Abstract
The notion of ultrametrics can be considered as a zero-dimensional analogue of ordinary metrics, and it is expected to prove ultrametric versions of theorems on metric spaces. In this paper, we provide ultrametric versions of the Arens-Eells isometric embedding theorem of metric spaces, the Hausdorff extension theorem of metrics, the Niemytzki-Tychonoff characterization theorem of the compactness, and the author’s interpolation theorem of metrics and theorems on dense subsets of spaces of metrics.
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References
R. F. Arens and J. Eells, Jr, “On embedding uniform and topological spaces,” Pacific. J. Math. 6, 397–403 (1956).
S. A. Bogatyi, “Metrically homogeneous spaces,” Russian Math. Surveys 57 (2), 221–240 (2002).
N. Brodskiy, J. Dydak, J. Higes and A. Mitra, “Dimension zero at all scales,” Topology Appl. 154, 2729–2740 (2007).
D. Burago, Y. Burago and S. Ivanov, A Course in Metric Geometry, Graduate Studies in Mathematics 33 (Amer. Math. Soc., Providence, RI, 2001).
L. W. Cohen and C. Goffman, “On the metrization of uniform space,” Proc. Amer. Math. Soc. 1 (6), 750–753 (1950).
G. Conant, “Distance structures for generalized metric spaces,” Ann. Pure Appl. Logic 168 (3), 622–650 (2017).
A. B. Comicheo and K. Shamseddine, “Summary on non-Archimedean valued field,” in Advances in Ultrametric Analysis, Contemporary Mathematics 704, 1–36 (Amer. Math. Soc., Providence, RI, 2018).
A. B. Comicheo, “Generalized open mapping theorem for \(X\)-normed spaces,” \(p\)-Adic Numbers Ultrametric Anal. Appl. 11 (2), 135–150 (2019).
P. Corazza, “Introduction to metric-preserving functions,” Amer. Math. Monthly 106 (4), 309–323 (1999).
J. Dancis, “Each closed subset of metric space \(X\) with \(\mathrm{Ind}\ X=0\) is a retract,” Houston J. Math. 19 (4), 541–550 (1993).
C. Delhommé, C. Laflamme, M. Pouzet and N. Sauer, “Indivisible ultrametric space,” Topology Appl. 155 (14), 1462–1478 (2008).
D. Dordovskyi, O. Dovgoshey and E. Petrov, “Diameter and diametrical pairs of points in ultrametric spaces,” \(p\)-Adic Numbers Ultrametric Anal. Appl. 3 (4), 253–262 (2011).
O. Dovgoshey, “On ultrametric-preserving functions,” Math. Slovaca 70, 173–182 (2020).
O. Dovgoshey, O. Martio and M. Vuorinen, “Metrization of weighted graphs,” Ann. Comb. 17, 455–476 (2013).
A. A. Dovgoshey and E. A. Petrov, “Subdominant pseudoultrametric on graphs,” Sb. Math. 204, 1131–1151 (2013).
O. Dovgoshey and V. Shcherbak, “The range of ultrametrics, compactness, and separability,” arXiv:2102.10901v2, (2102).
R. Ellis, “Extending continuous functions on zero-dimensional spaces,” Math. Ann. 186, 114–122 (1970).
R. Engelking, General Topology (PWN, Warsawa, 1977).
K. Funano, “Embedding proper ultrametric spaces into \(\ell^p\) and its application to nonlinear Dvoretzky’s theorem,” arXiv:1203.1761, (2012).
S. Gao and C. Shao, “Polish ultrametric Urysohn space and their isometry groups,” Topology Appl. 158 (3), 492–508 (2011).
J. de Groot, “Non-Archimedean metrics in topology,” Proc. Amer. Math. Soc. 7, 948–953 (1956).
J. de Groot, “Some special metrics in general topology,” Colloq. Math. 6, 283–286 (1958).
M. Gromov, with appendices by M. Katz, P. Pansu and S. Semmes, Metric Structures for Riemannian and Non-Riemannian Spaces, Progress in Math. 152 (Birkhauser, 1999).
F. Hausdorff, “Erweiterung einer Homöorphie,” Fund. Math. 16, 353–360 (1930).
F. Hausdorff, “Erweiterung einer stetigen Abbildung,” Fund. Math. 30, 40–47 (1938).
J. Heinonen, Lectures on Analysis on Metric Spaces (Springer-Verlag, New York, 2001).
Y. Ishiki, “Quasi-symmetric invariant properties of Cantor metric spaces,” Ann. Inst. Fourier (Grenoble) 69 (6), 2681–2721 (2019).
