Let be a measurable space, a Banach space whose characteristic of noncompact convexity is less than 1, a bounded closed convex subset of , the family of all compact convex subsets of We prove that a set-valued nonexpansive mapping has a fixed point. Furthermore, if is separable then we also prove that a set-valued nonexpansive operator has a random fixed point.
We study a coincidence problem of the form A(x) ∈ ϕ (x), where A is a linear Fredholm operator with nonnegative index between Banach spaces and ϕ is a multivalued A-fundamentally contractible map (in particular, it is not necessarily compact). The main tool is a coincidence index, which becomes the well known Leray-Schauder fixed point index when A=id and ϕ is a compact singlevalued map. An application to boundary value problems for differential equations in Banach spaces is given.
In this note we derive a theorem about the common fixed point set of commuting nonexpansive mappings defined in Cartesian products of separable spaces. The proof is based on a method due to R. E. Bruck.
In this paper, we first establish the dual form of Knaster- Kuratowski-Mazurkiewicz principle which is a hyperconvex version of corresponding result due to Shih. Then Ky Fan type matching theorems for finitely closed and open covers are given. As applications, we establish some intersection theorems which are hyperconvex versions of corresponding results due to Alexandroff and Pasynkoff, Fan, Klee, Horvath and Lassonde. Then Ky Fan type best approximation theorem and Schauder-Tychonoff fixed point...
The existence of bounded solutions for equations x' = A(t)x + r(x,t) is proved, where the linear part is exponentially dichotomic and the nonlinear term r satisfies some weak conditions.
We introduce the relative fixed point index for a class of noncompact operators on special subsets of non locally convex spaces.
We consider a Banach space, which comes naturally from and it appears in the literature, and we prove that this space has the fixed point property for non-expansive mappings defined on weakly compact, convex sets.
We show that every subspace of finite codimension of the space C[0,1] is extremal with respect to the minimal displacement problem.
We give a lower bound for the minimal displacement characteristic in the space l ∞.