Improved Approximation Algorithms for the Freeze-Tag Problem

In the Freeze-Tag Problem, the objective is to awaken a set of \asleep" robots, starting with only one \awake" robot. A robot awakens a sleeping robot by moving to the sleeping robot's position. When a robot awakens, it is available to assist in awakening other slumbering robots. The objective is to compute an optimal awakening schedule such that all robots are awake by time t , for the smallest possible value of t . Because of its resemblance to the children's game of freeze-tag, this problem has been called Freeze-Tag Problem (FTP)