Some Uses of Dilators in Combinatorial Problems. II
Abrusci, V. Michele ; Girard, Jean-Yves ; Wiele, Jacques Van De
J. Symbolic Logic, Tome 55 (1990) no. 1, p. 32-40 / Harvested from Project Euclid
We study increasing $F$-sequences, where $F$ is a dilator: an increasing $F$-sequence is a sequence (indexed by ordinal numbers) of ordinal numbers, starting with 0 and terminating at the first step $x$ where $F(x)$ is reached (at every step $x + 1$ we use the same process as in decreasing $F$-sequences, cf. [2], but with "+ 1" instead of "- 1"). By induction on dilators, we shall prove that every increasing $F$-sequence terminates and moreover we can determine for every dilator $F$ the point where the increasing $F$-sequence terminates. We apply these results to inverse Goodstein sequences, i.e. increasing $(1 + Id)_{(\omega)}$-sequences. We show that the theorem every inverse Goodstein sequence terminates (a combinatorial theorem about ordinal numbers) is not provable in $ID_1$. For a general presentation of the results stated in this paper, see [1]. We use notions and results concerning the category ON (ordinal numbers), dilators and bilators, summarized in [2, pp. 25-31].
Publié le : 1990-03-14
Classification: 
@article{1183743183,
     author = {Abrusci, V. Michele and Girard, Jean-Yves and Wiele, Jacques Van De},
     title = {Some Uses of Dilators in Combinatorial Problems. II},
     journal = {J. Symbolic Logic},
     volume = {55},
     number = {1},
     year = {1990},
     pages = { 32-40},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1183743183}
}
Abrusci, V. Michele; Girard, Jean-Yves; Wiele, Jacques Van De. Some Uses of Dilators in Combinatorial Problems. II. J. Symbolic Logic, Tome 55 (1990) no. 1, pp.  32-40. http://gdmltest.u-ga.fr/item/1183743183/