5 papers
Medvedev logic is undecidable
Rodrigo Nicolau Almeida, Søren Brinck Knudstorp
We show that Medvedev's logic of finite problems, a well-known superintuitionistic logic, is undecidable. The key method is a reduction from the periodic tiling problem to non-theo…
Coequivalence Relations and Descent in Modal Logic
Rodrigo Nicolau Almeida, Matteo De Berardinis
A coequivalence relation over a modal logic L is a formula in two tuples of propositional variables of the same length such that the logic L proves it to be an equivalence relation…
Uniform Local Tabularity in Intuitionistic Logic
Rodrigo Nicolau Almeida
By contrast with S4, the analysis of local tabularity above IPC has provided a difficult challenge. This paper studies a strengthening of local tabularity - uniform local tabularit…
Unification with Simple Variable Restrictions and Admissibility of -rules
Rodrigo Nicolau Almeida, Silvio Ghilardi
We develop a method to recognize admissibility of -rules, relating this problem to a specific instance of the unification problem with linear constants restriction, called h…
Colimits of Heyting Algebras through Esakia Duality
Rodrigo Nicolau Almeida
In this note we generalize the construction, due to Ghilardi, of the free Heyting algebra generated by a finite distributive lattice, to the case of arbitrary distributive lattices…