String Isomorphism

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An important problem in computational complexity.

String

\(S\): a set.

\(A\): an alphabet. Yet another set.

\(\sigma : S \rightarrow A\): a string. Map from \(S\) to \(A\).

\(p:S \leftrightarrow S\): a bijection from \(S\) to \(S\).

\({Sym}_S = \{ p \}\): group of all permutations of \(S\). Symmetric group.

\(G\): subgroup of \({Sym}_S\).

String Isomorphism

\(\sigma_1\): string.

\(\sigma_2\): string.

\(G\): subgroup of \({Sym}_S\).

Question

Is there some \(p \in G\) such that \(p(\sigma_1) = \sigma_2\) ?