1,951 research outputs found
On the limit configuration of four species strongly competing systems
We analysed some qualitative properties of the limit configuration of the
solutions of a reaction-diffusion system of four competing species as the
competition rate tends to infinity. Large interaction induces the spatial
segregation of the species and only two limit configurations are possible:
either there is a point where four species concur, a 4-point, or there are two
points where only three species concur. We characterized, for a given datum,
the possible 4-point configuration by means of the solution of a Dirichlet
problem for the Laplace equation
On the blow-up threshold for weakly coupled nonlinear Schroedinger equations
We study the Cauchy problem for a system of two coupled nonlinear focusing
Schroedinger equations arising in nonlinear optics. We discuss when the
solutions are global in time or blow-up in finite time. Some results, in
dependence of the data of the problem, are proved; in particular we give a
bound, depending on the coupling parameter, for the blow-up threshold.Comment: 14 page
Semiclassical states for weakly coupled nonlinear Schr\"odinger systems
We consider systems of weakly coupled Schr\"odinger equations with
nonconstant potentials and we investigate the existence of nontrivial
nonnegative solutions which concentrate around local minima of the potentials.
We obtain sufficient and necessary conditions for a sequence of least energy
solutions to concentrate.Comment: 23 pages, no figure
Fractional diffusion with Neumann boundary conditions: the logistic equation
Motivated by experimental studies on the anomalous diffusion of biological
populations, we introduce a nonlocal differential operator which can be
interpreted as the spectral square root of the Laplacian in bounded domains
with Neumann homogeneous boundary conditions. Moreover, we study related linear
and nonlinear problems exploiting a local realization of such operator as
performed in [X. Cabre' and J. Tan. Positive solutions of nonlinear problems
involving the square root of the Laplacian. Adv. Math. 2010] for Dirichlet
homogeneous data. In particular we tackle a class of nonautonomous
nonlinearities of logistic type, proving some existence and uniqueness results
for positive solutions by means of variational methods and bifurcation theory.Comment: 36 pages, 1 figur
On the logarithmic Schrodinger equation
In the framework of the nonsmooth critical point theory for lower
semi-continuous functionals, we propose a direct variational approach to
investigate the existence of infinitely many weak solutions for a class of
semi-linear elliptic equations with logarithmic nonlinearity arising in
physically relevant situations. Furthermore, we prove that there exists a
unique positive solution which is radially symmetric and nondegenerate.Comment: 10 page
A Dirichlet problem in the strip
In this paper we investigate a Dirichlet problem in a strip and, using the sliding method, we prove monotonicity for positive and bounded solutions. We obtain uniqueness of the solution and show that this solution is a function of only one variable. From these qualitative properties we deduce existence of a classical solution for this problem
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