2,588 research outputs found
Modelling Electron Spin Accumulation in a Metallic Nanoparticle
A model describing spin-polarized current via discrete energy levels of a
metallic nanoparticle, which has strongly asymmetric tunnel contacts to two
ferromagnetic leads, is presented.
In absence of spin-relaxation, the model leads to a spin-accumulation in the
nanoparticle, a difference () between the chemical potentials of
spin-up and spin-down electrons, proportional to the current and the Julliere's
tunnel magnetoresistance. Taking into account an energy dependent
spin-relaxation rate , as a function of bias
voltage () exhibits a crossover from linear to a much weaker dependence,
when equals the spin-polarized current through the
nanoparticle. Assuming that the spin-relaxation takes place via electron-phonon
emission and Elliot-Yafet mechanism, the model leads to a crossover from linear
to dependence. The crossover explains recent measurements of the
saturation of the spin-polarized current with in Aluminum nanoparticles,
and leads to the spin-relaxation rate of in an Aluminum
nanoparticle of diameter , for a transition with an energy difference of
one level spacing.Comment: 37 pages, 7 figure
Lax Operator for the Quantised Orthosymplectic Superalgebra U_q[osp(2|n)]
Each quantum superalgebra is a quasi-triangular Hopf superalgebra, so
contains a \textit{universal -matrix} in the tensor product algebra which
satisfies the Yang-Baxter equation. Applying the vector representation ,
which acts on the vector module , to one side of a universal -matrix
gives a Lax operator. In this paper a Lax operator is constructed for the
-type quantum superalgebras . This can in turn be used to
find a solution to the Yang-Baxter equation acting on
where is an arbitrary module. The case is included
here as an example.Comment: 15 page
Hyperbolic Kac-Moody superalgebras
We present a classification of the hyperbolic Kac-Moody (HKM) superalgebras.
The HKM superalgebras of rank larger or equal than 3 are finite in number (213)
and limited in rank (6). The Dynkin-Kac diagrams and the corresponding simple
root systems are determined. We also discuss a class of singular
sub(super)algebras obtained by a folding procedure
Performance of Wick Drains in Boston Blue Clay
The use of wick drains to accelerate the consolidation of soft clays is a cost effective alternative to the use of pile foundations. This paper presents a case history of using wick drains to accelerate the consolidation of a 5. 7 acre area in Metropolitan Boston, Massachusetts, USA. Boston Blue Clay was encountered approximately 25 to 40 ft below existing grade with varied thickness and consistency. Wick drains were installed to a depth of 70 ft in a triangular pattern. Geotechnical instruments were installed to monitor the settlement of clay with time. As a result of the preconsolidation program, about $8 million was saved in construction cost
Generalised Perk--Schultz models: solutions of the Yang-Baxter equation associated with quantised orthosymplectic superalgebras
The Perk--Schultz model may be expressed in terms of the solution of the
Yang--Baxter equation associated with the fundamental representation of the
untwisted affine extension of the general linear quantum superalgebra
, with a multiparametric co-product action as given by
Reshetikhin. Here we present analogous explicit expressions for solutions of
the Yang-Baxter equation associated with the fundamental representations of the
twisted and untwisted affine extensions of the orthosymplectic quantum
superalgebras . In this manner we obtain generalisations of the
Perk--Schultz model.Comment: 10 pages, 2 figure
Vertex Operators, Screen Currents and Correlation Functions at Arbitrary Level
Bosonized q-vertex operators related to the 4-dimensional evaluation modules
of the quantum affine superalgebra are constructed for
arbitrary level , where is a complex parameter
appearing in the 4-dimensional evaluation representations. They are
intertwiners among the level- highest weight Fock-Wakimoto modules.
Screen currents which commute with the action of up to
total differences are presented. Integral formulae for N-point functions of
type I and type II q-vertex operators are proposed.Comment: Latex file 18 page
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