4,753 research outputs found
Chaotic behavior of the Compound Nucleus, open Quantum Dots and other nanostructures
It is well established that physical systems exhibit both ordered and chaotic
behavior. The chaotic behavior of nanostructure such as open quantum dots has
been confirmed experimentally and discussed exhaustively theoretically. This is
manifested through random fluctuations in the electronic conductance. What
useful information can be extracted from this noise in the conductance? In this
contribution we shall address this question. In particular, we will show that
the average maxima density in the conductance is directly related to the
correlation function whose characteristic width is a measure of energy- or
applied magnetic field- correlation length. The idea behind the above has been
originally discovered in the context of the atomic nucleus, a mesoscopic
system. Our findings are directly applicable to graphene.Comment: 10 pages, 5 figures. Contribution to: "4th International Workshop on
Compound-Nuclear Reactions and Related Topics (CNR*13)", October 7-11, 2013,
Maresias, Brazil. To appear in the proceeding
A study of local approximation for polarization potentials
We discuss the derivation of an equivalent \textit{l}-independent
polarization potential for use in the optical Schr\"{o}dinger equation that
describes the elastic scattering of heavy ions. Three diffferent methods are
used for this purpose. Application of our theory to the low energy scattering
of the halo nucleus Li from a C target is made. It is found that
the notion of \textit{l}-independent polarization potential has some validity
but can not be a good substitute for the \textit{l}-dependent local equivalent
Feshbach polarization potential.Comment: 8 pages, 4 figure
Matrix Elements of Random Operators and Discrete Symmetry Breaking in Nuclei
It is shown that several effects are responsible for deviations of the
intensity distributions from the Porter-Thomas law. Among these are genuine
symmetry breaking, such as isospin; the nature of the transition operator;
truncation of the Hilbert space in shell model calculations and missing
transitionsComment: 8 pages, 3 figure
Deformed Gaussian Orthogonal Ensemble Analysis of the Interacting Boson Model
A Deformed Gaussian Orthogonal Ensemble (DGOE) which interpolates between the
Gaussian Orthogonal Ensemble and a Poissonian Ensemble is constructed. This new
ensemble is then applied to the analysis of the chaotic properties of the low
lying collective states of nuclei described by the Interacting Boson Model
(IBM). This model undergoes a transition order-chaos-order from the
limit to the limit. Our analysis shows that the quantum fluctuations of
the IBM Hamiltonian, both of the spectrum and the eigenvectors, follow the
expected behaviour predicted by the DGOE when one goes from one limit to the
other.Comment: 10 pages, 4 figures (avaiable upon request), IFUSP/P-1086 Replaced
version: in the previous version the name of one of the authors was omitte
Conductance peaks in open quantum dots
We present a simple measure of the conductance fluctuations in open ballistic
chaotic quantum dots, extending the number of maxima method originally proposed
for the statistical analysis of compound nuclear reactions. The average number
of extreme points (maxima and minima) in the dimensionless conductance, , as
a function of an arbitrary external parameter , is directly related to the
autocorrelation function of . The parameter can be associated to an
applied gate voltage causing shape deformation in quantum dot, an external
magnetic field, the Fermi energy, etc.. The average density of maxima is found
to be , where is a universal constant
and is the conductance autocorrelation length, which is system specific.
The analysis of does not require large statistic samples,
providing a quite amenable way to access information about parametric
correlations, such as .Comment: 5 pages, 5 figures, accepted to be published - Physical Review
Letter
Hadron Production in Neutrino-Nucleon Interactions at High Energies
The multi-particle production at high energy neutrino- nucleon collisions are
investigated through the analysis of the data of the experiment CERN-WA-025 at
neutrino energy less than 260GeV and the experiments FNAL-616 and FNAL-701 at
energy range 120-250 GeV. The general features of these experiments are used as
base to build a hypothetical model that views the reaction by a Feynman diagram
of two vertices. The first of which concerns the weak interaction between the
neutrino and the quark constituents of the nucleon. At the second vertex, a
strong color field is assumed to play the role of particle production, which
depend on the momentum transferred from the first vertex. The wave function of
the nucleon quarks are determined using the variation method and relevant
boundary conditions are applied to calculate the deep inelastic cross sections
of the virtual diagram.Comment: 6 pages PDF forma
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