Explicit modal logic was introduced by S. Artemov. Whereas the traditional modal logic uses atoms ☐
F with a possible semantics “
F is provable”, the explicit modal logic deals with atoms of form
t:F, where
t is a
proof polynomial denoting a specific proof of a formula
F. Artemov found the explicit modal logic
$
\mathcal{L}\mathcal{P}
$
\mathcal{L}\mathcal{P}
in this new format and built an algorithm that recovers explicit proof polynomials corresponding to modalities in every derivation
in K. Gödel’s modal provability calculus
$
\mathcal{S}4
$
\mathcal{S}4
. In this paper we study the complexity of
$
\mathcal{L}\mathcal{P}
$
\mathcal{L}\mathcal{P}
as well as the complexity of explicit counterparts of the modal logics
$
\mathcal{K}, \mathcal{D}, \mathcal{T}, \mathcal{K}\mathcal{A}, \mathcal{D}4
$
\mathcal{K}, \mathcal{D}, \mathcal{T}, \mathcal{K}\mathcal{A}, \mathcal{D}4
found by V. Brezhnev. The main result: the satisfiability problem for each of these explicit modal logics belongs to the
class ∑
2
p 2 of the polynomial hierarchy. Similar problem for the original modal logics is known to be PSPACE-complete. Therefore, explicit
modal logics have much better upper complexity bounds than the original modal logics.
The author is partially supported by the grant DAAH04-96-1-0341, by DAPRA under program LPE, project 34145.