Star operations on overrings of Prufer domains

摘要

Let R be a Prufer domain. We begin with two questions: (Q1) If R has only finitely many star operations, is the same true for each overring of R? and (Q2) If each proper overring of R has only finitely many star operations, is the same true for R? We show that both questions have negative answers in general, we give a complete description of when (Q1) has a positive answer (loosely, R must be almost strongly discrete), and we show that for a finite dimensional Prufer domain, the answer to (Q2) is always yes. We then study star regular Prufer domains, that is, Prufer domains R such that Star(T)Star(R) for each overring T of R, and we compute the number of star operations on some particular Prufer domains.