On an intrinsic characterization of self-adjoint $C^\ast $-Segal algebras

Author(s):  
Subhash J. Bhatt ◽  
Prakash A. Dabhi
2020 ◽  
Vol 8 (1) ◽  
pp. 114-165
Author(s):  
Tetsu Toyoda

AbstractGromov (2001) and Sturm (2003) proved that any four points in a CAT(0) space satisfy a certain family of inequalities. We call those inequalities the ⊠-inequalities, following the notation used by Gromov. In this paper, we prove that a metric space X containing at most five points admits an isometric embedding into a CAT(0) space if and only if any four points in X satisfy the ⊠-inequalities. To prove this, we introduce a new family of necessary conditions for a metric space to admit an isometric embedding into a CAT(0) space by modifying and generalizing Gromov’s cycle conditions. Furthermore, we prove that if a metric space satisfies all those necessary conditions, then it admits an isometric embedding into a CAT(0) space. This work presents a new approach to characterizing those metric spaces that admit an isometric embedding into a CAT(0) space.


2004 ◽  
Vol 11 (4) ◽  
pp. 613-633
Author(s):  
V. Baladze ◽  
L. Turmanidze

Abstract Border homology and cohomology groups of pairs of uniform spaces are defined and studied. These groups give an intrinsic characterization of Čech type homology and cohomology groups of the remainder of a uniform space.


2007 ◽  
Vol 15 (1-2) ◽  
pp. 109-118 ◽  
Author(s):  
Richard N. Ball ◽  
Anthony W. Hager ◽  
Joanne Walters-Wayland

1992 ◽  
Vol 33 (2) ◽  
pp. 670-681 ◽  
Author(s):  
Carles Bona ◽  
Bartolomé Coll ◽  
Juan Antonio Morales

2006 ◽  
Vol 92 (3) ◽  
pp. 423-427 ◽  
Author(s):  
Alejandro Jofré ◽  
Jorge Rivera Cayupi

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