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November 2004



This work is a self-contained treatise on the research conducted on squares by Pfister, Hilbert, Hurwitz, and others. Many classical and modern results and quadratic forms are brought together in this book, and the treatment requires only a basic knowledge of rings, fields, polynomials, and matrices. The author deals with many different approaches to the study of squares, from the classical works of the late nineteenth century, to areas of current research.


1. The theorem of Hurwitz; 2. The 2n theorems and the Stufe of fields; 3. Examples of the Stufe of fields and related topics; 4. Hilbert's 17th problem; 5. Positive definite functions and sums of squares; 6. An introduction to Hilbert's theorem; 7. The two proofs of Hilbert's theorem; 8. Theorems of Reznick and Choi, Lam and Reznick; 9. Theorems of Choi, Calderon and Robinson; 10. The theorem of Hurwitz-Radon; 11. An introduction to quadratic form theory; 12. The theory of multiplicative forms and Pfister forms; 13. The Hopf condition; 14. Examples of bilinear identities and a theorem of Gabel; 15. Artin-Schreier theory of formally real fields; 16. Squares and sums of squares in fields and their extension fields; 17. Pourchet's theorem and related results; 18. Examples of the Stufe and Pythagoras number of fields using the Hasse-Minkowski theorem; Appendix: Reduction of matrices to canonical form.


"A well-written, unpretentious introduction to squares and sums of squares in fields." American Mathematical Monthly "...Rajwade's richly detailed: the reader is not forced to reproduce complicated algebraic calculations just to follow the arguments. Even more delightful is how Rajwade approaches the frontiers of current research in certain aspects of the algebraic theory of quadratic forms without significantly increasing demands on the reader! Highly recommended." D.V. Feldman, Choice "Anyone wanting to learn something about the algebraic theory of quadratic forms will find this book useful. It is written at an elementary level, accessible to undergraduate students. At the same time, it contains several important topics, including the classical theorems of Hilbert, Hurwitz and Radon, not covered in the standard references." Murray Marshall, Mathematical Reviews "...this book includes beautiful and important mathematics which can be explained at a fairly elementary level. Many of these theorems have appeared only in research journals and certainly deserve to be advertised in expository books and appreciated by a wide audience." Daniel B. Shapiro, The American Mathematical Monthly
EAN: 9780521426688
ISBN: 0521426685
Untertitel: 'Cambridge Studies in Italian H'. Sprache: Englisch.
Erscheinungsdatum: November 2004
Seitenanzahl: 300 Seiten
Format: kartoniert
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