Fixed points of asymptotically regular mappings in spaces with uniformly normal structure

Jarosław Górnicki

Displaying similar documents to “Fixed points of asymptotically regular mappings in spaces with uniformly normal structure”

Fixed points of periodic and firmly lipschitzian mappings in Banach spaces

Krzysztof Pupka (2012)

Commentationes Mathematicae Universitatis Carolinae

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W.A. Kirk in 1971 showed that if $T : C \to C$ , where $C$ is a closed and convex subset of a Banach space, is $n$ -periodic and uniformly $k$ -lipschitzian mapping with $k < k_{0} (n)$ , then $T$ has a fixed point. This result implies estimates of $k_{0} (n)$ for natural $n \geq 2$ for the general class of $k$ -lipschitzian mappings. In these cases, $k_{0} (n)$ are less than or equal to 2. Using very simple method we extend this and later results for a certain subclass of the family of $k$ -lipschitzian mappings. In the paper we show that $k_{0} (3) > 2$ in any Banach...

Separated sequences in uniformly convex Banach spaces

J. M. A. M. van Neerven (2005)

Colloquium Mathematicae

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We give a characterization of uniformly convex Banach spaces in terms of a uniform version of the Kadec-Klee property. As an application we prove that if (xₙ) is a bounded sequence in a uniformly convex Banach space X which is ε-separated for some 0 < ε ≤ 2, then for all norm one vectors x ∈ X there exists a subsequence $(x_{n_{j}})$ of (xₙ) such that $i n f_{j \neq k} | | x - (x_{n_{j}} - x_{n_{k}}) | | \geq 1 + δ_{X} (2 / 3 ε)$ , where $δ_{X}$ is the modulus of convexity of X. From this we deduce that the unit sphere of every infinite-dimensional uniformly convex Banach space...

Separated sequences in asymptotically uniformly convex Banach spaces

Sylvain Delpech (2010)

Colloquium Mathematicae

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We prove that the unit sphere of every infinite-dimensional Banach space X contains an α-separated sequence, for every $0 < α < 1 + δ ̅_{X} (1)$ , where $δ ̅_{X}$ denotes the modulus of asymptotic uniform convexity of X.

The generalized Day norm. Part II. Applications

Monika Budzyńska, Aleksandra Grzesik, Mariola Kot (2017)

Annales Universitatis Mariae Curie-Sklodowska, sectio A – Mathematica

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In this paper we prove that for each $1 < p, \tilde{p} < \infty$ , the Banach space $(l^{\tilde{p}}, {∥\cdot∥}_{\tilde{p}})$ can be equivalently renormed in such a way that the Banach space $(l^{\tilde{p}}, {∥\cdot∥}_{L, α, β, p, \tilde{p}})$ is LUR and has a diametrically complete set with empty interior. This result extends the Maluta theorem about existence of such a set in $l^{2}$ with the Day norm. We also show that the Banach space $(l^{\tilde{p}}, {∥\cdot∥}_{L, α, β, p, \tilde{p}})$ has the weak fixed point property for nonexpansive mappings.

Multivalued pseudo-contractive mappings defined on unbounded sets in Banach spaces

Claudio H. Morales (1992)

Commentationes Mathematicae Universitatis Carolinae

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Let $X$ be a real Banach space. A multivalued operator $T$ from $K$ into $2^{X}$ is said to be pseudo-contractive if for every $x, y$ in $K$ , $u \in T (x)$ , $v \in T (y)$ and all $r > 0$ , $∥ x - y ∥ \leq ∥ (1 + r) (x - y) - r (u - v) ∥$ . Denote by $G (z, w)$ the set ${u \in K : ∥ u - w ∥ \leq ∥ u - z ∥}$ . Suppose every bounded closed and convex subset of $X$ has the fixed point property with respect to nonexpansive selfmappings. Now if $T$ is a Lipschitzian and pseudo-contractive mapping from $K$ into the family of closed and bounded subsets of $K$ so that the set $G (z, w)$ is bounded for some $z \in K$ and some $w \in T (z)$ , then $T$ has a fixed point in $K$ . ...

Reflexivity and approximate fixed points

Eva Matoušková, Simeon Reich (2003)

Studia Mathematica

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A Banach space X is reflexive if and only if every bounded sequence xₙ in X contains a norm attaining subsequence. This means that it contains a subsequence $x_{n_{k}}$ for which $s u p_{f \in S_{X *}} l i m s u p_{k \to \infty} f (x_{n_{k}})$ is attained at some f in the dual unit sphere $S_{X *}$ . A Banach space X is not reflexive if and only if it contains a normalized sequence xₙ with the property that for every $f \in S_{X *}$ , there exists $g \in S_{X *}$ such that $l i m s u p_{n \to \infty} f (x ₙ) < l i m i n f_{n \to \infty} g (x ₙ)$ . Combining this with a result of Shafrir, we conclude that every infinite-dimensional Banach space contains an unbounded...

The Brouwer Fixed Point Theorem for Some Set Mappings

Dariusz Miklaszewski (2013)

Bulletin of the Polish Academy of Sciences. Mathematics

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For some classes $X \subset 2^{ₙ}$ of closed subsets of the disc ₙ ⊂ ℝⁿ we prove that every Hausdorff-continuous mapping f: X → X has a fixed point A ∈ X in the sense that the intersection A ∩ f(A) is nonempty.

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Wadie Aziz, José A. Guerrero, L. Antonio Azócar, Nelson Merentes (2016)

Discussiones Mathematicae, Differential Inclusions, Control and Optimization

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In this paper we study existence and uniqueness of solutions for the Hammerstein equation $u (x) = v (x) + λ \int_{I_{a}^{b}} K (x, y) f (y, u (y)) d y$ in the space of function of bounded total $ϕ$ -variation in the sense of Hardy-Vitali-Tonelli, where $λ \in ℝ$ , $K : I_{a}^{b} \times I_{a}^{b} ⟶ ℝ$ and $f : I_{a}^{b} \times ℝ ⟶ ℝ$ are suitable functions. The existence and uniqueness of solutions are proved by means of the Leray-Schauder nonlinear alternative and the Banach contraction mapping principle.

On $C_{0 \cdot}$ multi-contractions having a regular dilation

Dan Popovici (2005)

Studia Mathematica

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Commuting multi-contractions of class $C_{0 \cdot}$ and having a regular isometric dilation are studied. We prove that a polydisc contraction of class $C_{0 \cdot}$ is the restriction of a backwards multi-shift to an invariant subspace, extending a particular case of a result by R. E. Curto and F.-H. Vasilescu. A new condition on a commuting multi-operator, which is equivalent to the existence of a regular isometric dilation and improves a recent result of A. Olofsson, is obtained as a consequence. ...