Page 1 Next

Displaying 1 – 20 of 124

Showing per page

The Banach contraction mapping principle and cohomology

Ludvík Janoš (2000)

Commentationes Mathematicae Universitatis Carolinae

By a dynamical system ( X , T ) we mean the action of the semigroup ( + , + ) on a metrizable topological space X induced by a continuous selfmap T : X X . Let M ( X ) denote the set of all compatible metrics on the space X . Our main objective is to show that a selfmap T of a compact space X is a Banach contraction relative to some d 1 M ( X ) if and only if there exists some d 2 M ( X ) which, regarded as a 1 -cocycle of the system ( X , T ) × ( X , T ) , is a coboundary.

The characteristic of noncompact convexity and random fixed point theorem for set-valued operators

Poom Kumam, Somyot Plubtieng (2007)

Czechoslovak Mathematical Journal

Let ( Ω , Σ ) be a measurable space, X a Banach space whose characteristic of noncompact convexity is less than 1, C a bounded closed convex subset of X , K C ( C ) the family of all compact convex subsets of C . We prove that a set-valued nonexpansive mapping T C K C ( C ) has a fixed point. Furthermore, if X is separable then we also prove that a set-valued nonexpansive operator T Ω × C K C ( C ) has a random fixed point.

The coincidence index for fundamentally contractible multivalued maps with nonconvex values

Dorota Gabor (2000)

Annales Polonici Mathematici

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.

The continuity of superposition operators on some sequence spaces defined by moduli

Enno Kolk, Annemai Raidjõe (2007)

Czechoslovak Mathematical Journal

Let λ and μ be solid sequence spaces. For a sequence of modulus functions Φ = ( ϕ k ) let λ ( Φ ) = { x = ( x k ) ( ϕ k ( | x k | ) ) λ } . Given another sequence of modulus functions Ψ = ( ψ k ) , we characterize the continuity of the superposition operators P f from λ ( Φ ) into μ ( Ψ ) for some Banach sequence spaces λ and μ under the assumptions that the moduli ϕ k ( k ...

Currently displaying 1 – 20 of 124

Page 1 Next