Y. Ishiki, “On the Assouad dimension and convergence of metric spaces,” arXiv:1911.07455, (2019).
Y. Ishiki, “An interpolation of metrics and spaces of metrics,” arXiv:2003.13277, (2020).
C. Kuratowski, “Remarques sur les transformations continues des espaces métriques,” Fund. Math. 30, 48–49 (1938).
A. J. Lemin and V. A. Lemin, “On a universal ultrametric space,” Topology Appl. 103, 339–345 (2000).
A. J. Lemin, “Isometric embedding ultrametric (non-Archimedean) spaces in Hilbert space and Lebesgue space,” in \(p\)-Adic Functional Analysis, Lect. Notes Pure Appl. Math. 222, 203–218 (Dekker, New York, 2001).
J. M. Mackay and J. T. Tyson, Conformal Dimension Theory: Theory and Application, Univ. Lecture Ser. 54 (Amer. Math. Soc., 2010).
M. Megrelishvili and M. Shlossberg, “Free non-Archimedean topological groups,” Comment. Math. Univ. Carol. 54 (2), 273–312 (2013).
E. Michael, “Continuous selections. I,” Ann. Math. (2) 63 (2), 361–382 (1956).
E. Michael, “Continuous selections. II,” Ann. Math. (2) 64 (3), 562–580 (1956).
E. Michael, “Selected selection theorems,” Amer. Math. Monthly 63 (4), 233–238 (1956).
V. Niemytzki and A. Tychonoff, “Beweis des Satzes, dass ein metrisierbarer Raum dann und nur dann kompakt ist, wenn er in jeder Metrik vollständig ist,” Fund. Math. 12, 118–120 (1928).
H. Ochsenius and W. H. Schikhof, “Banach spaces over fields with an infinite rank valuation,” in \(p\)-Adic Functional Analysis, Lecture Notes in Pure and Appl. Math. 207, 233–293 (Marcel Dekker, 1999).
D. Qiu, “Geometry of Non-Archimedean Gromov-Hausdorff distance,” \(p\)-Adic Numbers Ultrametric Anal. Appl. 1, 317–337 (2009).
A. M. Robert, A Course in \(p\)-adic Analysis, Graduate Text in Math. 198 (Springer-Verlag, 2000).
A. R. Pears, Dimension Theory of General Spaces (Cambridge Univ. Press, 1975).
P. Pongsriiam and I. Termwuttipong, “Remarks on ultrametrics and metric-preserving functions,” Abstr. Appl. Anal. 2014, 1–9 (2014).
W. H. Schikhof, “Isometrical embeddings of ultrametric spaces into non-Archimedean valued fields,” Indag. Math. 46, 51–53 (1984).
R. Sikorski, “Remarks on some topological spaces of high power,” Fund. Math. 33, 125–136 (1950).
I. S. Stares and J. E. Vaughan, “The Dugundji extension property can fail in \(\omega_{\mu}\)-metrizable spaces,” Fund. Math. 150, 11–16 (1996).
I. Z. Stasyuk, “On a homogeneous operator extending partial ultrametrics,” Matematychni Studii 22 (1), 73–78 (2004).
I. Z. Stasyuk and E. D. Tymchatyn, “Extending pairs of metrics,” Matematychni Studii 35 (2), 215–224 (2011).
A. H. Stone, “Paracompactness and product spaces,” Bull. Amer. Math. Soc. 54 (10), 977–982 (1948).
A. F. Timan and I. A. Vestfrid, “A universality property of Hilbert spaces,” Soviet Math. Dokl. 20, 485–486 (1979).
A. F. Timan and I. A. Vestfrid, “Any separable ultrametric space is isometrically embeddable in \(\ell^2\),” Funct. Anal. Appl. 17, 70–71 (1983).
H. Toruńczyk, “A simple proof of Hausdorff’s theorem on extending metrics,” Fund. Math. 77, 191–193 (1972).
E. D. Tymchatyn and M. M. Zarichnyi, “A note on operators extending partial ultrametrics,” Comment. Math. Univ. Carol. 46 (3), 515–524 (2005).
J. E. Vaughan, “Universal ultrametric spaces of smallest weight,” Topology Proc. 24, 611–619 (1999).
I. A. Vestfrid, “On the universal spaces,” Ukrainian Math. J. 46 (12), 1890–1898 (1994).
Z. Wan, “A novel construction of Urysohn universal ultrametric space via the Gromov-Hausdorff ultrametric,” arXiv:2007.08105, (2020).
S. Warner, Topological Fields, North Holland, Mathematics Studies 157 (North-Holland-Amsterdam, London, New York, Tokyo, 1993).
S. Willard, General Topology (Dover Publications, 2004).
I. Zarichnyi, “Gromov-Hausdorff ultrametric,” arXiv:math/0511436v1, (2005).
Acknowledgments
The author would like to thank Professor Koichi Nagano for his advice and constant encouragement. The author would also like to thank the referee for helpful comments and suggestions.
Funding
The author was supported by JSPS KAKENHI Grant Number 18J21300.
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Ishiki, Y. An Embedding, An Extension, and An Interpolation of Ultrametrics\(^*\). P-Adic Num Ultrametr Anal Appl 13, 117–147 (2021). https://doi.org/10.1134/S2070046621020023
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DOI: https://doi.org/10.1134/S2070046621020023