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Kolmogorov complexity and the asymptotic bound for error-correcting codes

The set of all error--correcting block codes over a fixed alphabet with $q$ letters determines a recursively enumerable set of rational points in the unit square with coordinates $(R,δ)$:= (relative transmission rate, relative minimal distance). Limit points of this set form a closed subset, defined by $R\le α_q(δ)$, where $α_q(δ)$ is a continuous decreasing function called asymptotic bound. Its existence was proved by the first--named author in 1981 ([Man1]), but no approaches to the computation of this function are known, and in [Man5] it was even suggested that this function might be uncomputable in the sense of constructive analysis. In this note we show that the asymptotic bound becomes computable with the assistance of an oracle producing codes in the order of their growing Kolmogorov complexity. Moreover, a natural partition function involving complexity allows us to interpret the asymptotic bound as a curve dividing two different thermodynamic phases of codes.