3,847 research outputs found
Spectral asymptotics for the Schr\"odinger operator on the line with spreading and oscillating potentials
This study is devoted to the asymptotic spectral analysis of multiscale
Schr\"odinger operators with oscillating and decaying electric potentials.
Different regimes, related to scaling considerations, are distinguished. By
means of a normal form filtrating the oscillations, a reduction to a
non-oscillating effective Hamiltonian is performed
A new class of two-layer Green-Naghdi systems with improved frequency dispersion
We introduce a new class of Green-Naghdi type models for the propagation of
internal waves between two (1+1)-dimensional layers of homogeneous, immiscible,
ideal, incompressible, irrotational fluids, vertically delimited by a flat
bottom and a rigid lid. These models are tailored to improve the frequency
dispersion of the original bi-layer Green-Naghdi model, and in particular to
manage high-frequency Kelvin-Helmholtz instabilities, while maintaining its
precision in the sense of consistency. Our models preserve the Hamiltonian
structure, symmetry groups and conserved quantities of the original model. We
provide a rigorous justification of a class of our models thanks to
consistency, well-posedness and stability results. These results apply in
particular to the original Green-Naghdi model as well as to the Saint-Venant
(hydrostatic shallow-water) system with surface tension.Comment: to appear in Stud. Appl. Mat
Mapping the social space of transnational migrants on the basis of their (supra)national belongings: the case of French citizens in Berlin
In traditional migration theory, social self-identification is usually linked with the process and quality of integration and with the nationality of the countries of âoriginâ and of residence. But in the context of a supranational integrated area like the European Union, the self-identification of European people living (also) abroad in another European country can be more complicated. What sorts of identity combinations do they produce in this situation? Could we interpret their choice in the light of their social, economic, cultural capitals and (multi)local integration? Based on an empirical analysis of French citizens in Berlin this article confirms that identity self-combining â not just the identity elements â and the position of the ego in the social space are related. The meaning of the same identity category depends on the respondentâs profiles
Knowledge revision in systems based on an informed tree search strategy : application to cartographic generalisation
Many real world problems can be expressed as optimisation problems. Solving
this kind of problems means to find, among all possible solutions, the one that
maximises an evaluation function. One approach to solve this kind of problem is
to use an informed search strategy. The principle of this kind of strategy is
to use problem-specific knowledge beyond the definition of the problem itself
to find solutions more efficiently than with an uninformed strategy. This kind
of strategy demands to define problem-specific knowledge (heuristics). The
efficiency and the effectiveness of systems based on it directly depend on the
used knowledge quality. Unfortunately, acquiring and maintaining such knowledge
can be fastidious. The objective of the work presented in this paper is to
propose an automatic knowledge revision approach for systems based on an
informed tree search strategy. Our approach consists in analysing the system
execution logs and revising knowledge based on these logs by modelling the
revision problem as a knowledge space exploration problem. We present an
experiment we carried out in an application domain where informed search
strategies are often used: cartographic generalisation.Comment: Knowledge Revision; Problem Solving; Informed Tree Search Strategy;
Cartographic Generalisation., Paris : France (2008
Impartial coloring games
Coloring games are combinatorial games where the players alternate painting
uncolored vertices of a graph one of colors. Each different ruleset
specifies that game's coloring constraints. This paper investigates six
impartial rulesets (five new), derived from previously-studied graph coloring
schemes, including proper map coloring, oriented coloring, 2-distance coloring,
weak coloring, and sequential coloring. For each, we study the outcome classes
for special cases and general computational complexity. In some cases we pay
special attention to the Grundy function
Quantum-like models cannot account for the conjunction fallacy
Human agents happen to judge that a conjunction of two terms is more probable than one of the terms, in contradiction with the rules of classical probabilitiesâthis is the conjunction fallacy. One of the most discussed accounts of this fallacy is currently the quantum-like explanation, which relies on models exploiting the mathematics of quantum mechanics. The aim of this paper is to investigate the empirical adequacy of major quantum-like models which represent beliefs with quantum states. We first argue that they can be tested in three different ways, in a question order effect configuration which is different from the traditional conjunction fallacy experiment. We then carry out our proposed experiment, with varied methodologies from experimental economics. The experimental results we get are at odds with the predictions of the quantum-like models. This strongly suggests that this quantum-like account of the conjunction fallacy fails. Future possible research paths are discussed
Linguistic commodification in tourism
Drawing on fieldwork conducted between 2002 and 2012 in Switzerland, Catalunya and different zones of francophone Canada in sites related to heritage and cultural tourism, we argue that tourism, especially i n multilingual peripheries, is a key site for a sociolinguistic exploration of the political economy of globalization. We link shifts in the role of language in tourism to shifts in phases of capitalism, focusing on the shift from industrial to late capitalism, and in particular on the effects of the commodification of authenticity. We examine the tensions this shift generates in ideologies and practices of language, concerned especially with defining the nature of the tourism product, the public and the management of the tourism process. This results in an as yet unresolved destabilization of hitherto hegemonic discourses linking languages to cultures, identities, nations and States
Oscillatory and localized perturbations of periodic structures and the bifurcation of defect modes
Let denote a periodic function on the real line. The Schr\"odinger
operator, , has spectrum equal to
the union of closed real intervals separated by open spectral gaps. In this
article we study the bifurcation of discrete eigenvalues (point spectrum) into
the spectral gaps for the operator , where is
spatially localized and highly oscillatory in the sense that its Fourier
transform, is concentrated at high frequencies. Our
assumptions imply that may be pointwise large but is
small in an average sense. For the special case where
with smooth, real-valued, localized in
, and periodic or almost periodic in , the bifurcating eigenvalues are at
a distance of order from the lower edge of the spectral gap. We
obtain the leading order asymptotics of the bifurcating eigenvalues and
eigenfunctions. Underlying this bifurcation is an effective Hamiltonian
associated with the lower edge of the spectral band:
where is the Dirac distribution,
and effective-medium parameters are
explicit and independent of . The potentials we consider are a
natural model for wave propagation in a medium with localized, high-contrast
and rapid fluctuations in material parameters about a background periodic
medium.Comment: To appear in SIAM Journal on Mathematical Analysi
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