967,953 research outputs found
A note on the Zassenhaus product formula
We provide a simple method for the calculation of the terms c_n in the
Zassenhaus product for
non-commuting a and b. This method has been implemented in a computer program.
Furthermore, we formulate a conjecture on how to translate these results into
nested commutators. This conjecture was checked up to order n=17 using a
computer
Higgs and Z boson associated production via gluon fusion in the SM and the 2HDM
We analyse the associated production of Higgs and boson via heavy-quark
loops at the LHC in the Standard Model and beyond. We first review the main
features of the Born production, and in particular discuss the
high-energy behaviour, angular distributions and boson polarisation. We
then consider the effects of extra QCD radiation as described by the
loop matrix elements, and find that they dominate at high Higgs transverse
momentum. We show how merged samples of 0-- and 1--jet multiplicities, matched
to a parton shower can provide a reliable description of differential
distributions in production. In addition to the Standard Model study,
results in a generic two-Higgs-doublet-model are obtained and presented for a
set of representative and experimentally viable benchmarks for ,
and production. We observe that various interesting features appear
either due to the resonant enhancement of the cross-section or to interference
patterns between resonant and non-resonant contributions.Comment: 29 pages, 12 figure
Parity oscillations of Kondo temperature in a single molecule break junction
We study the Kondo temperature () of a single molecule break junction.
By employing a numerical renormalization group calculations we have found that
depends dramatically upon the position of the molecule in the wire formed
between the contacts. We show that exhibits strong \emph{oscillations}
when the parity of the left {and/or} right number of atomic sites ()
is changed. For a given set of parameters, the maximum value of occurs
for () combination, while its minimum values is observed for
().
These oscillations are fully understood in terms of the effective
hybridization function.Comment: 4 pages, 5 figure
Theory and computation of electromagnetic fields and thermomechanical structure interaction for systems undergoing large deformations
For an accurate description of electromagneto-thermomechanical systems,
electromagnetic fields need to be described in a Eulerian frame, whereby the
thermomechanics is solved in a Lagrangean frame. It is possible to map the
Eulerian frame to the current placement of the matter and the Lagrangean frame
to a reference placement. We present a rigorous and thermodynamically
consistent derivation of governing equations for fully coupled
electromagneto-thermomechanical systems properly handling finite deformations.
A clear separation of the different frames is necessary. There are various
attempts to formulate electromagnetism in the Lagrangean frame, or even to
compute all fields in the current placement. Both formulations are challenging
and heavily discussed in the literature. In this work, we propose another
solution scheme that exploits the capabilities of advanced computational tools.
Instead of amending the formulation, we can solve thermomechanics in the
Lagrangean frame and electromagnetism in the Eulerian frame and manage the
interaction between the fields. The approach is similar to its analog in fluid
structure interaction, but more challenging because the field equations in
electromagnetism must also be solved within the solid body while following
their own different set of transformation rules. We additionally present a
mesh-morphing algorithm necessary to accommodate finite deformations to solve
the electromagnetic fields outside of the material body. We illustrate the use
of the new formulation by developing an open-source implementation using the
FEniCS package and applying this implementation to several engineering problems
in electromagnetic structure interaction undergoing large deformations
Matching Conditions in Atomistic-Continuum Modeling of Materials
A new class of matching condition between the atomistic and continuum regions
is presented for the multi-scale modeling of crystals. They ensure the accurate
passage of large scale information between the atomistic and continuum regions
and at the same time minimize the reflection of phonons at the interface. These
matching conditions can be made adaptive if we choose appropriate weight
functions. Applications to dislocation dynamics and friction between
two-dimensional atomically flat crystal surfaces are described.Comment: 6 pages, 4 figure
Summary of electric vehicle dc motor-controller tests
The differences in the performance of dc motors are evaluated when operating with chopper type controllers, and when operating on direct current. The interactions between the motor and the controller which cause these differences are investigated. Motor-controlled tests provided some of the data the quantified motor efficiency variations for both ripple free and chopper modes of operation
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