Available in electronic format
Available in print format
Proceedings of the American Mathematical Society
Proceedings of the American Mathematical Society
ISSN 1088-6826 (e) ISSN 0002-9939 (p)
     

Sums of squares over totally real fields are rational sums of squares

Author(s): Christopher J. Hillar
Journal: Proc. Amer. Math. Soc. 137 (2009), 921-930.
MSC (2000): Primary 12Y05, 12F10, 11E25, 13B24
Posted: September 25, 2008
Retrieve article in: PDF

Abstract | References | Similar articles | Additional information

Abstract: Let $ K$ be a totally real number field with Galois closure $ L$. We prove that if $ f \in \mathbb{Q}[x_1,\ldots,x_n]$ is a sum of $ m$ squares in $ K[x_1,\ldots,x_n]$, then $ f$ is a sum of

$\displaystyle 4m \cdot 2^{[L: \mathbb{Q}]+1} {[L: \mathbb{Q}] +1 \choose 2}$

squares in $ \mathbb{Q}[x_1,\ldots,x_n]$. Moreover, our argument is constructive and generalizes to the case of commutative $ K$-algebras. This result gives a partial resolution to a question of Sturmfels on the algebraic degree of certain semidefinite programming problems.


References:

1.
S. Burgdorf, Sums of Hermitian Squares as an Approach to the BMV Conjecture, preprint.

2.
M. D. Choi, Z. D. Dai, T. Y. Lam, B. Reznick, The Pythagoras number of some affine algebras and local algebras. J. Reine Angew. Math. 336 (1982), 45-82. MR 671321 (84f:12012)

3.
M.D. Choi, T. Y. Lam, B. Reznick, Even symmetric sextics, Math. Z. 195 (1987), no. 4, 559-580. MR 900345 (88j:11019)

4.
R. Elman, T. Y. Lam, Quadratic forms under algebraic extensions, Math. Ann. 219 (1976), 21-42. MR 0401649 (53:5476)

5.
M. Fiedler, Expressing a polynomial as the characteristic polynomial of a symmetric matrix, Lin. Alg. Appl. 141 (1990), 265-270. MR 1076118 (92b:15016)

6.
K. Gatermann, P. Parrilo, Symmetry groups, semidefinite programs, and sums of squares, J. Pure Applied Algebra 192 (2004), 95-128. MR 2067190 (2005d:68155)

7.
G. H. Golub, C. F. Van Loan, Matrix Computations, Johns Hopkins University Press, Baltimore, 1996. MR 1417720 (97g:65006)

8.
D. Hägele, Proof of the cases $ p \leq 7$ of the Lieb-Seiringer formulation of the Bessis-Moussa-Villani conjecture, J. Stat. Phys. 127 (2007), 1167-1171. MR 2331034 (2008c:82007)

9.
C. Hillar, Advances on the Bessis-Moussa-Villani Trace Conjecture, Lin. Alg. Appl. 426 (2007), 130-142. MR 2344564

10.
C. Hillar, J. Nie, An elementary and constructive solution to Hilbert's 17th problem for matrices, Proc. Amer. Math. Soc. 136 (2008), 73-76. MR 2350390

11.
R. Horn, C. R. Johnson, Matrix Analysis, Cambridge University Press, New York, 1985. MR 832183 (87e:15001)

12.
N. V. Ilyusheckin, Some identities for elements of a symmetric matrix, Journal of Mathematical Sciences 129 (2005), 3994-4008. MR 2037535 (2005a:15014)

13.
I. Klep, M. Schweighofer, Sums of hermitian squares and the BMV conjecture, J. Stat. Phys., to appear.

14.
T. Y. Lam, Introduction to Quadratic Forms over Fields, American Mathematical Society, 2004. MR 2104929 (2005h:11075)

15.
E. Landau, Uber die Darstellung definiter Funktionen durch Quadrate, Math. Ann. 62 (1906), 272-285. MR 1511376

16.
P. Landweber, E. Speer, On D. Hägele's approach to the Bessis-Moussa-Villani conjecture, preprint.

17.
J. Nie, K. Ranestad, B. Sturmfels, The algebraic degree of semidefinite programming, Mathematical Programming, to appear.

