Some strange behaviors of the power series ring R[[X]]

Abstract

Let R be a commutative ring with identity. Let R[X] and R[[X]] be the polynomial ring and the power series ring respectively over R. Being the completion of R[X] (under the X-adic topology), R[[X]] does not always share the same property with R[X]. In this paper, we present some known strange behaviors of R[[X]] compared to those of R[X].