Shrinkage of de Morgan formulae under restriction

Abstract

It is shown that a random restriction leaving only a fraction in of the input variables unassigned reduces the expected de Morgan formula size of the induced function by a factor of O( in /sup 1.63/). This is an improvement over previous results. The new exponent yields an increased lower bound of approximately n/sup 2.63/ for the de Morgan formula size of a function in P defined by A.E. Andreev (1987). This is the largest lower bound known, even for functions in NP.<>