Joaquim Reizi Higuchi

Explicit Two-Variable Bases and the Single-Equation Problem for iEx-Logic

We study Ex-algebras, which capture the common sequent validities of Heyting algebras and orthomodular algebras with Sasaki implication. Over the fixed fundamental-algebra base in the original signature {meet, join, implication, 0, 1}, we prove a two-local representation theorem...

Joint Modal Validities: Explicit Schemas and Partial Decidability Results

An explicit infinite equational schema is given for the formulas valid both in a specified basic modal orthomodular class and in intuitionistic modal logic IK. The same construction treats Wijesekera's propositional constructive modal logic, denoted WK in current terminology, and...