Pantachy

Not to be confused with pantarchy or pentarchy.

In mathematics, a pantachy or pantachie (from the Greek word πανταχη meaning everywhere) is a maximal totally ordered subset of a partially ordered set, especially a set of equivalence classes of sequences of real numbers. The term was introduced by du Bois-Reymond (1879, 1882) to mean a dense subset of an ordered set, and he also introduced "infinitary pantachies" to mean the ordered set of equivalence classes of real functions ordered by domination, but as Felix Hausdorff pointed out this is not a totally ordered set. Hausdorff (1907) redefined a pantachy to be a maximal totally ordered subset of this set.

References

du Bois-Reymond, Paul (1879), "Erläuterungen zu den Anfangsgründen der Variationsrechnung", Mathematische Annalen 15 (2): 283–314, doi:10.1007/BF01444144
du Bois-Reymond, P. (1882), Die allgemeine Funktionentheorie, Tübingen
Hausdorff (1907), "Untersuchungen über Ordnungstypen IV,V", Ber. über die Verhandlungen der Königl. Sächs. Ges. der Wiss. zu Leipzig. Math.-phys. Klasse 59: 84–159 English translation in Hausdorff (2005)
Hausdorff, F. (1914), Grundzüge der Mengenlehre, Leipzig: Veit & Co
Hausdorff, Felix (2005), Plotkin, J. M., ed., Hausdorff on ordered sets, History of Mathematics 25, Providence, RI: American Mathematical Society, ISBN 0-8218-3788-5, MR 2187098

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