We present some results which show the rich and complicated structure of the solutions of
the second order differential equation ẍ+ w (t) g (x)= 0 when the weight w (t) changes sign …

We propose, in the general setting of topological spaces, a definition of two-dimensional
oriented cell and consider maps which possess a property of stretching along the paths with …

By using a topological approach and the relation between rotation numbers and weighted
eigenvalues, we give some multiplicity results for the boundary value problem u′′+ f (t …

PERIODIC POINTS AND CHAOTIC-LIKE DYNAMICS OF PLANAR MAPS ASSOCIATED TO
NONLINEAR HILL’S EQUATIONS WITH INDEFINITE WEIGHT 1. In Page 1 Georgian …

We study fixed point theorems for maps which satisfy a property of stretching a suitably
oriented topological space Z along the paths connecting two disjoint subsets Z− l and Z− r of …

We consider a class of finite-dimensional and infinite-dimensional locally coupled systems
of periodic Hill-type equations with impacts. First, for finite dimensional systems, with …

We prove a fixed point theorem for continuous map**s which satisfy a compression-
expansion condition on the boundary of a N-dimensional cell of ℝN. Our work is motivated …

In this paper we study radial solutions for the following equation Δ u (x)+ f (u (x),| x|)= 0, Δ u
(x)+ f (u (x),| x|)= 0, where x ∈ R^ nx∈ R n, n> 2, f is subcritical for r small and u large and …

We prove structure results for the radial solutions of the semilinear problem Δ⁢ u+ λ⁢(| x|)| x|
2⁢ u+ f⁢(u⁢(x),| x|)= 0, where λ is a function and f is superlinear in the u-variable. As …

We describe the qualitative properties of the solutions of the second order scalar equation
x+ q (t) g (x)= 0, where q is a changing sign function, and consider the problem of existence …