We prove that any countable set of surjective functions on an infinite set of cardinality $\aleph_n$ with $n\in\mathbb N$ can be generated by at most $n^2/2+9n/2+7$ surjective functions of the same set; and there exist $n^2/2+9n/2+7$ surjective functions that cannot be generated by any smaller number of surjections.
We also present several analogous results for other classical infinite transformation semigroups such as the injective functions, the Baer–Levi semigroups, and the Schützenberger monoids.
@article{10_4064_fm213_1_4,
author = {J. D. Mitchell and Y. P\'eresse},
title = {Generating countable sets of surjective functions},
journal = {Fundamenta Mathematicae},
pages = {67--93},
year = {2011},
volume = {213},
number = {1},
doi = {10.4064/fm213-1-4},
language = {en},
url = {http://geodesic.mathdoc.fr/articles/10.4064/fm213-1-4/}
}
TY - JOUR
AU - J. D. Mitchell
AU - Y. Péresse
TI - Generating countable sets of surjective functions
JO - Fundamenta Mathematicae
PY - 2011
SP - 67
EP - 93
VL - 213
IS - 1
UR - http://geodesic.mathdoc.fr/articles/10.4064/fm213-1-4/
DO - 10.4064/fm213-1-4
LA - en
ID - 10_4064_fm213_1_4
ER -
%0 Journal Article
%A J. D. Mitchell
%A Y. Péresse
%T Generating countable sets of surjective functions
%J Fundamenta Mathematicae
%D 2011
%P 67-93
%V 213
%N 1
%U http://geodesic.mathdoc.fr/articles/10.4064/fm213-1-4/
%R 10.4064/fm213-1-4
%G en
%F 10_4064_fm213_1_4
J. D. Mitchell; Y. Péresse. Generating countable sets of surjective functions. Fundamenta Mathematicae, Tome 213 (2011) no. 1, pp. 67-93. doi: 10.4064/fm213-1-4