A note on a extension of Kreisel's conjecture
V. P. Orevkov
Abstract:
Given a theory
$\mathfrak{R}$, let
$\mathfrak{R}\vdash_lA$ means that
$A$ is provable in
$\mathfrak{R}$ in
$l$ steps. Let
$L^*$ be the first order language with a constant
symbol
$O$, a unary function symbol
$'$, a binary predicate
symbol
$=$, ternary predicate symbols
$P$ and
$Q$. The theory in
$L^*$ with the axioms
$\mathbb{R}^*.1$–
$\mathbb{R}^*.13$ defined in §1 of this paper
is denoted by
$\mathbb{R}^*$. The Robinson arithmetic is obtained from
$\mathbb{R}^*$
by replacing the predicate symbols
$P$ and
$Q$ by the function symbols
$+$
and
$\cdot$. Define
$t^{(n)}$ as
$n$-times iteration of
$'$ starting
with
$t$.
THEOREM. There is a natural number
$c_1$ such that for any consistent
extension
$\mathfrak{A}$ of
$\mathbb{R}^*$ there are a formula
$A(a)$ and natural
number
$c_2$ with the following properties: 1)
$\mathfrak{A}\not\vdash\forall x\,A(x)$,
2) for any natural number
$n$
$$
\mathbb{R}^*\vdash_{c_1[\log_2(n+1)+c_2]}A(O^{(n)}).
$$
UDC:
510.66