Examples are presented of Σ₁¹-universal preorders arising by requiring the existence of particular surjective functions. These are: the relation of epimorphism between countable graphs; the relation of being a continuous image (or a continuous image of some specific kind) for continua; the relation of being continuous open image for dendrites.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-fm187-3-1,
author = {Riccardo Camerlo},
title = {Universal analytic preorders arising from surjective functions},
journal = {Fundamenta Mathematicae},
volume = {185},
year = {2005},
pages = {193-212},
zbl = {1096.03059},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-fm187-3-1}
}
Riccardo Camerlo. Universal analytic preorders arising from surjective functions. Fundamenta Mathematicae, Tome 185 (2005) pp. 193-212. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-fm187-3-1/