7,988 research outputs found
An analytically solvable model of probabilistic network dynamics
We present a simple model of network dynamics that can be solved analytically
for uniform networks. We obtain the dynamics of response of the system to
perturbations. The analytical solution is an excellent approximation for random
networks. A comparison with the scale-free network, though qualitatively
similar, shows the effect of distinct topology.Comment: 4 pages, 1 figur
Chaos in one-dimensional lattices under intense laser fields
A model is investigated where a monochromatic, spatially homogeneous laser
field interacts with an electron in a one-dimensional periodic lattice. The
classical Hamiltonian is presented and the technique of stroboscopic maps is
used to study the dynamical behavior of the model. The electron motion is found
to be completely regular only for small field amplitudes, developing a larger
chaotic region as the amplitude increases. The quantum counterpart of the
classical Hamiltonian is derived. Exact numerical diagonalizations show the
existence of universal, random-matrix fluctuations in the electronic energy
bands dressed by the laser field. A detailed analysis of the classical phase
space is compatible with the statistical spectral analysis of the quantum
model. The application of this model to describe transport and optical
absorption in semiconductor superlattices submitted to intense infrared laser
radiation is proposed.Comment: 9 pages, RevTex 3.0, EPSF (6 figures), to appear in Europhys. J.
Kondo effect in transport through molecules adsorbed on metal surfaces: from Fano dips to Kondo peaks
The Kondo effect observed in recent STM experiments on transport through CoPc
and TBrPP-Co molecules adsorbed on Au(111) and Cu(111) surfaces, respectively,
is discussed within the framework of a simple model (Phys. Rev. Lett. {\bf 97},
076806 (2006)). It is shown that, in the Kondo regime and by varying the
adequate model parameters, it is possible to produce a crossover from a
conductance Kondo peak (CoPc) to a conductance Fano dip (TBrPP-Co). In the case
of TBrPP-Co/Cu(111) we show that the model reproduces the changes in the shape
of the Fano dip, the raising of the Kondo temperature and shifting to higher
energies of the dip minimum when the number of nearest neighbors molecules is
lowered. These features are in line with experimental observations indicating
that our simple model contains the essential physics underlying the transport
properties of such complex molecules.Comment: 4 pages, 3 figures, submitted to PR
Distinct magnetic signatures of fractional vortex configurations in multiband superconductors
Vortices carrying fractions of a flux quantum are predicted to exist in
multiband superconductors, where vortex core can split between multiple
band-specific components of the superconducting condensate. Using the
two-component Ginzburg-Landau model, we examine such vortex configurations in a
two-band superconducting slab in parallel magnetic field. The fractional
vortices appear due to the band-selective vortex penetration caused by
different thresholds for vortex entry within each band-condensate, and
stabilize near the edges of the sample. We show that the resulting fractional
vortex configurations leave distinct fingerprints in the static measurements of
the magnetization, as well as in ac dynamic measurements of the magnetic
susceptibility, both of which can be readily used for the detection of these
fascinating vortex states in several existing multiband superconductors.Comment: 5 pages, 4 figure
Energy transfer dynamics and thermalization of two oscillators interacting via chaos
We consider the classical dynamics of two particles moving in harmonic
potential wells and interacting with the same external environment (HE),
consisting of N non-interacting chaotic systems. The parameters are set so that
when either particle is separately placed in contact with the environment, a
dissipative behavior is observed. When both particles are simultaneously in
contact with HE an indirect coupling between them is observed only if the
particles are in near resonance. We study the equilibrium properties of the
system considering ensemble averages for the case N=1 and single trajectory
dynamics for N large. In both cases, the particles and the environment reach an
equilibrium configuration at long times, but only for large N a temperature can
be assigned to the system.Comment: 8 pages, 6 figure
The Tchebyshev transforms of the first and second kind
We give an in-depth study of the Tchebyshev transforms of the first and
second kind of a poset, recently discovered by Hetyei. The Tchebyshev transform
(of the first kind) preserves desirable combinatorial properties, including
Eulerianess (due to Hetyei) and EL-shellability. It is also a linear
transformation on flag vectors. When restricted to Eulerian posets, it
corresponds to the Billera, Ehrenborg and Readdy omega map of oriented
matroids. One consequence is that nonnegativity of the cd-index is maintained.