18.
A. Papachristodoulou, P. A. Parrilo, S. Prajna, Introducing SOSTOOLS: A General Purpose Sum of Squares Programming Solver, Proceedings of the IEEE Conference on Decision and Control (CDC), Las Vegas, NV, 2002.

19.
A. Papachristodoulou, P. A. Parrilo, S. Prajna, New Developments in Sum of Squares Optimization and SOSTOOLS, Proceedings of the American Control Conference (ACC), Boston, MA, 2004.

20.
P. Parrilo, Semidefinite programming relaxations for semialgebraic problems, Math. Program., Ser. B 96 (2003), 293-320. MR 1993050 (2004g:90075)

21.
P. Parrilo, Exploiting algebraic structure in sum of squares programs, Positive Polynomials in Control, Lecture Notes in Control and Information Sciences, Vol. 312, pp. 181-194, Springer, 2005. MR 2123524 (2005i:93038)

22.
P. Parrilo, H. Peyrl, A Macaulay $ 2$ package for computing sum of squares decompositions of polynomials with rational coefficients, SNC '07: Proceedings of the 2007 International Workshop on Symbolic-Numeric Computation, pp. 207-208, ACM, 2007.

23.
P. Parrilo, B. Sturmfels, Minimizing polynomial functions, Algorithmic and Quantitative Real Algebraic Geometry, DIMACS Series in Discrete Mathematics and Theoretical Computer Science, Vol. 60, pp. 83-99, Amer. Math. Soc., Providence, RI, 2003. MR 1995016 (2004e:13038)

24.
Y. Pourchet, Sur la représentation en somme de carrés des polynômes à une indéterminée sur un corps de nombres algébriques, Acta Arith. 19 (1971), 89-104. MR 0289442 (44:6632)

25.
V. Powers, T. Woermann, An algorithm for sums of squares of real polynomials, J. Pure and Appl. Alg. 127 (1998), 99-104. MR 1609496 (99a:11047)

26.
A. Prestel, C. N. Delzell, Positive Polynomials: From Hilbert's 17th Problem to Real Algebra, Springer, 2001. MR 1829790 (2002k:13044)

27.
B. Reznick, Uniform denominators in Hilbert's seventeenth problem, Math. Z. 220 (1995), 75-97. MR 1347159 (96e:11056)

28.
G. Schmeisser, A real symmetric tridiagonal matrix with a given characteristic polynomial, Lin. Alg. Appl. 193 (1993), 11-18. MR 1240269 (94i:15006)

29.
M. Schweighofer, Algorithmische Beweise für Nichtnegativ- und Positivstellensätze, Diplomarbeit an der Universität Passau, 1999.


Similar Articles:

Retrieve articles in Proceedings of the American Mathematical Society with MSC (2000): 12Y05, 12F10, 11E25, 13B24

Retrieve articles in all Journals with MSC (2000): 12Y05, 12F10, 11E25, 13B24


Additional Information:

Christopher J. Hillar
Affiliation: Department of Mathematics, Texas A\&M University, College Station, Texas 77843
Email: chillar@math.tamu.edu

DOI: 10.1090/S0002-9939-08-09641-X
PII: S 0002-9939(08)09641-X
Keywords: Rational sum of squares, semidefinite programming, totally real number field
Received by editor(s): June 11, 2007,
Received by editor(s) in revised form: March 31, 2008
Posted: September 25, 2008
Additional Notes: The author was supported under a National Science Foundation Postdoctoral Research Fellowship.
Communicated by: Bernd Ulrich
Copyright of article: Copyright 2008, American Mathematical Society


  AMS Website Logo Small Comments: webmaster@ams.org
© Copyright 2009, American Mathematical Society
Privacy Statement
Search the AMSPowered by Google