6 papers
Surreal limits
Paolo Lipparini, István Mezö
We note that if a sequence of real numbers converges to some limit, then the sequence of the corresponding strings in the surreal sign expansion representation converges, for…
Hypercontact semilattices
Paolo Lipparini
Contact Boolean algebras are one of the main algebraic tools in region-based theory of space. T. Ivanova provided strong motivations for the study of merely semilattices with a con…
A model theory of topology
Paolo Lipparini
An algebraization of the notion of topology has been proposed more than seventy years ago in a classical paper by McKinsey and Tarski. However, in McKinsey and Tarski's setting the…
Semilattices with a congruence
Paolo Lipparini
A specialization semilattice is a semilattice together with a coarser preorder satisfying a compatibility condition. We show that the category of specialization semilattices is iso…
Ivanova contact join-semilattices are not finitely axiomatizable
Paolo Lipparini
We show that the class of Contact join-semilattices, as introduced by T. Ivanova, is not finitely axiomatizable. On the other hand, a simple finite axiomatization exists for the cl…
A short way to directed Jónsson terms
Paolo Lipparini
We show that a variety with Jónsson terms has directed Jónsson terms , for the same value of the indices, solving a problem raised by K…