Skip to main content
Log in

Real fields, valuations, and quadratic forms

  • Published:
Manuscripta Mathematica Aims and scope Submit manuscript

Abstract

We study several field invariants arising in quadratic form theory. Some of the invariants considered are of particular interest in the study of real fields, including the length, the u-invariant, and the (reduced) stability index. In this context we give a systematic account of valuation theoretic arguments that lead to lower bounds for these invariants.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Similar content being viewed by others

References

  1. Arason J.K., Elman R.: Powers of the fundamental ideal in the Witt ring. J. Algebra 239, 150–160 (2001)

    Article  MathSciNet  MATH  Google Scholar 

  2. Becher K.J.: On fields of u-invariant 4. Arch. Math. 86, 31–35 (2006)

    Article  MathSciNet  MATH  Google Scholar 

  3. Becher K.J.: On the u-invariant of a real function field. Math. Ann. 346, 245–249 (2010)

    Article  MathSciNet  MATH  Google Scholar 

  4. Becher, K.J., Leep, D.B.: Pythagoras numbers and quadratic field extensions. Proceedings of the International Conference on the Algebraic and Arithmetic Theory of Quadratic Forms 2007, Lago Llanquihue (Chile). Contemp. Math. 493, 21–28 (2009)

  5. Becher K.J., Leep D.B.: The length and other invariants of a real field. Math. Z. 269, 235–252 (2011)

    Article  MathSciNet  MATH  Google Scholar 

  6. Becher, K.J., Leep, D.B.: The Elman–Lam–Krüskemper Theorem. ISRN Algebra. 2011, 106823 (2011). doi:10.5402/2011/106823

  7. Becker, E.: Hereditarily-Pythagorean fields and orderings of higher level. Monografias de Matemática 29, Instituto de matematica pura e aplicada, Rio de Janeiro (1978)

  8. Becker E., Köpping E.: Reduzierte quadratische Formen und Semiordnungen reeller Körper. Abh. Math. Sem. Univ. Hamburg 46, 143–177 (1977)

    Article  MathSciNet  MATH  Google Scholar 

  9. Bröcker L.: Zur Theorie der quadratischen Formen über formal reellen Körpern. Math. Ann. 210, 233–256 (1974)

    Article  MathSciNet  MATH  Google Scholar 

  10. Bröcker L.: Characterization of fans and hereditarily pythagorean fields. Math. Z. 151, 149–163 (1976)

    Article  MathSciNet  MATH  Google Scholar 

  11. Elman, R., Karpenko, N., Merkurjev, A.: The algebraic and geometric theory of quadratic forms 56. American Mathematical Society Colloquium Publications, Providence (2008)

  12. Elman R., Lam T.Y.: forms and the u-invariant, I. Math. Z. 131, 283–304 (1973)

    Article  MathSciNet  MATH  Google Scholar 

  13. Elman R., Lam T.Y.: Quadratic forms under algebraic extensions. Math. Ann. 219, 21–42 (1976)

    Article  MathSciNet  MATH  Google Scholar 

  14. Elman R., Prestel A.: Reduced stability of the Witt ring of a field and its Pythagorean closure. Am. J. Math. 106, 1237–1260 (1984)

    Article  MathSciNet  MATH  Google Scholar 

  15. Engler A.J., Prestel A.: Valued Fields. Springer Monographs. Springer, Berlin (2005)

    MATH  Google Scholar 

  16. Jacob B.: On the structure of pythagorean fields. J. Algebra 68, 247–267 (1981)

    Article  MathSciNet  MATH  Google Scholar 

  17. Knebusch M.: Specialization of quadratic and symmetric bilinear forms, and a norm theorem. Acta Arith. 24, 279–299 (1973)

    MathSciNet  MATH  Google Scholar 

  18. Krüskemper, M.: On annihilators in graded Witt rings and in Milnor’s K-theory. In: Jacob, W. B. et al. (eds.) Recent Advances in Real Algebraic Geometry and Quadratic Forms. Proceedings of the RAGSQUAD year 1990–1991, vol. 155, pp. 307–320. American Mathematical Society. Contemporary Mathematics, Berkeley (1994)

  19. Lam, T.Y.: Orderings, Valuations and Quadratic Forms. CBMS Regional Conference Series in Mathematics, vol. 52. American Mathematical Society, Providence (1983)

  20. Lam, T.Y.: Introduction to Quadratic Forms Over Fields. Graduate Studies in Mathematics, vol.67. American Mathematical Society, Providence (2005)

  21. Marshall M.: Some local global principles for formally real fields. Can. J. Math. 29, 606–614 (1977)

    Article  MATH  Google Scholar 

  22. Marshall M.: The Witt ring of a space of orderings. Trans. Am. Math. Soc. 258, 505–521 (1980)

    MATH  Google Scholar 

  23. Marshall, M.: Spaces of orderings and abstract real spectra. Lecture Notes in Mathematics, vol. 1636. Springer, Berlin (1996)

  24. Orlov D., Vishik A., Voevodsky V.: An exact sequence for \({K_{\ast}^{M}/2}\) with applications to quadratic forms. Ann. Math. 165, 1–13 (2007)

    Article  MathSciNet  MATH  Google Scholar 

  25. Pfister, A.: Quadratic forms with applications to algebraic geometry and topology. LMS Lecture Notes Series, vol. 217. Cambridge University Press, Cambridge (1995)

  26. Prestel, A.: Lectures on Formally Real Fields. Lecture Notes in Mathematics, vol. 1093. Springer, Berlin (1984)

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Karim Johannes Becher.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Becher, K.J., Leep, D.B. Real fields, valuations, and quadratic forms. manuscripta math. 141, 737–754 (2013). https://doi.org/10.1007/s00229-012-0597-3

Download citation

  • Received:

  • Revised:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00229-012-0597-3

Mathematics Subject Classification (2010)

Navigation