The Tchebyshev transform of the second kind is a Hopf algebra endomorphism on
the space of quasisymmetric functions QSym. It coincides with Stembridge's peak
enumerator for Eulerian posets, but differs for general posets. The complete
spectrum is determined, generalizing work of Billera, Hsiao and van
Willigenburg.
The type B quasisymmetric function of a poset is introduced. Like Ehrenborg's
classical quasisymmetric function of a poset, this map is a comodule morphism
with respect to the quasisymmetric functions QSym.
Similarities among the omega map, Ehrenborg's r-signed Birkhoff transform,
and the Tchebyshev transforms motivate a general study of chain maps. One such
occurrence, the chain map of the second kind, is a Hopf algebra endomorphism on
the quasisymmetric functions QSym and is an instance of Aguiar, Bergeron and
Sottile's result on the terminal object in the category of combinatorial Hopf
algebras. In contrast, the chain map of the first kind is both an algebra map
and a comodule endomorphism on the type B quasisymmetric functions BQSym.Comment: 33 page
Analysis of structure withdissipator spectra under design and control
Las estructuras de Quito, Ecuador, son diseñadas para el espectro de la norma ecuatoriana de 2015, o para el hallado en la microzonificación de la ciudad de 2012. Estos espectros consideran en forma macro las fallas ciegas inversas sobre las que se halla la ciudad. En este artÃculo se destaca la importancia de verificar el diseño para los espectros de control que fueron desarrollados mediante métodos determinÃsticos para Quito en el 2015, los mismos que consideran la generación de sismos en las fallas ciegas.
En el artÃculo se presentan dos modelos de plasticidad extendida para los elementos estructurales y un modelo de plasticidad para los disipadores ADAS o TADAS. Luego se indica con cierto detalle la técnica del pushover multimodal y el método del espectro de capacidad con el cual se halla el punto de capacidad de una estructura que fue inicialmente calculada para los espectros de diseño. Dicha estructura ha sido reforzada con disipadores ADAS para que no colapse ante el espectro de control que tiene ordenadas más altas que el espectro de diseño.The structures of Quito, Ecuador, are designed for the spectrum of the Ecuadorian code of 2015, or using the study of microzoning of the city of 2012. These spectra consider in general the effect of the blind reverse faults belonging to the city area. In this article, it is pointed out the importance of checking the design for the deterministic control spectra developed for Quito in 2015 based on earthquakes simulated in the blinds faults.
In this paper we considered two models of extended plasticity for the structural elements and one model of plasticity for the ADAS and TADAS devices. Then, the technique of multimodal pushover is described, as well as the method of the capacity spectrum used to calculate the performance point of the structure. This structure was initially calculated by using design spectra and it had to be reinforced with ADAS devices in order to avoid its collapse for the control spectrum which has higher ordinates than the design one.Peer Reviewe
A conjugate for the Bargmann representation
In the Bargmann representation of quantum mechanics, physical states are
mapped into entire functions of a complex variable z*, whereas the creation and
annihilation operators and play the role of
multiplication and differentiation with respect to z*, respectively. In this
paper we propose an alternative representation of quantum states, conjugate to
the Bargmann representation, where the roles of and
are reversed, much like the roles of the position and momentum operators in
their respective representations. We derive expressions for the inner product
that maintain the usual notion of distance between states in the Hilbert space.
Applications to simple systems and to the calculation of semiclassical
propagators are presented.Comment: 15 page
Quantum Dissipation and Decoherence via Interaction with Low-Dimensional Chaos: a Feynman-Vernon Approach
We study the effects of dissipation and decoherence induced on a harmonic
oscillator by the coupling to a chaotic system with two degrees of freedom.
Using the Feynman-Vernon approach and treating the chaotic system
semiclassically we show that the effects of the low dimensional chaotic
environment are in many ways similar to those produced by thermal baths. The
classical correlation and response functions play important roles in both
classical and quantum formulations. Our results are qualitatively similar to
the high temperature regime of the Caldeira-Leggett model.Comment: 31 pages, 4 figure
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