Asymptotic centers in 𝑐₀, 𝑐 and π‘š

Author(s):  
Teck-Cheong Lim
Keyword(s):  
1980 β—½  
Vol 32 (2) β—½  
pp. 421-430 β—½  
Author(s):  
Teck-Cheong Lim

Let X be a Banach space and B a bounded subset of X. For each x ∈ X, define R(x) = sup{β€–x – yβ€– : y ∈ B}. If C is a nonempty subset of X, we call the number R = inΖ’{R(x) : x ∈ C} the Chebyshev radius of B in C and the set the Chebyshev center of B in C. It is well known that if C is weakly compact and convex, then and if, in addition, X is uniformly convex, then the Chebyshev center is unique; see e.g., [9].Let {BΞ± : Ξ± ∈ ∧} be a decreasing net of bounded subsets of X. For each x ∈ X and each Ξ± ∈ ∧, define


2010 β—½  
Vol 2010 β—½  
pp. 1-5
Author(s):  
A. Kaewkhao β—½  
K. Sokhuma

We introduce a class of nonlinear continuous mappings defined on a bounded closed convex subset of a Banach spaceX. We characterize the Banach spaces in which every asymptotic center of each bounded sequence in any weakly compact convex subset is compact as those spaces having the weak fixed point property for this type of mappings.


1989 β—½  
Vol 57 (1) β—½  
pp. 40-47 β—½  
Author(s):  
Norimichi Hirano β—½  
Kazuo Kido β—½  
Wataru Takahashi

2011 β—½  
Vol 2011 β—½  
pp. 1-21 β—½  
Author(s):  
S. Dhompongsa β—½  
N. Nanan

We use an approach on ultra-asymptotic centers to obtain fixed point theorems for two classes of nonself multivalued mappings. The results extend and improve several known ones.


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