Beiträge zur Algebra und Geometrie Contributions to Algebra and Geometry Vol. 51, No. 2, pp. 493507 (2010) 

Positivity theorems for solidangle polynomialsMatthias Beck, Sinai Robins and Steven V. SamDepartment of Mathematics, San Francisco State University, San Francisco, CA 94132, U.S.A. email: beck@math.sfsu.edu; Division of Mathematical Sciences, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, email: rsinai@ntu.edu.sg; Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A. email: ssam@math.mit.eduAbstract: For a lattice polytope $\P$, define $A_{\P}(t)$ as the sum of the solid angles of all the integer points in the dilate $t\P$. Ehrhart and Macdonald proved that $A_{\P}(t)$ is a polynomial in the positive integer variable $t$. We study the numerator polynomial of the solidangle series $\sum_{ t \ge 0 } A_\P(t) z^t$. In particular, we examine nonnegativity of its coefficients, monotonicity and unimodality questions, and study extremal behavior of the sum of solid angles at vertices of simplices. Some of our results extend to more general valuations. Keywords: solid angle, lattice polytope, Ehrhart polynomial, lattice points Classification (MSC2000): 28A75; 05A15, 52C07 Full text of the article (for subscribers):
Electronic version published on: 24 Jun 2010. This page was last modified: 8 Sep 2010.
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