Abstract.
This paper extends previous works by Cassels-Ellison-Pfister and Christie in producing different collections of positive polynomials in ℝ[X,Y] which are not sums of three squares of rational fractions. The results are essentially obtained in extending methods of Galois descent for positivity of the ℝ(X)-rank of special kinds of elliptic curves.
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References
Artin, E.: Über die Zerlegung definiter Funktionen in Quadrate. Hamb. Abh. 5, 100–115 (1927)
Cassels, J.W.S., Ellison, W.J., Pfister, A.: On sums of squares and on elliptic curves over function fields. J. Number Theory 3, 125–149 (1971)
Christie, M.R.: Positive Definite Rational Functions of Two Variables Which Are Not the Sum of Three Squares. J. Number Theory 8, 224–232 (1976)
Colliot-Thélène, J.-L.: The Noether-Lefschetz theorem and sums of 4 squares in the rational function field R(x,y). Compositio 86, 235–243 (1993)
Hilbert, D.: Über die Darstellung definiter Formen als Summen von Formenquadraten. Math. Ann. 32, 342–350, (1888) = Ges. Abh. 2, pp. 154–164
Huisman, J., Mahé, L.: Geometrical aspects of the level of curves. J. Algebra 239, 647–674 (2001)
Knapp, A.: Elliptic curves. Math. Notes, Princeton U. Press, 1993
Lam, T.Y.: The algebraic theory of quadratic forms. Mathematics Lecture Note Series. W. A. Benjamin, Inc., 1973
S. Lang, Survey of diophantine geometry, Springer (1997)
Macé, O.: Sommes de trois carrés en deux variables et représentation de bas degré pour le niveau des courbes réelles, Thèse de l’Université de Rennes 1, 2000, http://tel.ccsd.cnrs.fr/documents/archives0/00/00/62/39/index_fr. html
Pfister, A.: Zur Darstellung definiter Funktionen als Summe von Quadraten. Invent. Math. 4, 229–237 (1967)
Silverman, J.H., Tate, J.: Rational points on elliptic curves. Undergraduate texts in mathematics, Springer-Verlag, 1992
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Macé, O., Mahé, L. Sommes de trois carrés de fractions en deux variables. manuscripta math. 116, 421–447 (2005). https://doi.org/10.1007/s00229-004-0535-0
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DOI: https://doi.org/10.1007/s00229-004-0535-0