Published online by Cambridge University Press: 20 November 2018
Kakutani (2) has proved a very general theorem, giving necessary and sufficient conditions for two infinite product measures to be mutually absolutely continuous. To formulate Kakutani's result, let us first recall that a measurable space is a pair (E, B), where B denotes a Borel field (also called σ-ring) of subsets of E, and a measure m on this space is a countably additive set function on B (see Halmos (1)).
This paper was written in the Soviet Union while the author participated in the exchange program with the Soviet Academy of Sciences. He is indebted to the National Academy of Sciences for financial support.