FOM: Thomae and non-archimedian domains
Walter Felscher
walter.felscher at uni-tuebingen.de
Wed Nov 26 09:33:09 EST 1997
Bill Tait, on Nov.12th, wrote in connection with Goedel and
infinitesimals that
Cantor is quoted by Dauben as saying that Johannes Thomae
(who had an office down the hall from Frege) was the
first to ``infect mathematics with the Cholera-Bacillus
of infinitesimals''.
While I do not know what Cantor actually may have referred
to, Thomae (1840-1921 , since 1872 Professor in Halle, since
1879 in Jena) does have a documentable connection, not with
infinitemals, but with non-archimedian extensions of the
reals: in his
Abrisz einer Theorie der complexen Funktionen, Halle 1870
and his
Elementare Theorie der analytischen Functionen einer
complexen Vernderlichen., 2te Aufl., Halle 1898
he represented the orders of growth of real functions by
lexicographically ordered semigroups of sequences of
integers. It then was Paul du Bois-Reymond 1882 who
expressed the idea that the totality of orders of growth
(which he called the infinitaere Pantachie) should be viewed
as an expansion of the continuum; for a more modern
presentation of his work cf. G.H.Hardy, Orders of Infinity,
Cambridge 1924.
It may not be superfluous to point out that this achievement
of Thomae's is NOT connected with his opinions on the
foundation of numbers, analyzed so masterfully in Frege's
"Ueber die Zahlen des Herr Thomae".
W.F.
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