A class of strongly cooperative systems without compactness
It is shown that the uniform exponential stability and the uniform stability at permanently acting disturbances of a sufficiently smooth but not necessarily steady-state solution of a general variational inequality is a consequence of the uniform exponential stability of a zero solution of another (so called linearized) variational inequality.
The following problem of Markus and Yamabe is answered affirmatively: Let f be a local diffeomorphism of the euclidean plane whose jacobian matrix has negative trace everywhere. If f(0) = 0, is it true that 0 is a global attractor of the ODE dx/dt = f(x)? An old result of Olech states that this is equivalent to the question if such an f is injective. Here the problem is treated in the latter form by means of an investigation of the behaviour of f near infinity.
The asymptotic behaviour of a Sturm-Liouville differential equation with coefficient is investigated, where and is a nondecreasing step function tending to as . Let denote the set of those ’s for which the corresponding differential equation has a solution not tending to 0. It is proved that is an additive group. Four examples are given with , , (i.e. the set of dyadic numbers), and .