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How rigid the finite ultrametric spaces can be?

2016; Birkhäuser; Volume: 19; Issue: 2 Linguagem: Inglês

10.1007/s11784-016-0329-5

1661-7746

Oleksiy Dovgoshey, Evgeniy Petrov, Hanns‐Martin Teichert,

Advanced Topology and Set Theory

A metric space X is rigid if the isometry group of X is trivial. The finite ultrametric spaces X with |X| ≥ 2 are not rigid since for every such X there is a self-isometry having exactly |X|−2 fixed points. Using the representing trees we characterize the finite ultrametric spaces X for which every self-isometry has at least |X|−2 fixed points. Some other extremal properties of such spaces and related graph theoretical characterizations are also obtained.