Modal Companion
メモ
In logic, a modal companion of a superintuitionistic (intermediate) logic L is a normal modal logic that interprets L by a certain canonical translation, described below. Modal companions share various properties of the original intermediate logic, which enables to study intermediate logics using tools developed for modal logic.
Ref
$ \Gamma \vDash_\mathsf{P\Lambda} \varphi \iff \tau(\Gamma) \vDash_\mathsf{M\Lambda} \tau(\varphi)
その事実を$ \sf \tau P\Lambda = M\Lambdaとして表すとする.
Examples