19,478 research outputs found
The energy dependence of the amplitude and the three-nucleon interaction
By calculating the contribution of the three-body force to the
three-nucleon binding energy in terms of the amplitude using
perturbation theory, we are able to determine the importance of the energy
dependence and the contribution of the different partial waves of the
amplitude to the three-nucleon force. A separable representation of the
non-pole amplitude allows us to write the three-nucleon force in terms
of the amplitude for , propagation of the system,
and the amplitude for , with being the
quasi-particle amplitude in a given state. The division of the
amplitude into a pole and non-pole gives a procedure for the determination of
the form factor within the model. The total contribution of the
three-body force to the binding energy of the triton for the separable
approximation to the Paris nucleon-nucleon potential (PEST) is found to be very
small mainly as a result of the energy dependence of the amplitude, the
cancellation between the - and -wave amplitudes, and the soft
form factor.Comment: RevTex file, 36 pages, 10 figures available from authors:
[email protected]
Degeneracy breaking and intervalley scattering due to short-ranged impurities in finite single-wall carbon nanotubes
We present a theoretical study of degeneracy breaking due to short-ranged
impurities in finite, single-wall, metallic carbon nanotubes. The effective
mass model is used to describe the slowly varying spatial envelope
wavefunctions of spinless electrons near the Fermi level at two inequivalent
valleys (K-points) in terms of the four component Dirac equation for massless
fermions, with the role of spin assumed by pseudospin due to the relative
amplitude of the wave function on the sublattice atoms (``A'' and ``B''). Using
boundary conditions at the ends of the tube that neither break valley
degeneracy nor mix pseudospin eigenvectors, we use degenerate perturbation
theory to show that the presence of impurities has two effects. Firstly, the
position of the impurity with respect to the spatial variation of the envelope
standing waves results in a sinusoidal oscillation of energy level shift as a
function of energy. Secondly, the position of the impurity within the hexagonal
graphite unit cell produces a particular 4 by 4 matrix structure of the
corresponding effective Hamiltonian. The symmetry of this Hamiltonian with
respect to pseudospin flip is related to degeneracy breaking and, for an
armchair tube, the symmetry with respect to mirror reflection in the nanotube
axis is related to pseudospin mixing.Comment: 20 pages, 10 eps figure
Coupled ion - nanomechanical systems
We study ions in a nanotrap, where the electrodes are nanomechanical
resonantors. The ions play the role of a quantum optical system which acts as a
probe and control, and allows entanglement with or between nanomechanical
resonators.Comment: 4 pages, 2 figures, submitted for publicatio
Phase mixing of shear Alfvén waves as a new mechanism for electron acceleration in collisionless, kinetic plasmas
Particle-in-cell (kinetic) simulations of shear Alfv´en wave (AW) interaction with one-dimensional, across the uniform-magnetic field, density inhomogeneity (phase mixing) in collisionless plasma were performed for the first time. As a result, a new electron acceleration mechanism is discovered. Progressive distortion of the AW front, due to the differences in local Alfv´en speed, generates electrostatic fields nearly parallel to the magnetic field, which accelerate electrons via Landau damping. Surprisingly, the amplitude decay law in the inhomogeneous regions, in the kinetic regime, is the same as in the MHD approximation described by Heyvaerts and Priest (1983 Astron. Astrophys. 117 220)
Chirality Selection in Open Flow Systems and in Polymerization
As an attempt to understand the homochirality of organic molecules in life, a
chemical reaction model is proposed where the production of chiral monomers
from achiral substrate is catalyzed by the polymers of the same enatiomeric
type. This system has to be open because in a closed system the enhanced
production of chiral monomers by enzymes is compensated by the associated
enhancement in back reaction, and the chiral symmetry is conserved. Open flow
without cross inhibition is shown to lead to the chirality selection in a
general model. In polymerization, the influx of substrate from the ambience and
the efflux of chiral products for purposes other than the catalyst production
make the system necessarily open. The chiral symmetry is found to be broken if
the influx of substrate lies within a finite interval. As the efficiency of the
enzyme increases, the maximum value of the enantiomeric excess approaches unity
so that the chirality selection becomes complete.Comment: 8 pages, 4 figure
Disturbances of both cometary and Earth's magnetospheres excited by single solar flares
In the solar wind a comet plays the role of a windvane that moves three-dimensionally in the heliomagnetosphere. Among the solar systems bodies, only comets have a wide range of inclination angles of their orbital planes to the ecliptic plane ranging from 0 to 90 deg. Therefore, observations of cometary plasma tails are useful in probing the heliomagnetospheric conditions in the high heliolatitudinal region. A comet can be compared to a polar-orbiting probe encircling the Sun. We will introduce two rare cases in which the magnetospheres of both the comet and the Earth are disturbed by a single solar flare
Gap opening in graphene by simple periodic inhomogeneous strain
Using ab-initio methods, we show that the uniform deformation either leaves
graphene (semi)metallic or opens up a small gap yet only beyond the mechanical
breaking point of the graphene, contrary to claims in the literature based on
tight-binding (TB) calculations. It is possible, however, to open up a global
gap by a sine-like one-dimensional inhomogeneous deformation applied along any
direction but the armchair one, with the largest gap for the corrugation along
the zigzag direction (~0.5 eV) without any electrostatic gating. The gap
opening has a threshold character with very sharp rise when the ratio of the
amplitude A and the period of the sine wave deformation lambda exceeds
(A/lambda)_c ~0.1 and the inversion symmetry is preserved, while it is
threshold-less when the symmetry is broken, in contrast with TB-derived
pseudo-magnetic field models.Comment: 6 pages, 6 figures; (v2) added figures illustrating opening gap in
Graphene mesh on BN, expanded analysis illustrating absence of
pseudo-magnetic fields in deformed Graphen
Calculation of the Self-energy of Open Quantum Systems
We propose an easy method of calculating the self-energy of semi-infinite
leads attached to a mesoscopic system.Comment: 6 pages, 2 figures, published in J. Phys. Soc. Jp
Divine Adoption in the Confessions of the Reformation Period
Boer, E.A. de [Promotor]Vlastuin, W. van [Copromotor
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