18,976 research outputs found
Classical intermittency and quantum Anderson transition
We investigate the quantum properties of 1D quantum systems whose classical
counterpart presents intermittency.
The spectral correlations are expressed in terms of the eigenvalues of an
anomalous diffusion operator by using recent semiclassical techniques. For
certain values of the parameters the spectral properties of our model show
similarities with those of a disordered system at the Anderson transition. In
Hamiltonian systems, intermittency is closely related to the presence of
cantori in the classical phase space. We suggest, based on this relation, that
our findings may be relevant for the description of the spectral correlations
of (non-KAM) Hamiltonians with a classical phase space filled by cantori.
Finally we discuss the extension of our results to higher dimensions and
their relation to Anderson models with long range hopping.Comment: 4 pages, typos corrected, references adde
Introduction to Constellar Theory in Multicultural Education Pedagogy
The majority of education and social science ideas subscribe to a hierarchical ideology that not only necessitates but also obligates an always-already dialectic. Such a dialectical fetish and intellectual relegation is grounded in Marxist ideology, which has influenced a vast majority of cultural studies and social science theories. Constellar Theory challenges the hierarchical model ideology in concept and pedagogy to complicate and exhibit a more intricate matrix of considerations to move the multicultural education discourse in possible new directions
Classical and quantum anomalous diffusion in a system of 2-kicked Quantum Rotors
We study the dynamics of cold atoms subjected to {\em pairs} of closely
time-spaced -kicks from standing waves of light. The classical phase
space of this system is partitioned into momentum cells separated by trapping
regions. In a certain range of parameters it is shown that the classical motion
is well described by a process of anomalous diffusion. We investigate in detail
the impact of the underlying classical anomalous diffusion on the quantum
dynamics with special emphasis on the phenomenon of dynamical localization.
Based on the study of the quantum density of probability, its second moment and
the return probability we identify a region of weak dynamical localization
where the quantum diffusion is still anomalous but the diffusion rate is slower
than in the classical case. Moreover we examine how other relevant time scales
such as the quantum-classical breaking time or the one related to the beginning
of full dynamical localization are modified by the classical anomalous
diffusion. Finally we discuss the relevance of our results for the
understanding of the role of classical cantori in quantum mechanics.Comment: 9 pages, 3 figure
The QCD vacuum as a disordered medium: A simplified model for the QCD Dirac operator
We model the QCD Dirac operator as a power-law random banded matrix (RBM)
with the appropriate chiral symmetry. Our motivation is the form of the Dirac
operator in a basis of instantonic zero modes with a corresponding gauge
background of instantons. We compare the spectral correlations of this model to
those of an instanton liquid model (ILM) and find agreement well beyond the
Thouless energy. In the bulk of the spectrum the (dimensionless) Thouless
energy of the RBM scales with the square root of system size in agreement with
the ILM and chiral perturbation theory. Near the origin the scaling of the
(dimensionless) Thouless energy in the RBM remains the same as in the bulk
which agrees with chiral perturbation theory but not with the ILM. Finally we
discuss how this RBM should be modified in order to describe the spectral
correlations of the QCD Dirac operator at the finite temperature chiral
restoration transition.Comment: 4 pages, 3 figure
The attempted merger between General Electric and Honeywell, a case study of transatlantic conflict
\cf1\f1 This paper analyzes how State aid affects and distorts competition and trade within and across jurisdictions. We identify the circumstances in which state aid is likely to involve the largest distortions. In the context of the paper distortion of competition" is interpreted as the effect on rivals\f2\rquote\f1 profits. We consider three types of state intervention, namely subsidies which affect marginal cost, entry and quality and analyse whether particular market characteristics are robust indicators of the magnitude of the distortions. We obtain the following results: (i) it appears that concentration is a fairly robust indicator; (ii) A high degree of substitution across differentiated products is not a robust indicator of the magnitude of the distortions. Its effect depends on the type of state intervention; (iii) The substitution among domestic products may have opposite effects respectively on domestic and foreign firms. In particular, when the market is not concentrated and state aid takes the form of a production subsidy, a stronger substitution among domestic products will reduce the distortions felt by the foreign firm (but increase that felt by domestic rivals); Finally, (iv) the paper demonstrates that the impact of selective State aid on market prices and competitors can depend on the particular characteristics of the market JEL Classification numbers: K21; L10; L40State aids; EU Antitrust; distortions of competition
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