RT Journal Article T1 Supremum Norms for 2-Homogeneous Polynomials on Circle Sectors A1 Muñoz-Fernández, Gustavo A. A1 Pellegrino, D. A1 Seoane-Sepúlveda, Juan B. A1 Weber, A. AB We consider the Banach space of two homogeneous polynomials endowed with the supremum norm parallel to . parallel to(D(beta)) over circle sectors D(beta) of angle beta for several values of beta is an element of [0, 2 pi]. We provide an explicit formula for parallel to . parallel to(D(beta)), a full description of the extreme points of the corresponding unit balls, and a parametrization and a plot of their unit spheres. This work is an extension of a series of papers on the same topic published in the last decade and it has a number of applications to obtain polynomial-type inequalities PB Heldermann Verlag SN 0944-6532 YR 2014 FD 2014 LK https://hdl.handle.net/20.500.14352/33759 UL https://hdl.handle.net/20.500.14352/33759 LA eng NO [1] R. M. Aron, M. Klimek: Supremum norms for quadratic polynomials, Arch. Math.76 (2001) 73–80.[2] L. Białas-Cie˙z, P. Goetgheluck: Constants in Markov’s inequality on convex sets,East J. Approx. 1(3) (1995) 379–389.[3] Y. S. Choi, S. G. Kim: The unit ball of P(2l2 2), Arch. Math. 71(6) (1998) 472–480.[4] Y. S. Choi, S. G. Kim: Smooth points of the unit ball of the space P(2l1), Results Math. 36 (1999) 26–33.[5] Y. S. Choi, S. G. Kim: Exposed points of the unit balls of the spaces P(2l2 p) (p = 1, 2,∞), Indian J. Pure Appl. Math. 35 (2004) 37–41.[6] J. L. G´amez-Merino, G. A. Muñoz-Fernandez, V. M. Sanchez, J. B. Seoane-Sepulveda: Inequalities for polynomials on the unit square via the Krein-Milman Theorem, J. Convex Analysis 20(1) (2013) 125–142.[7] B. C. Grecu: Geometry of homogeneous polynomials on two-dimensional real Hilbert spaces, J. Math. Anal. Appl. 293(1) (2004) 578–588.[8] B. C. Grecu: Extreme 2-homogeneous polynomials on Hilbert spaces, Quaest. Math. 25(4)(2002) 421–435.[9] B. C. Grecu: Geometry of 2-homogeneous polynomials on lp spaces, 1 < p < ∞, J. Math. Anal. Appl. 273(1) (2002)262–282.[10] B. C. Grecu: Smooth 2-homogeneous polynomials on Hilbert spaces, Arch. Math. 76(6) (2001) 445–454.[11] B. C. Grecu: Geometry of three-homogeneous polynomials on real Hilbert spaces,J. Math. Anal. Appl. 246(1) (2000) 217–229.[12] B. C. Grecu, G. A. Muñoz-Fernandez, J. B. Seoane-Sepulveda: The unit ball of the complex P(3H), Math. Z. 263 (2009) 775–785.[13] B. C. Grecu, G. A. Muñoz-Fern´andez, J. B. Seoane-Sepulveda: Unconditional constants and polynomial inequalities, J. Approx. Theory 161(2) (2009) 706–722.[14] A. G. Konheim, T. J. Rivlin: Extreme points of the unit ball in a space of real polynomials, Amer. Math. Monthly 73 (1966) 505–507.[15] L. Milev, S. G. Revesz: Bernstein’s inequality for multivariate polynomials on the standard simplex,J.Inequal. Appl. 2005(2) (2005) 145–163.[16] L. Milev, N. Naidenov: Strictly definite extreme points of the unit ball in a polynomial space, C. R. Acad. Bulg. Sci. 61 (2008) 1393–1400.[17] L. Milev, N. Naidenov: Indefinite extreme points of the unit ball in a polynomial space, Acta Sci. Math. 77 (2011) 409–424.[18] G. A. Muñoz-Fernandez, D. Pellegrino, J. Ramos Campos, J. B. Seoane-Sep´ulveda: On the optimality of the hypercontractivity of the complex Bohnenblust-Hille inequality,arXiv:1301.1539 (2013).[19] G. A. Muñoz-Fernandez, S. G. Revesz, J. B. Seoane-Sepulveda: Geometry of homogeneous polynomials on non symmetric convex bodies, Math. Scand. 105 (2009)147–160.[20] G. A. Muñoz-Fernandez, V. M. S´anchez, J. B. Seoane-Sep´ulveda: Estimates on the derivative of a polynomial with a curved majorant using convex techniques, J.Convex Analysis 17(1) (2010) 241–252.[21] G. A. Muñoz-Fern´andez, V. M. Sanchez, J. B. Seoane-Sepulveda: Lp-analogues of Bernstein and Markov inequalities, Math. Inequal. Appl. 14(1) (2011) 135–145.[22] G. A. Muñoz-Fernandez, Y. Sarantopoulos: Bernstein and Markov-type inequalities for polynomials in real Banach spaces, Math. Proc. Camb. Philos. Soc. 133 (2002) 515–530.[23] G. A. Muñoz-Fernandez, Y. Sarantopoulos, J. B. Seoane-Sepulveda: An application of the Krein-Milman theorem to Bernstein and Markov inequalities, J. Convex Analysis 15 (2008) 299–312.[24] G. A. Muñoz-Fernandez, J. B. Seoane-Sepulveda:Geometry of Banach spaces of Trinomials, J. Math. Anal. Appl. 340 (2008) 1069–1087.[25] D. Nadzhmiddinov, Yu. N. Subbotin: Markov inequalities for polynomials on triangles,Mat. Zametki 46(2) (1989) 76–82, 159 (in Russian); Math. Notes 46(2)(1989) 627–631 (in English).[26] S. Neuwirth: The maximum modulus of a trigonometric trinomial, J. Anal. Math.104 (2008) 371–396.[27] D. R. Wilhelmsen: A Markov inequality in several dimensions, J. Approx. Theory 11 (1974) 216–220. NO CNPq NO INCT-Matematica DS Docta Complutense RD 29 abr 2024