On points at infinity of real spectra of polynomial rings

نویسنده

  • F. Lucas
چکیده

Let R be a real closed field and A = R[x1, . . . , xn]. Let Sper A denote the real spectrum of A. There are two kinds of points in Sper A: finite points (those for which all of |x1|,. . . ,|xn| are bounded above by some constant in R) and points at infinity. In this paper we study the structure of the set of points at infinity of Sper A and their associated valuations. Let T be a subset of {1, . . . , n}. For j ∈ {1, . . . , n}, let yj = xj if j∈/T and yj = 1 xj if j ∈ T . Let BT = R[y1, . . . , yn]. We construct a finite partition Sper A = ∐ T UT and a homeomorphism of each of the sets UT with a subspace of the space of finite points of Sper BT . For each point δ at infinity in UT , we describe the associated valuation νδ∗ of its image δ ∗ ∈ Sper BT in terms of the valuation νδ associated to δ. Among other things we show that the valuation νδ∗ is composed with νδ (in other words, the valuation ring Rδ is a localization of Rδ∗ at a suitable prime ideal).

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Spectrum of plane curves via knot theory

In this paper, we use topological methods to study various semicontinuity properties of the local spectrum of singular points of algebraic plane curves and spectrum at infinity of polynomial maps in two variables. Using the Seifert form, the Tristram–Levine signatures of links, and the associated Murasugi-type inequalities, we reprove (in a slightly weaker form) a result obtained by Steenbrink ...

متن کامل

On constant products of elements in skew polynomial rings

Let $R$ be a reversible ring which is $alpha$-compatible for an endomorphism $alpha$ of $R$ and $f(X)=a_0+a_1X+cdots+a_nX^n$ be a nonzero skew polynomial in $R[X;alpha]$. It is proved that if there exists a nonzero skew polynomial $g(X)=b_0+b_1X+cdots+b_mX^m$ in $R[X;alpha]$ such that $g(X)f(X)=c$ is a constant in $R$, then $b_0a_0=c$ and there exist nonzero elements $a$ and $r$ in $R$ such tha...

متن کامل

On strongly J-clean rings associated with polynomial identity g(x) = 0

In this paper, we introduce the new notion of strongly J-clean rings associated with polynomial identity g(x) = 0, as a generalization of strongly J-clean rings. We denote strongly J-clean rings associated with polynomial identity g(x) = 0 by strongly g(x)-J-clean rings. Next, we investigate some properties of strongly g(x)-J-clean.

متن کامل

On annihilator ideals in skew polynomial rings

This article examines annihilators in the skew polynomial ring $R[x;alpha,delta]$. A ring is strongly right $AB$ if everynon-zero right annihilator is bounded. In this paper, we introduce and investigate a particular class of McCoy rings which satisfy Property ($A$) and the conditions asked by P.P. Nielsen. We assume that $R$ is an ($alpha$,$delta$)-compatible ring, and prove that, if $R$ is ni...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2007