Abstract
In this paper, we give new constructions of Urysohn universal ultrametric spaces. We first characterize a Urysohn universal ultrametric subspace of the space of all continuous functions whose images contain the zero, from a zero-dimensional compact Hausdorff space without isolated points into the space of non-negative real numbers equipped with the nearly discrete topology. As a consequence, the whole function space is Urysohn universal, which can be considered as a non-Archimedean analog of Banach-Mazur theorem. As a more application, we prove that the space of all continuous pseudo-ultrametrics on a zero-dimensional compact Hausdorff space with an accumulation point is a Urysohn universal ultrametric space. This result can be considered as a variant of Wan’s construction of Urysohn universal ultrametric space via the Gromov-Hausdorff ultrametric space.
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Acknowledgments
The author would like to thank Tatsuya Goto for helpful comments. The author would also like to thank the referee for helpful suggestions and valuable comments.
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This work was supported by ongoing institutional funding. No additional grants to carry out or direct this particular research were obtained.
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Ishiki, Y. Constructions of Urysohn Universal Ultrametric Spaces. P-Adic Num Ultrametr Anal Appl 15, 266–283 (2023). https://doi.org/10.1134/S2070046623040027
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DOI: https://doi.org/10.1134/S2070046623040027