Krasnoselskii‐type fixed point theorems with applications to Hammerstein integral equations in spaces

In this paper, we study fixed point theorems and new variants of some nonlinear altenatives of Krasnoselskii type in Banach spaces by using measures of weak noncompactness. Then we give an application to solve a nonlinear Hammerstein integral equation in L¹ spaces.     

Bifurcation points of Hammerstein equations

We apply global bifurcation theorems to systems of nonlinear integral equations of Hammerstein type involving a scalar parameter. To this end, we give sufficient conditions for the continuous dependence, compactness, Fréchet differentiability, and asymptotic linearity of the corresponding operators, which are more general than in the classical setting. These properties are ensured only after passing to some equivalent operator equation which typically contains fractional powers of the linear part. Finally, we show that the abstract hypotheses on the operators correspond to natural hypotheses on the kernel function and the nonlinearity in the Hammerstein equation under consideration.     

Spetral sets II

Sono studiati l’insiemi spettrali delle elementi di algebra di Banach negli termini della esistenza delle partizioni della unita di algebra. Circolarmente isolati l’insiemi spettrali sono caratterizati et una nuova decomposizione di Mbekhta per operatori lineari limitati e ottenuta. We study spectral sets of elements of a Banach algebra in terms of the existence of idempotent partitions of the unit of the algebra. Circularly isolated spectral sets are characterized, and a new Mbekhta decomposition for bounded linear operators is obtained.     

ON TOPOLOGICAL LINEAR CONTRACTIONS ON NORMED SPACES AND APPLICATION

51.IntroductionandPreliminariesThroughoutthispaper(X,11'if)denotesanormedspaceandN(11'II)denotesthecollectionofallnormsonXwhichareequivalentto11'11.Foreach11'if'6N(II'II)andeachr>0,letX.(ll'II')~{xEX:Ilxll'5r}andX?(ll'if')~{xEX.Ilxll'相似文献   

Finite sums of idempotents and logarithmic residues on connected domains

We show that every finite sum of idempotents in a Banach algebra can be represented as the logarithmic residue of some analytic Banach algebra valued function defined on any, given bounded Cauchy domain. Moreover, using this, we can construct a non-invertible analytic Banach algebra valued function which is defined on any given bounded Cauchy domain and whose logarithmic residue is equal to zero., Consequently, the classical theorem concerning logarithmic residues fails in the general situation for all domains, in particular for connected domains.     

Approximating solutions of Hammerstein type equations in Banach spaces

Abstract

Let X be a real Banach space and X^? be its dual. Let F: X → X^? and K: X^? → X be Lipschitz monotone mappings. In this paper an explicit iterative scheme is constructed for approximating solutions of the Hammerstein type equation, 0 = u + KF u, when they exist. Strong convergence of the scheme is obtained under appropriate conditions. Our results improve and unify many of the results in the literature.     

Noncyclic mappings and best proximity pair results in Hilbert and uniformly convex Banach spaces

A new class of noncyclic mappings, called generalized noncyclic relatively nonexpansive, is introduced and used to study the existence of best proximity pairs in the setting of uniformly convex Banach spaces. We also obtain a weak convergence theorem for noncyclic relatively nonexpansive mappings in the setting of Hilbert spaces.     

Existence of solutions for generalized implicit vector variational-like inequalities

In this paper, we introduce a new class of generalized implicit vector variational-like inequalities in Hausdorff topological vector spaces and Banach spaces which contain implicit vector equilibrium problems, implicit vector variational inequalities and implicit vector complementarity problems as special cases. We derive some new results by using the KKM–Fan theorem, under compact and noncompact assumptions on underlying convex sets.     

Banach lattices with the fatou property and optimal domains of kernel operators

New features of the Banach function space L¹_w(v), that is, the space of all v-scalarly integrable functions (with v any vector measure), are exposed. The Fatou property plays an essential role and leads to a new representation theorem for a large class of abstract Banach lattices. Applications are also given to the optimal domain of kernel operators taking their values in a Banach function space.     

Dinamica relativa di una particella con spin: un teorema di unicità

We prove anunicity theorem for spinning particles in the Papapetrou-Tulczyjew scheme; the theorem modifies the conclusive remarks of a preceding paper [1], i.e. the erroneous incompatibility of such scheme. The unicity is given using an intrinsic frame of reference (parallel to the generalized impulsion) and theresolvent equation of the differential problem, in terms of velocity (vectorial parameter).

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Sunto Si dimostra unteorema di unicità per lo schema di Papapetrou-Tulczyjew relativo ad una particella con spin in Relatività generale; il teorema vale a rettificare un precedente lavoro [1] che avanzava erroneamente, per tale schema, l’ipotesi di incompletezza. Il risultato si consegue operando (intrinsecamente) nelriferimento collineare all’impulso generalizzato, attraverso l’equazione risolvente per la velocità.

