"new foundations must give new math"

from "The Basic Picture. Structures for constructive topology"

by Giovanni Sambin, Oxford University Press, forthcoming

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Under the patronage of

Dipartimento di Matematica Pura ed Applicata, Università degli Studi di Padova, Italy

University of Padova, Italy

AILA (Italian Association of Logic and Applications), whose first president was Giovanni Sambin (from 1987 to 1994).

Abstracts » Negri

Sara Negri
Helsinki

SA systematic approach to completeness and decidability for modal logic

A modular way of generating sequent calculi for a wide class of modal and non-classical logics is presented.

The calculi contain labels and explicit accessibility relations as part of their syntax and have all the structural rules admissible.

Completeness with respect to Kripke semantics is proved in a uniform and direct way by a Sch\"utte-style argument: for every sequent, either a proof is found or a countermodel is generated. This is contrasted with Henkin-style completeness proofs for modal logic.

It is shown through the case of provability logic how the completeness proof can give at the same time a decision procedure.