Embeddability of locally finite metric spaces into Banach spaces is finitely determined

Abstract

The main purpose of the paper is to prove the following results: • Let A be a locally finite metric space whose finite subsets admit uniformly bilipschitz embeddings into a Banach space X. Then A admits a bilipschitz embedding into X. • Let A be a locally finite metric space whose finite subsets admit uniformly coarse embeddings into a Banach space X. Then A admits a coarse embedding into X. These results generalize previously known results of the same type due to Brown–Guentner (2005), Baudier (2007), Baudier–Lancien (2008), and the author (2006, 2009). One of the main steps in the proof is: each locally finite subset of an ultraproduct XU admits a bilipschitz embedding into X. We explain how this result can be used to prove analogues of the main results for other classes of embeddings. 2010 Mathematics Subject Classification: Primary: 46B85; Secondary: 05C12, 46B08, 46B20, 54E35