3,759 research outputs found
Extended coherent states and modified perturbation theory
An extended coherent state for describing a system of two interacting quanum
objects is considered. A modified perturbation theory based on using the
extended coherent states is formulated.Comment: LaTex, 7 pages, no figures, minor correction
Algebraic Model for scattering in three-s-cluster systems. I. Theoretical Background
A framework to calculate two-particle matrix elements for fully
antisymmetrized three-cluster configurations is presented. The theory is
developed for a scattering situation described in terms of the Algebraic Model.
This means that the nuclear many-particle state and its asymptotic behaviour
are expanded in terms of oscillator states of the intra-cluster coordinates.
The Generating Function technique is used to optimize the calculation of matrix
elements. In order to derive the dynamical equations, a multichannel version of
the Algebraic Model is presented.Comment: 20 pages, 1 postscript figure, submitted to Phys. Rev.
Peculiar properties of the cluster-cluster interaction induced by the Pauli exclusion principle
Role of the Pauli principle in the formation of both the discrete spectrum
and multi-channel states of the binary nuclear systems composed of clusters is
studied in the Algebraic Version of the resonating-group method. Solutions of
the Hill-Wheeler equations in the discrete representation of a complete basis
of the Pauli-allowed states are discussed for 4He+n, 3H+3H, and 4He+4He binary
systems. An exact treatment of the antisymmetrization effects are shown to
result in either an effective repulsion of the clusters, or their effective
attraction. It also yields a change in the intensity of the centrifugal
potential. Both factors significantly affect the scattering phase behavior.
Special attention is paid to the multi-channel cluster structure 6He+6He as
well as to the difficulties arising in the case when the two clustering
configurations, 6He+6He and 4He+8He, are taken into account simultaneously. In
the latter case the Pauli principle, even in the absence of a potential energy
of the cluster-cluster interaction, leads to the inelastic processes and
secures an existence of both the bound state and resonance in the 12Be compound
nucleus.Comment: 17 pages, 14 figures, 1 table; submitted to Phys.Rev.C Keywords:
light neutron-rich nuclei, cluster model
Manipulations of individual molecules by scanning probe microscopy
In this Letter we suggest a new method of manipulating individual molecules
with scanning probes using a "pick-up-and put-down" mode. We demonstrate that
the number of molecules picked up by the tip and deposited in a different
location can be controlled by adjusting the pulling velocity of the tip and the
distance of closest approach of the tip to the surface
Fractal-like aggregates: Relation between morphology and physical properties
A number of modern technological applications require a detailed
calculation of the physical properties of aggregated aerosol particles. For example, in probing soot aerosols by the method called
laser-induced incandescence (LII), the soot clusters are suddenly
heated by a short, powerful laser pulse and then cool down to the
temperature of the carrier gas. LII sizing is based on rigorous calculation of the soot aggregate heat-up and cooling and involves
prediction of laser light absorption and energy and mass transfer between aggregated particles and the ambient gas. This paper
describes results of numerical simulations of the mass or energy
transfer between the gas and fractal-like aggregates of N spherical
particles in either the free-molecular or continuum regime, as well
as the light scattering properties of random fractal-like aggregates,
based on Rayleigh–Debye–Gans (RDG) theory. The aggregate geometries are generated numerically using specially developed algorithms allowing “tuning” of the fractal dimension and prefactor
values. Our results are presented in the form of easily applicable
scaling laws, with special attention paid to relations between the
aggregate gyration radius and the effective radius describing various transport processes between the aggregates and the carrier gas
Buckling Analysis of Axially Compressed Square Elastic Tubes with Weakly Supported Edges
The local buckling of weakly supported thin-walled square tubes under axial compression is studied. By means of asymptotic methods, an expression for the critical pressure is found. The asymptotic results agree well with the numerical results obtained with the Finite Element Method (FEM) and with the sweepmethod. The dependence of the critical loading on the shell length and on the type of edge supporting is analyzed
Simulation of indivisible qubit channels in collision models
A sequence of controlled collisions between a quantum system and its
environment (composed of a set of quantum objects) naturally simulates (with
arbitrary precision) any Markovian quantum dynamics of the system under
consideration. In this paper we propose and study the problem of simulation of
an {\it arbitrary} quantum channel via collision models. We show that a
correlated environment is capable to simulate {\it non-Markovian} evolutions
leading to any indivisible qubit channel. In particular, we derive the
corresponding master equation generating a continuous time non-Markovian
dynamics implementing the universal NOT gate being an example of the most
non-Markovian quantum channels.Comment: 6 pages, 2 figures, submitted to JP
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