46,448 research outputs found
On the tau-functions of the Degasperis-Procesi equation
The DP equation is investigated from the point of view of
determinant-pfaffian identities. The reciprocal link between the
Degasperis-Procesi (DP) equation and the pseudo 3-reduction of the
two-dimensional Toda system is used to construct the N-soliton solution of the
DP equation. The N-soliton solution of the DP equation is presented in the form
of pfaffian through a hodograph (reciprocal) transformation. The bilinear
equations, the identities between determinants and pfaffians, and the
-functions of the DP equation are obtained from the pseudo 3-reduction of
the two-dimensional Toda system.Comment: 27 pages, 4 figures, Journal of Physics A: Mathematical and
Theoretical, to be publishe
Graphitic-BN Based Metal-free Molecular Magnets From A First Principle Study
We perform a first principle calculation on the electronic properties of
carbon doped graphitic boron nitride graphitic BN. It was found that carbon
substitution for either boron or nitrogen atom in graphitic BN can induce
spontaneous magnetization. Calculations based on density functional theory with
the local spin density approximation on the electronic band structure revealed
a spin polarized, dispersionless band near the Fermi energy. Spin density
contours showed that the magnetization density originates from the carbon atom.
The magnetization can be attributed to the carbon 2p electron. Charge density
distribution shows that the carbon atom forms covalent bonds with its three
nearest neighbourhood. The spontaneous magnetization survives the curvature
effect in BN nanotubes, suggesting the possibility of molecular magnets made
from BN. Compared to other theoretical models of light-element or metal-free
magnetic materials, the carbon-doped BN are more experimentally accessible and
can be potentially useful.Comment: 8 pages, 4 figure
Generally Covariant Conservative Energy-Momentum for Gravitational Anyons
We obtain a generally covariant conservation law of energy-momentum for
gravitational anyons by the general displacement transform. The energy-momentum
currents have also superpotentials and are therefore identically conserved. It
is shown that for Deser's solution and Clement's solution, the energy vanishes.
The reasonableness of the definition of energy-momentum may be confirmed by the
solution for pure Einstein gravity which is a limit of vanishing Chern-Simons
coulping of gravitational anyons.Comment: 12 pages, Latex, no figure
Insulator-metal transition shift related to magnetic polarons in La0.67-xYxCa0.33MnO3
The magnetic transport properties have been measured for La0.67-xYxCa0.33MnO3
(0 <= x <= 0.14) system. It was found that the transition temperature Tp almost
linearly moves to higher temperature as H increases. Electron spin resonance
confirms that above Tp, there exist ferromagnetic clusters. From the magnetic
polaron point of view, the shift of Tp vs. H was understood, and it was
estimated that the size of the magnetic polaron is of 9.7~15.4 angstrom which
is consistent with the magnetic correlation length revealed by the small-angle
neutron-scattering technique. The transport properties at temperatures higher
than Tp conform to the variable-range hopping mechanism.Comment: 22 pages, 6 figures, pdf, to be published in Euro. Phys. J.
Deterministically entangling distant nitrogen-vacancy centers by a nanomechanical cantilever
We present a practical scheme by global addressing to deterministically
entangle negatively charged nitrogen-vacancy (N-V) centers in distant diamonds
using a nano-mechanical cantilever with the magnetic tips strongly coupled to
the N-V electron spins. Symmetric Dicke states are generated as an example, and
the experimental feasibility and challenge of our scheme are discussed.Comment: 5 pages, 4 figure
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