What is an R-trivial language? What is an R-trivial monoid?
Context: Formal languages. Afaik, R-trivial languages is a subset of the starfree languages.
I mostly have background in formal languages and automata theory but not so much with the syntactic monoid characterization. So it would be nice to give a basic definition with maybe a small example of such a language.
(In order to support multiple QA-sites because I don't want to have any QA-site stay behind and to have that question also represented there, I have also posted this question on these other sites: stackoverflow.com, cstheory.stackexchange.com, mathoverflow.net. In general I am against cross-posting but in this case, as they all have the same goal to be a complete reference of questions in the specific area, having the question cross posted is the best thing you can do.)