Email Gateway (Aug 22 2022 at 16:20): Email Gateway (Aug 22 2022 at 16:20):From: Gerwin.Klein@data61.csiro.au
And another new entry in the AFP:
The Kuratowski Closure-Complement Theorem
by Peter Gammie and Gianpaolo Gioiosa
We discuss a topological curiosity discovered by Kuratowski (1922): the fact that the number of distinct operators on a topological space generated by compositions of closure and complement never exceeds 14, and is exactly 14 in the case of R. In addition, we prove a theorem due to Chagrov (1982) that classifies topological spaces according to the number of such operators they support.
https://www.isa-afp.org/entries/Kuratowski_Closure_Complement.html
Enjoy!
Gerwin
Last updated: Nov 21 2024 at 12:39 UTC