Projectivity of pure ideals
In this paper, we deal with the study of quasi-homeomorphisms, the Goldman prime spectrum and the Jacobson prime spectrum of a commutative ring. We prove that, if is a quasi-homeomorphism, a sober space and a continuous map, then there exists a unique continuous map such that . Let be a -space, the injection of onto its sobrification . It is shown, here, that , where is the set of all locally closed points of . Some applications are also indicated. The Jacobson prime spectrum...
The complete real spectrum of a commutative ring with is introduced. Points of the complete real spectrum are triples , where is a real prime of , is a real valuation of the field and is an ordering of the residue field of . is shown to have the structure of a spectral space in the sense of Hochster [5]. The specialization relation on is considered. Special attention is paid to the case where the ring in question is a real holomorphy ring.
We prove a convenient equivalent criterion for monotone completeness of ordered fields of generalized power series with exponents in a totally ordered Abelian group G and coefficients in an ordered field F. This enables us to provide examples of such fields (monotone complete or otherwise) with or without integer parts, i.e. discrete subrings approximating each element within 1. We include a new and more straightforward proof that is always Scott complete. In contrast, the Puiseux series field...
Consider a compact subset of real -space defined by polynomial inequalities . For a polynomial non-negative on , natural sufficient conditions are given (in terms of first and second derivatives at the zeros of in ) for to have a presentation of the form , a sum of squares of polynomials. The conditions are much less restrictive than the conditions given by Scheiderer in [11, Cor. 2.6]. The proof uses Scheiderer’s main theorem in [11] as well as arguments from quadratic form theory...