354 research outputs found
NLC-2 graph recognition and isomorphism
NLC-width is a variant of clique-width with many application in graph
algorithmic. This paper is devoted to graphs of NLC-width two. After giving new
structural properties of the class, we propose a -time algorithm,
improving Johansson's algorithm \cite{Johansson00}. Moreover, our alogrithm is
simple to understand. The above properties and algorithm allow us to propose a
robust -time isomorphism algorithm for NLC-2 graphs. As far as we
know, it is the first polynomial-time algorithm.Comment: soumis \`{a} WG 2007; 12
Dependence Logic with Generalized Quantifiers: Axiomatizations
We prove two completeness results, one for the extension of dependence logic
by a monotone generalized quantifier Q with weak interpretation, weak in the
meaning that the interpretation of Q varies with the structures. The second
result considers the extension of dependence logic where Q is interpreted as
"there exists uncountable many." Both of the axiomatizations are shown to be
sound and complete for FO(Q) consequences.Comment: 17 page
Seismic monitoring and verification for the Co2CRC Ottway Basin project
The Otway Project conducted under the Australian Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) is the first of its kind, where CO2 is injected into a depleted gas reservoir. The use of depleted fields for CO2 storage is likely to become widely adopted globally and, therefore, the project will provide important experience for monitoring under these conditions. However, such scenario is not favorable for the application of geophysical techniques for the purpose of CO2 monitoring and verification (M&V) because the injection of CO2 into a CH4 depleted reservoir is modeled to produce very subtle changes in elastic properties of the reservoir rock which may be very difficult to measure. Consequently geophysical program for the Otway site was design according to the expected time-lapse effects. It combines both surface and borehole seismic methods. Surface seismic should provide a global vision of the underground and an indirect confirmation of the CO2 containment by recording no differences between the successive time-lapse experiments. Vertical Seismic Profile (VSP) surveys are expected to provide an improved characterization of the reservoir and hopefully a direct indication of the fluid distribution and/or its potential upward migration along the reservoir bounding fault pattern. Indeed the results of the current analysis of both pre-base line (test) and base-line 2D and 3D VSP data are encouraging. The availability of vector wave field (three-component) data recorded in VSP surveys should significantly improve the outcomes of M&V program at Naylor site
Metal--topological-insulator transition in the quantum kicked rotator with Z2 symmetry
The quantum kicked rotator is a periodically driven dynamical system with a
metal-insulator transition. We extend the model so that it includes phase
transitions between a metal and a topological insulator, in the universality
class of the quantum spin Hall effect. We calculate the Z2 topological
invariant using a scattering formulation that remains valid in the presence of
disorder. The scaling laws at the phase transition can be studied efficiently
by replacing one of the two spatial dimensions with a second incommensurate
driving frequency. We find that the critical exponent does not depend on the
topological invariant, in agreement with earlier independent results from the
network model of the quantum spin Hall effect.Comment: 5 figures, 6 page
Zero-voltage conductance peak from weak antilocalization in a Majorana nanowire
We show that weak antilocalization by disorder competes with resonant Andreev
reflection from a Majorana zero-mode to produce a zero-voltage conductance peak
of order e^2/h in a superconducting nanowire. The phase conjugation needed for
quantum interference to survive a disorder average is provided by particle-hole
symmetry - in the absence of time-reversal symmetry and without requiring a
topologically nontrivial phase. We identify methods to distinguish the Majorana
resonance from the weak antilocalization effect.Comment: 13 pages, 8 figures. Addendum, February 2014: Appendix B shows
results for weak antilocalization in the circular ensemble. (This appendix is
not in the published version.
A New Method to Estimate the Noise in Financial Correlation Matrices
Financial correlation matrices measure the unsystematic correlations between
stocks. Such information is important for risk management. The correlation
matrices are known to be ``noise dressed''. We develop a new and alternative
method to estimate this noise. To this end, we simulate certain time series and
random matrices which can model financial correlations. With our approach,
different correlation structures buried under this noise can be detected.
Moreover, we introduce a measure for the relation between noise and
correlations. Our method is based on a power mapping which efficiently
suppresses the noise. Neither further data processing nor additional input is
needed.Comment: 25 pages, 8 figure
On Measuring Non-Recursive Trade-Offs
We investigate the phenomenon of non-recursive trade-offs between
descriptional systems in an abstract fashion. We aim at categorizing
non-recursive trade-offs by bounds on their growth rate, and show how to deduce
such bounds in general. We also identify criteria which, in the spirit of
abstract language theory, allow us to deduce non-recursive tradeoffs from
effective closure properties of language families on the one hand, and
differences in the decidability status of basic decision problems on the other.
We develop a qualitative classification of non-recursive trade-offs in order to
obtain a better understanding of this very fundamental behaviour of
descriptional systems
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Spring School on Language, Music, and Cognition: Organizing Events in Time
The interdisciplinary spring school “Language, music, and cognition: Organizing events in time” was held from February 26 to March 2, 2018 at the Institute of Musicology of the University of Cologne. Language, speech, and music as events in time were explored from different perspectives including evolutionary biology, social cognition, developmental psychology, cognitive neuroscience of speech, language, and communication, as well as computational and biological approaches to language and music. There were 10 lectures, 4 workshops, and 1 student poster session.
Overall, the spring school investigated language and music as neurocognitive systems and focused on a mechanistic approach exploring the neural substrates underlying musical, linguistic, social, and emotional processes and behaviors. In particular, researchers approached questions concerning cognitive processes, computational procedures, and neural mechanisms underlying the temporal organization of language and music, mainly from two perspectives: one was concerned with syntax or structural representations of language and music as neurocognitive systems (i.e., an intrapersonal perspective), while the other emphasized social interaction and emotions in their communicative function (i.e., an interpersonal perspective). The spring school not only acted as a platform for knowledge transfer and exchange but also generated a number of important research questions as challenges for future investigations
A Memetic Analysis of a Phrase by Beethoven: Calvinian Perspectives on Similarity and Lexicon-Abstraction
This article discusses some general issues arising from the study of similarity in music, both human-conducted and computer-aided, and then progresses to a consideration of similarity relationships between patterns in a phrase by Beethoven, from the first movement of the Piano Sonata in A flat major op. 110 (1821), and various potential memetic precursors. This analysis is followed by a consideration of how the kinds of similarity identified in the Beethoven phrase might be understood in psychological/conceptual and then neurobiological terms, the latter by means of William Calvin’s Hexagonal Cloning Theory. This theory offers a mechanism for the operation of David Cope’s concept of the lexicon, conceived here as a museme allele-class. I conclude by attempting to correlate and map the various spaces within which memetic replication occurs
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