On the deterministic code capacity region of an arbitrarily varying multiple-access channel under list decoding

We study the capacity region C
_L
of an arbitrarily varying multiple-access channel (AVMAC) for deterministic codes with decoding into a list of a fixed size L and for the average error probability criterion. Motivated by known results in the study of fixed size list decoding for a point-to-point arbitrarily varying channel, we define for every AVMAC whose capacity region for random codes is nonempty, a nonnegative integer U called its symmetrizability. It is shown that for every L ≤ U, C
_L
has an empty interior, and for every L ≥ (U +1)
²
, C
_L
equals the capacity region of the AVMAC for random codes with a known single-letter characterization.