Let C(A) denote the class
group of a Krull domain A. Samuel has established (a) C(A) → C(A[[X1,⋯,Xn]]) is
injective, and (b) C(A) → C(A[[X1,⋯,Xn]]) is bijective in Case A is a regular
U.F.D. This note establishes that C(A) → C(A[[X1,⋯,Xn]]) is bijective in Case
A is a regular noetherian domain, thus adding a complement to (a) while
generalizing (b). A corollary of this is that A[[X1,⋯,Xn]]S is a U.F.D. if
A is a regular Noetherian domain and S is the set of nonzero elements of
A.
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