Sums of squares in real rings

被引：7

作者：

Fernando, JF ^{[1
]}

Ruiz, JM

Scheiderer, C

机构：

[1] Univ Complutense Madrid, Fac Ciencias Matemat, Dept Algebra, E-28040 Madrid, Spain

[2] Univ Complutense Madrid, Fac Ciencias Matemat, Dept Geometria & Topol, E-28040 Madrid, Spain

[3] Univ Duisburg, Fak 4, Inst Math, D-47048 Duisburg, Germany

来源：

TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY | 2004年 / 356卷 / 07期

关键词：

D O I：

10.1090/S0002-9947-03-03438-X

中图分类号：

O1 [数学];

学科分类号：

0701 ; 070101 ;

摘要：

Let A be an excellent ring. We show that if the real dimension of A is at least three then A has in finite Pythagoras number, and there exists a positive semidefinite element in A which is not a sum of squares in A.

引用

页码：2663 / 2684

页数：22

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