Cooperation in Repeated Games When the Number of Stages is not Commonly Known
证明，在囚徒困境重复博弈中，若对总轮数T的共同知识假设有极小的偏离（如指数级小的不确定性），就能实现合作；更一般地，任何一次性博弈的可行个体理性结果都能被有限重复博弈的子博弈完美均衡逼近。
It is shown that an exponentially small departure from the common knowledge assumption on the number T of repetitions of the prisoners' dilemma already enables cooperation. More generally, with such a departure, any feasible individually rational outcome of any one-shot game can be approximated by a subgame perfect equilibrium of a finitely repeated version of that game. The sense in which the departure from common knowledge is small is as follows: (I) With probability one, the players know T with precision ±K. (ii) With probability 1 −e, the players know T precisely; moreover, this knowledge is mutual of order eT. (iii) The deviation of T from its finite expectation is exponentially small.