4,453 research outputs found
On small energy stabilization in the NLKG with a trapping potential
We consider a nonlinear Klein Gordon equation (NLKG) with short range
potential with eigenvalues and show that in the contest of complex valued
solutions the small standing waves are attractors for small solutions of the
NLKG. This extends the results already known for the nonlinear Schr\"odinger
equation and for the nonlinear Dirac equation. In addition, this extends a
result of Bambusi and Cuccagna (which in turn was an extension of a result by
Soffer and Weinstein) which considered only real valued solutions of the NLKG
Doping change and distortion effect on double-exchange ferromagnetism
Doping change and distortion effect on the double-exchange ferromagnetism are
studied within a simplified double-exchange model. The presence of distortion
is modelled by introducing the Falicov-Kimball interaction between itinerant
electrons and classical variables. By employing the dynamical mean-field theory
the charge and spin susceptibility are exactly calculated. It is found that
there is a competition between the double-exchange induced ferromagnetism and
disorder-order transition. At low temperature various long-range order phases
such as charge ordered and segregated phases coexist with ferromagnetism
depending on doping and distortion. A rich phase diagram is obtained.Comment: 8 pages, 8 figure
Linear response within the projection-based renormalization method: Many-body corrections beyond the random phase approximation
The explicit evaluation of linear response coefficients for interacting
many-particle systems still poses a considerable challenge to theoreticians. In
this work we use a novel many-particle renormalization technique, the so-called
projector-based renormalization method, to show how such coefficients can
systematically be evaluated. To demonstrate the prospects and power of our
approach we consider the dynamical wave-vector dependent spin susceptibility of
the two-dimensional Hubbard model and also determine the subsequent magnetic
phase diagram close to half-filling. We show that the superior treatment of
(Coulomb) correlation and fluctuation effects within the projector-based
renormalization method significantly improves the standard random phase
approximation results.Comment: 17 pages, 7 figures, revised versio
Temperature dependent graphene suspension due to thermal Casimir interaction
Thermal effects contributing to the Casimir interaction between objects are
usually small at room temperature and they are difficult to separate from
quantum mechanical contributions at higher temperatures. We propose that the
thermal Casimir force effect can be observed for a graphene flake suspended in
a fluid between substrates at the room temperature regime. The properly chosen
materials for the substrates and fluid induce a Casimir repulsion. The balance
with the other forces, such as gravity and buoyancy, results in a stable
temperature dependent equilibrium separation. The suspended graphene is a
promising system due to its potential for observing thermal Casimir effects at
room temperature.Comment: 5 pages, 4 figures, in APL production 201
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