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A reverse viewpoint on the upper semicontinuity of multivalued maps

Marcio Colombo Fenille (2013)

Mathematica Bohemica

For a multivalued map ϕ : Y ( X , τ ) between topological spaces, the upper semifinite topology 𝒜 ( τ ) on the power set 𝒜 ( X ) = { A X : A } is such that ϕ is upper semicontinuous if and only if it is continuous when viewed as a singlevalued map ϕ : Y ( 𝒜 ( X ) , 𝒜 ( τ ) ) . In this paper, we seek a result like this from a reverse viewpoint, namely, given a set X and a topology Γ on 𝒜 ( X ) , we consider a natural topology ( Γ ) on X , constructed from Γ satisfying ( Γ ) = τ if Γ = 𝒜 ( τ ) , and we give necessary and sufficient conditions to the upper semicontinuity of a multivalued map ϕ : Y ( X , ( Γ ) ) ...

A variational problem for couples of functions and multifunctions with interaction between leaves

Emilio Acerbi, Gianluca Crippa, Domenico Mucci (2012)

ESAIM: Control, Optimisation and Calculus of Variations

We discuss a variational problem defined on couples of functions that are constrained to take values into the 2-dimensional unit sphere. The energy functional contains, besides standard Dirichlet energies, a non-local interaction term that depends on the distance between the gradients of the two functions. Different gradients are preferred or penalized in this model, in dependence of the sign of the interaction term. In this paper we study the lower semicontinuity and the coercivity of the energy...

Admissible maps, intersection results, coincidence theorems

Mircea Balaj (2001)

Commentationes Mathematicae Universitatis Carolinae

We obtain generalizations of the Fan's matching theorem for an open (or closed) covering related to an admissible map. Each of these is restated as a KKM theorem. Finally, applications concerning coincidence theorems and section results are given.

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