Thom-Boardman singularities and monoidal transforms
Let be the ring of integer valued polynomials over . This ring is known to be a Prüfer domain. But it seems there does not exist an algorithm for inverting a nonzero finitely generated ideal of . In this note we show how to obtain such an algorithm by deciphering a classical abstract proof that uses localisations of at all prime ideals of . This confirms a general program of deciphering abstract classical proofs in order to obtain algorithmic proofs.
Let be an integral domain with quotient field and a polynomial of positive degree in . In this paper we develop a method for studying almost principal uppers to zero ideals. More precisely, we prove that uppers to zero divisorial ideals of the form are almost principal in the following two cases: – , the ideal generated by the leading coefficients of , satisfies . – as the -submodule of is of finite type. Furthermore we prove that for we have: – . – If there exists , then ...
Let be a completely regular Hausdorff space and, as usual, let denote the ring of real-valued continuous functions on . The lattice of -ideals of has been shown by Martínez and Zenk (2005) to be a frame. We show that the spectrum of this lattice is (homeomorphic to) precisely when is a -space. This we actually show to be true not only in spaces, but in locales as well. Recall that an ideal of a commutative ring is called a -ideal if whenever two elements have the same annihilator and...