7,689 research outputs found
Magnetotransport in the low carrier density ferromagnet EuB_6
We present a magnetotransport study of the low--carrier density ferromagnet
EuB_6. This semimetallic compound, which undergoes two ferromagnetic
transitions at T_l = 15.3 K and T_c = 12.5 K, exhibits close to T_l a colossal
magnetoresistivity (CMR). We quantitatively compare our data to recent
theoretical work, which however fails to explain our observations. We attribute
this disagreement with theory to the unique type of magnetic polaron formation
in EuB_6.Comment: Conference contribution MMM'99, San Jos
A Variational Principle for the Asymptotic Speed of Fronts of the Density Dependent Diffusion--Reaction Equation
We show that the minimal speed for the existence of monotonic fronts of the
equation with , and in
derives from a variational principle. The variational principle allows
to calculate, in principle, the exact speed for arbitrary . The case
when is included as an extension of the results.Comment: Latex, postcript figure availabl
Self-Similar Solutions to a Density-Dependent Reaction-Diffusion Model
In this paper, we investigated a density-dependent reaction-diffusion
equation, . This equation is known as the
extension of the Fisher or Kolmogoroff-Petrovsky-Piscounoff equation which is
widely used in the population dynamics, combustion theory and plasma physics.
By employing the suitable transformation, this equation was mapped to the
anomalous diffusion equation where the nonlinear reaction term was eliminated.
Due to its simpler form, some exact self-similar solutions with the compact
support have been obtained. The solutions, evolving from an initial state,
converge to the usual traveling wave at a certain transition time. Hence, it is
quite clear the connection between the self-similar solution and the traveling
wave solution from these results. Moreover, the solutions were found in the
manner that either propagates to the right or propagates to the left.
Furthermore, the two solutions form a symmetric solution, expanding in both
directions. The application on the spatiotemporal pattern formation in
biological population has been mainly focused.Comment: 5 pages, 2 figures, accepted by Phys. Rev.
Relaxation under outflow dynamics with random sequential updating
In this paper we compare the relaxation in several versions of the Sznajd
model (SM) with random sequential updating on the chain and square lattice. We
start by reviewing briefly all proposed one dimensional versions of SM. Next,
we compare the results obtained from Monte Carlo simulations with the mean
field results obtained by Slanina and Lavicka . Finally, we investigate the
relaxation on the square lattice and compare two generalizations of SM, one
suggested by Stauffer and another by Galam. We show that there are no
qualitative differences between these two approaches, although the relaxation
within the Galam rule is faster than within the well known Stauffer rule.Comment: 9 figure
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