different physiographic environments were presented.During the meeting, Theo van Asch, 2008 Sergey Solovievmedallist, gave an inspiring presentation on "Some issues andchallenges in landslide hazard modelling". This presentationsummarized the state-of-the-art, physically based landslidemodelling, and set the path for future research on thischallenging topic.The special issue contains six of the 29 oral and postercontributions originally presented and discussed by morethan 50authors at the meeting. The six papers cover alarge spectrum of topics, from site-specific investigationsto global-scale landslide hazard assessments. van Aschand Malet (2009) focused on the potential transition ofsliding blocks (slumps) into flow-like processes due tothe generation of excess pore water pressure in undrainedconditions. The generation of excess pore water pressuremay be the consequence of the deformation of the landslidebody during motion. The authors propose and discuss twomodel concepts that are tested on two slumps that havedeveloped in secondary scarps of the Super-Sauze mudslidein the Barcelonnette area, Southern Alps, France.Correspondence to: P. Reichenbach([email protected])Gunther and Thiel (2009) evaluated structurally-controlled¨failure susceptibility of fractured Cretaceous chalk rocks andtopographically-controlled shallow landslide susceptibilityof overlying glacial sediments in the Jasmund cliff area,Rugen Island, Germany. These authors adopted a combined¨methodology that involved spatially distributed kinematicalrock slope failure testing with tectonic fabric data, andphysically-based and inventory-based shallow landslidesusceptibility analyses. Romstad et al. (2009) presentedan innovative approach for regional hazard assessment ofNorwegian lakes exposed to tsunamis that can generatecatastrophic rockslides. The method successfully distin-guished between lakes with high and low rockslide potential.For each lake, the rockfall potential was determined basedon the topographical setting. For this reason, the rockfallpotential does not measure the probability of rockslides in thelakes. Van Den Eeckhaut et al. (2009) discussed a combinedlandslide inventory and susceptibility assessment based ondifferent mapping units carried out in the Flemish Ardennes,Belgium. The landslide susceptibility zonation was preparedthrough heuristic combination of, (i) a regional landslideinventory, (ii) a grid-cell-based map showing susceptibilityto landslide initiation, and (iii) a topographic-unit-based mapshowing the susceptibility to landslide spatial occurrence.Garc´ia-Rodr ´iguez and Malpica (2010) presented an approachfor assessing earthquake-triggered landslide susceptibilityusing artificial neural networks (ANN) in El Salvador.Modelling results were checked using independent landslideinformation, and revealed a good agreement between thelandslide inventory and the high susceptibility zoning. Thenew susceptibility zonation was compared critically to anexisting susceptibility zonation obtained through logisticregression analysis. Kirschbaum et al. (2009) presented apreliminary global landslide hazard algorithm developed toestimate areas of potential landslide occurrence in near real-time by combining a calculation of landslide susceptibilitywith satellite-derived rainfall estimates to forecast areas withPublished by Copernicus Publications on behalf of the European Geosciences Union

Coexistence in a One-Dimensional Cyclic Dominance Process

Cyclic (rock-paper-scissors-type) population models serve to mimic complex species interactions. Focusing on a paradigmatic three-species model with mutations in one dimension, we observe an interplay between equilibrium and non-equilibrium processes in the stationary state. We exploit these insights to obtain asymptotically exact descriptions of the emerging reactive steady state in the regimes of high and low mutation rates. The results are compared to stochastic lattice simulations. Our methods and findings are potentially relevant for the spatio-temporal evolution of other non-equilibrium stochastic processes.Comment: 4 pages, 4 figures and 2 pages of Supplementary Material. To appear in Physical Review