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Positive solutions with given slope of a nonlocal second order boundary value problem with sign changing nonlinearities

P. Ch. Tsamatos (2004)

Annales Polonici Mathematici

We study a nonlocal boundary value problem for the equation x''(t) + f(t,x(t),x'(t)) = 0, t ∈ [0,1]. By applying fixed point theorems on appropriate cones, we prove that this boundary value problem admits positive solutions with slope in a given annulus. It is remarkable that we do not assume f≥0. Here the sign of the function f may change.

Properties of the set of positive solutions to Dirichlet boundary value problems with time singularities

Irena Rachůnková, Svatoslav Staněk (2013)

Open Mathematics

The paper investigates the structure and properties of the set S of all positive solutions to the singular Dirichlet boundary value problem u″(t) + au′(t)/t − au(t)/t 2 = f(t, u(t),u′(t)), u(0) = 0, u(T) = 0. Here a ∈ (−∞,−1) and f satisfies the local Carathéodory conditions on [0,T]×D, where D = [0,∞)×ℝ. It is shown that S c = {u ∈ S: u′(T) = −c} is nonempty and compact for each c ≥ 0 and S = ∪c≥0 S c. The uniqueness of the problem is discussed. Having a special case of the problem, we introduce...

Semiclassical states for weakly coupled nonlinear Schrödinger systems

Eugenio Montefusco, Benedetta Pellacci, Marco Squassina (2008)

Journal of the European Mathematical Society

We consider systems of weakly coupled Schrödinger equations with nonconstant potentials and 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.

Singular nonlinear problem for ordinary differential equation of the second order

Irena Rachůnková, Jan Tomeček (2007)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

The paper deals with the singular nonlinear problem u ' ' ( t ) + f ( t , u ( t ) , u ' ( t ) ) = 0 , u ( 0 ) = 0 , u ' ( T ) = ψ ( u ( T ) ) , where f 𝐶𝑎𝑟 ( ( 0 , T ) × D ) , D = ( 0 , ) × . We prove the existence of a solution to this problem which is positive on ( 0 , T ] under the assumption that the function f ( t , x , y ) is nonnegative and can have time singularities at t = 0 , t = T and space singularity at x = 0 . The proof is based on the Schauder fixed point theorem and on the method of a priori estimates.

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