Research articles
A test for completeness with respect to implicit reducibility in the chain super-intutionistic logics
I. V. Cucu State University of Moldova, Chişinău, Moldova
Аннотация:
We examine chain logics
$C_2,C_3,\dots$, which are intermediary between classical and intuitionistic logics. They are also the logics of pseudo-Boolean algebras of type
$\langle E_m,\&,\vee,\supset,\neg\rangle$, where
$E_m$ is the chain $0<\tau_ 1<\tau_2<\dots<\tau_{m-2}<1$ (
$m=2,3,\dots$). The formula
$F$ is called to be implicitly expressible in logic
$L$ by the system
$\Sigma$ of formulas if the relation
$$
L\vdash(F\sim q)\sim((G_1\sim H_1)\&\dots\&(C_k\sim H_k))
$$
is true, where
$q$ do not appear in
$F$, and formula
$G_i$ and
$H_i$, for
$i=1,\dots, k$, are explicitly expressible in
$L$ via
$\Sigma$ The formula
$F$ is said to be implicitly reducible in logic
$L$ to formulas of
$\Sigma$ if there exists a finite sequence of formulas
$G_1,G_2,\dots,G_l$ where
$G_l$ coincides with
$F$ and for
$j = 1,\dots,l$ the formula
$G_j$ is implicitly expressible in
$L$ by
$\Sigma\cup\{G_1,\dots,G_{j-1}\}$. The system
$\Sigma$ is called complete relative to implicit reducibility in logic
$L$ if any formula is implicitly reducible in
$L$ to
$\Sigma$.
The paper contains the criterion for recognition of completeness with respect to implicit reducibility in the logic
$C_m$, for any
$m=2,3,\dots$ . The criterion is based on 13 closed pre-complete classes of formulas.
Ключевые слова и фразы:
Chain intermediate logic, pseudo-Boolean algebra, expressibility, implicit reducibility, centralizer.
MSC: 16D80,
16D90,
16D20 Поступила в редакцию: 15.07.2005
Язык публикации: английский