Vol. 43, No. 1           March 2014


Title and Author(s) Page
item Caratheodory convex selections of set-valued functions in Banach lattices
Jerzy Motyl
ABSTRACT. Let $T$ be a measurable space, $X$ a Banach space while $Y$ a Banach lattice. We consider the class of ``upper separated'' set-valued functions $F\colon T\times X \rightarrow 2^{Y}$ and investigate the problem of the existence of Carath\'eodory type selection, that is, measurable in the first variable and order-convex in the second variable.
item Existence of positive solutions for a second order periodic boundary value problem with impulsive effects
Jiafa Xu, Zhongli Wei and Youzheng Ding
ABSTRACT. In this paper, we are mainly concerned with the existence and multiplicity of positive solutions for the following second order periodic boundary value problem involving impulsive effects
\cases -u''+\rho^2u=f(t,u), & t\in J',\\ -\Delta u'|_{t=t_k}=I_k(u(t_k)), & k=1,\ldots,m,
u(0)-u(2\pi)=0,\quad u'(0)-u'(2\pi)=0. \endcases
Here $J'=J\setminus \{t_1,\ldots, t_m\}$, $f\in C(J\times \Bbb R^+, \Bbb R^+)$, $I_k\in C( \Bbb R^+, \Bbb R^+)$, where $ \Bbb R^+=[0,\infty)$, $J=[0,2\pi]$. The proof of our main results relies on the fixed point theorem on cones. The paper extends some previous results and reports some new results about impulsive differential equations.
item Generalizations of Krasnoselskii's fixed point theorem in cones and applications
Sorin Budisan
ABSTRACT. We give some generalizations of Krasnosel'ski{\u\i}'s fixed point theorem in cones, replacing norms with functionals. We will apply these theorems to obtain at least one positive solution for the boundary value problems for second-order differential equations. Two positive solution results are also obtained.
item Heteroclinics for some non autonomous third order differential equations
Denis Bonheure, Jose Angel Cid, Colette De Coster and Luis Sanchez
ABSTRACT. We study the existence of heteroclinics connecting the two equilibria $\pm1$ of the third order differential equation
where $f$ is a continuous function such that $f(u)(u^2-1)>0$ if $u\neq\pm1$ and $p$ is a bounded non negative function. Uniqueness is also addressed.
item Weighted pseudo almost automorphic solutions to nonautonomous semilinear evolution equations with delay and $S^p$-weighted pseudo almost automorphic coefficients
Yong-Kui Chang, Rui Zhang and G. M. N'Guerekata
ABSTRACT. By some new properties of Stepanov-like weighted pseudo almost automorphic functions established by Chang, Zhang and N'Gu\'{e}r\'{e}kata recently, we shall deal with weighted pseudo almost automorphic solutions to the nonautonomous semilinear evolution equations with a constant delay: $u'(t)=A(t)u(t)+f(t,u(t-h))$, $ t\in\mathbb{R}$ in a Banach space $\mathbb{X}$, where $A(t),t\in\mathbb{R}$ generates an exponentially stable evolution family $\{U(t,s)\}$ and $f \colon\mathbb{R}\times\mathbb{X} \rightarrow \mathbb{X}$ is a $\S^{p}$-weighted pseudo almost automorphic function satisfying some suitable conditions. We obtain our main results by the Leray-Shauder Alternative theorem.
item Holder continuous retractions and amenable semigroups of uniformly Lipschitzian mappings in Hilbert spaces
Andrzej Wisnicki
ABSTRACT. Suppose that $S$ is a left amenable semitopological semigroup. We prove that if $\mathcal{S}=\{ T_{t}:t\in S\} $ is a uniformly $k$-Lipschitzian semigroup on a bounded closed and convex subset $C$ of a Hilbert space and $k<\sqrt{2}$, then the set of fixed points of $\mathcal{S}$ is a H\"{o}lder continuous retract of $C$. This gives a qualitative complement to the Ishihara-Takahashi fixed point existence theorem.
item Limit sets in impulsive semidynamical systems
Changming Ding
ABSTRACT. In this paper, we establish several fundamental properties in impulsive semidynamical systems. First, we formulate a counterpart of the continuous dependence on the initial conditions for impulsive dynamical systems, and also establish some equivalent properties. Second, we present several theorems similar to the Poincar\'e-Bendixson theorem for two-dimensional impulsive systems, i.e\. if the omega limit set of a bounded infinite trajectory (with an infinite number of impulses) contains no rest points, then there exists an almost recurrent orbit in the limit set. Further, if the omega limit set contains an interior point, then it is a chaotic set; otherwise, if the limit set contains no interior points, then the limit set contains a periodic orbit or a Cantor-type minimal set in which each orbit is almost recurrent.
item A criterion for bijectivity of mappings of euclidean spaces
Albeta Mafra and Marcelo Tavares
ABSTRACT. We study the following problem introduced by J. Hadamard in 1906: to find sufficient conditions for a local diffeomorphism of an Euclidean space to be a global diffeomorphism. J. Hadamard introduced a celebrated integral condition which is a sufficient condition for the bijectivity of a local diffeomorphism. In this paper we improve the classical result of Hadamard giving a new sufficient condition for a $C^2$ mapping to be bijective.
