S. Bachmann, G.M. Graf, G.B. Lesovik
Time ordering and counting statistics
(63K, Latex with 1 PS figure)

ABSTRACT.  The basic quantum mechanical relation between fluctuations of transported 
charge and current correlators is discussed. It is found that, as a rule, the correlators are to be time-ordered in an unusual way. Instances where the difference with the conventional ordering matters are illustrated by means of a simple scattering model. We apply the results to resolve a discrepancy concerning the third cumulant of charge transport across a quantum point contact.