Abstract
Let A A be an excellent ring. We show that if the real dimension of A A is at least three then A A has infinite Pythagoras number, and there exists a positive semidefinite element in A A which is not a sum of squares in A A .
Cite
CITATION STYLE
APA
Fernando, J., Ruiz, J., & Scheiderer, C. (2003). Sums of squares in real rings. Transactions of the American Mathematical Society, 356(7), 2663–2684. https://doi.org/10.1090/s0002-9947-03-03438-x
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