A property of representable functions?
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Recall that a function $f:mathbb{N}^krightarrowmathbb{N}$ is representable in Peano arithmetic if there exists a formula $varphi(x_1,dots ,x_k,y)$ such that for every $n_1,dots,n_k,minmathbb{N}$ , If $m=f(n_1,dots,n_k)$ then $mathcal{A}vdash varphi(underline{n_1},dots ,underline{n_k},underline{m})$ If $mneq f(n_1,dots,n_k)$ then $mathcal{A}vdash negvarphi(underline{n_1},dots ,underline{n_k},underline{m})$ Here, $mathcal{A}$ is the theory (set of axioms) of Peano arithmetic, and $underline{n}$ is the term $S(S(dots S(0)dots))$ (with $n$ operations of $S$ ). I have two related questions regarding this definition. Suppose that $f$ is representable by a formula $varphi(x_1,dots ,x_k,y)$ (as defined above); Is it necessarily true that for every $n_1,dots,n_k$ , $$mathcal{A}vdashe...