     

Teoremi di unicità della magnetoidrodinamica in domini illimitati

Riassunto In questa nota si stabiliscono due teoremi di unicità della soluzione per il problema del moto di un fluido omogenco, incomprimibile, perfetto, elettricamente conduttore attorno ad un ostacolo fisso, anch'esso elettricamente conduttore. Nelprimo teorema viene trascurata la corrente di spostamento, mentre nel secondo si tiene conto anche di quest'ultima. Per la dimostrazione si utilizza il “metodo della funzione peso” usato da G. P. Galdi e S. Rionero in un analogo teorema di unicità per magnetofluidi viscosi.

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Summary The Author establishes two solution uniqueness theorems for the problem of homogeneous, incompressible, perfect, electrically conducting fluid motion around a fixed, electrically conducting solid body. In the first theorem displacemt current is disregarded, in the other one this current is considered. The proof is obtained by using the “weight function method” adopted by G. P. Galdi and S. Rionero in an analogous uniqueness theorem for viscous magnetofluids.

     

Optimal and one-complemented subspaces

Let X be a real Banach space and let V ⊂ X be a closed linear subspace. In [4, Prop. 5] it has been proven that if X is strictly convex, reflexive and smooth and V is an optimal subset of X then V is one-complemented in X. In this note we would like to extend this result to non-smooth Banach spaces. In particular, we show that any existence subspace of c,c _o and l ₁ is one-complemented. Also some results concerning non-smooth Musielak-Orlicz sequence spaces equipped with the Luxemburg norm will be presented. The first author was supported by Polish State Committee for Scientific Research Grant KBN 1 PO3A O10 26. Authors’ addresses: Grzegorz Lewicki, Department of Mathematics, Jagiellonian University, 30-059 Kraków, Reymonta 4, Poland; Giulio Trombetta, Department of Mathematics, University of Calabria, 87036 Arcavacata di Rende, Cosenza, Italy     

Integrable solutions of a mixed type operator equation

In this paper we prove the existence of integrable solutions for a generalized mixed type operator equation, which contains many key integral and functional equations appearing frequently in Mathematical literature. Our main tool is a Krasnosel’skii type fixed point theorem recently proved by Latrach and Taoudi, the first author. An existence theory for a class of nonlinear transport equations is also developed.     

Fixed point theorems for nonexpansive maps in Banach spaces

In this work, we present some new versions of fixed point theorems for nonexpansive maps and 1-set contractions defined on closed, convex, not necessarily bounded subsets of Banach spaces. Our proofs rely on a compactness result for an approximate fixed point set. The Kuratowski measure of noncompactness is used throughout. To illustrate the results obtained, some applications to Banach algebras and Hammerstein integral equations are provided.     

Sull'equazione integrale non lineare di Volterra

Sunto Si dà un nuovo teorema che allarga la classe delle equazioni integrali non lineari di Volterra, dotate di un'unica soluzione.

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Summary A new theorem is given, which extends the class of non-linear Volterra integral equations, whose solution exists and is unique.

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A Giovanni Sansone nel suo 70^mo compleanno     

An improvement of a recent closed graph theorem

We obtain a new closed graph theorem which is a substantial improvement of a recent result.     

A hybrid scheme for finite families of equilibrium, variational inequality and fixed point problems

We introduce an iterative process for finding an element in the common fixed point set of finite family of closed relatively quasi-nonexpansive mappings, common solutions of finite family of equilibrium problems and common solutions of finite family of variational inequality problems for monotone mappings in Banach spaces. Our theorem extends and unifies most of the results that have been proved for this important class of nonlinear operators.     

Nonlocal nonlinear differential equations with a measure of noncompactness in Banach spaces

In this paper we give the existence of integral solutions for nonlinear differential equations with nonlocal initial conditions under the assumptions of the Hausdorff measure of noncompactness in separable and uniformly smooth Banach spaces.     

Solution of nonlinear integral equations of Hammerstein type

Let E be a 2-uniformly real Banach space and F,K:E→E be nonlinear-bounded accretive operators. Assume that the Hammerstein equation u+KFu=0 has a solution. A new explicit iteration sequence is introduced and strong convergence of the sequence to a solution of the Hammerstein equation is proved. The operators F and K are not required to satisfy the so-called range condition. No invertibility assumption is imposed on the operator K and F is not restricted to be an angle-bounded (necessarily linear) operator.     

Proprietà funtoriali della coomologia di Allendoerfer-Eells

Riassunto In questa nota è data una dimostrazione del teorema di Allendoerfer e Eells sulla coomologia a coefficienti interi delle varietà, basata sulla caratterizzazione assiomatica della coomologia di Eilenberg e Steenrod.

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Summary A proof of the theorem of Allendoerfer and Eells on the cohomology with coefficients inZ of smooth manifolds is given, based on the axiomatic approach to cohomology due to Eilenberg and Steenrod.