Algorithmic complexity and efficiency of a ratchet

Molecular motors are characterized by a high degree of efficiency of energy transformation in the presence of thermal fluctuations. A fundamental ques tion is how the efficiency of thermal ratchets depend on temperature and th e flow of physical information (or negentropy). In order to address this qu estion, in this work we have calculated the algorithmic complexity (or Kolm ogorov information entropy) of a smoothly varying potential ratchet, The co mplexity is measured in terms of the average number of bits per time unit n ecessary to specify the sequence generated by the system. For a wide range of values of the flipping rate, the algorithmic complexity is found to be p roportional to the efficiency in a flashing thermal ratchet. In addition, w e find that at low temperatures, the algorithmic complexity (or efficiency) of a thermal ratchet increases with temperature. This is a highly counteri ntuitive result that may be important in the operation of molecular motors. (C) 1999 Elsevier Science B.V, All rights reserved.