item Existence of periodic traveling-wave solutions for a nonlinear Schrodinger system: A topological approach
Nghiem V. Nguyen
ABSTRACT. In this paper, the existence of periodic traveling-wave solutions for a nonlinear Schr\"odinger system is established using the topological degree theory for positive operators. The method guarantees existence of periodic solutions in a parameter region in the period and phase speed plane.
item Existence of periodic solutions for some singular elliptic equations with strong resonant data
Laura Gonella
ABSTRACT. We prove the existence of at least one $T$-periodic solution $(T\nobreak>\nobreak0)$ for differential equations of the form
\left(\frac{u'(t)}{\sqrt{1-{u'}^2(t)}}\right)' =f(u(t))+h(t),\quad \text{in } (0,T),
where $f$ is a continuous function defined on $\mathbb{R}$ that satisfies a {\it strong resonance condition}, $h$ is continuous and with zero mean value. Our method uses variational techniques for nonsmooth functionals.
item Conley index orientations
Axel Janig
ABSTRACT. The homotopy Conley index along heteroclinic solutions of certain parabolic evolution equations is zero under appropriate assumptions. This result implies that the so-called connecting homomorphism associated with a heteroclinic solution is an isomorphism. Hence, using $\IZ$-coefficients it can be viewed as either $1$ or $-1$ - depending on the choice of generators for the homology Conley index. We develop a method to choose such generators, and compute the connecting homomorphism relative to these generators.
item Properness and topological degree for nonlocal integro-differential systems
Narcisia C. Apreutesei and Vitaly A. Volpert
ABSTRACT. Reaction-diffusion systems of equations with integral terms are studied. Essential spectrum of the corresponding linear operators is determined and the Fredholm property is studied. Properness of nonlinear operators is proved and topological degree is constructed.
item Lyapunov functions, shadowing and topological stability
Alexey A. Petrov and Sergei Yu. Pilyugin
ABSTRACT. We use Lyapunov type functions to give new conditions under which a homeomorphism of a compact metric space has the shadowing property. These conditions are applied to establish the topological stability of some homeomorphisms with nonhyperbolic behavior.
item A relaxed Halpern's type iteration for an infinite family of nonexpansive mappings in CAT(0) spaces
Wei-Qi Deng
ABSTRACT. Under weaker conditions on parameters, we prove strong convergence theorems of Halpern type iteration schemes for sequences of nonexpansive mappings in CAT(0) spaces. Since there is no assumption of the AKTT-condition imposed on the involved mappings, the results improve those of the authors with related researches.
item A critica fractional Laplace equation in the resonant case
Raffaella Servadei
ABSTRACT. In this paper we complete the study of the following non-local fractional equation involving critical nonlinearities
\cases (-\Delta)^s u-\lambda u=|u|^{2^*-2}u & {\text{in }} \Omega,
u=0 & {\text{in }} \RR^n\setminus \Omega, \endcases
started in the recent papers \cite{13}, \cite{17}-\cite{19}. Here $s\in (0,1)$ is a fixed parameter, $(-\Delta )^s$ is the fractional Laplace operator, $\lambda$ is a positive constant, $2^*=2n/(n-2s)$ is the fractional critical Sobolev exponent and $\Omega$ is an open bounded subset of $\RR^n$, $n>2s$, with Lipschitz boundary. Aim of this paper is to study this critical problem in the special case when $n\not=4s$ and $\lambda$ is an eigenvalue of the operator $(-\Delta)^s$ with homogeneous Dirichlet boundary datum. In this setting we prove that this problem admits a non-trivial solution, so that with the results obtained in \cite{13}, \cite{17}-\cite{19}, we are able to show that this critical problem admits a nontrivial solution provided
  • $n>4s$ and $\lambda>0$,
  • $n=4s$ and $\lambda>0$ is different from the eigenvalues of $(-\Delta)^s$,
  • $2s0$ is sufficiently large.
In this way we extend completely the famous result of Brezis and Nirenberg (see \cite{4}, \cite{5}, \cite{9}, \cite{23}) for the critical Laplace equation to the non-local setting of the fractional Laplace equation.
item Radial symmetry of n-mode positive solutions for semilinear elliptic equations in a disc and its application to the Henon equation
Naoki Shioji and Kohtaro Watanabe
ABSTRACT. Let $f \in C((0,1)\times (0,\infty),\R)$ and $n \in \N$ with $n \geq 2$ such that for each $u \in (0,\infty)$, $r\mapsto r^{2-2n}f(r,u)\colon (0,1)\rightarrow \R$ is nonincreasing and let $D=\{x=(x_1,x_2)\in\R^2: |x|<1\}$. We show that each positive solution of
\Delta u + f(|x|,u) =0 \quad\text{in $D$,} \qquad u=0 \quad\text{on $\partial D$}
which satisfies $u(r,\theta)= u(r,\theta+2\pi/n)$ by the polar coordinates is radially symmetric and $u_r(|x|)<0$ for each $r=|x| \in (0,1)$. We apply our result to the H\'enon equation.

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