161,580 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
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
Impact of two mass-scale oscillations on the analysis of atmospheric and reactor neutrino data
We study the stability of the results of 3-nu oscillation analysis of
atmospheric and reactor neutrino data under departures of the one--dominant
mass scale approximation. In order to do so we perform the analysis of
atmospheric and reactor neutrino data in terms of three--neutrino oscillations
where the effect of both mass differences is explicitly considered. We study
the allowed parameter space resulting from this analysis as a function of the
mass splitting hierarchy parameter alpha = Delta m^2/Delta M^2 which
parametrizes the departure from the one--dominant mass scale approximation. We
consider schemes with both direct and inverted mass ordering. Our results show
that in the analysis of atmospheric data the derived range of the largest mass
splitting, Delta M^2$, is stable while the allowed ranges of mixing angles
sin^2 theta_{23} and sin^2 theta_{13} are wider than those obtained in the
one--dominant mass scale approximation. Inclusion of the CHOOZ reactor data in
the analysis results into the reduction of the parameter space in particular
for the mixing angles. As a consequence the final allowed ranges of parameters
from the combined analysis are only slightly broader than when obtained in the
one--dominant mass scale approximation.Comment: Updated data, references added and typos corrected. Version to appear
in Eur.Phys.J.
Honoring, Training, and Building a Statewide Network of Elder Activists: The California Senior Leaders Program (2002-2012)
This case study explores the first decade (2002-2012) of the California Senior Leaders Program (CSLP), including participants' creation of a formal advocacy group, the California Senior Leaders Alliance. Grounded in concerns with ageism and invisibility, the CSLP provides recognition and support for diverse California elders engaged in community building and social justice work. This study employs qualitative analysis of data from participant interviews, event evaluations, program documents, video footage, and participant observation. Findings show emotional, learning, and networking benefits for participants, intergenerational influences, collective capacity and coalition building, and contributions to policy. Program challenges are described, and future directions discussed. © 2013 Copyright Taylor and Francis Group, LLC
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
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