Smooth digraphs modulo primitive positive constructability
Manuel Bodirsky, Florian Starke, Albert Vucaj · arXiv (Cornell University) · 2019
We consider the poset that arises from ordering finite smooth digraphs via pp-constructability. We give a complete description of this poset and, in particular, we prove that it is a distributive lattice. Moreover, we show that in order to separate two smooth digraphs in our poset it suffices to show that the polymorphism clone of one satisfies a prime cyclic loop condition that is not satisfied by the polymorphism clone of the other.