1. Universal lex ideal approximations of extended Hilbert functions and Hamilton numbers.
- Author
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Ananyan, Tigran and Hochster, Melvin
- Subjects
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POLYNOMIAL rings , *HILBERT functions , *NUMBER theory , *POLYNOMIALS - Abstract
Let R (h) denote the polynomial ring in variables x 1 , ... , x h over a specified field K. We consider all of these rings simultaneously, and in each use lexicographic (lex) monomial order with x 1 > ⋯ > x h. Given a fixed homogeneous ideal I in R (h) , for each d there is unique lex ideal generated in degree at most d whose Hilbert function agrees with the Hilbert function of I up to degree d. When we consider I R (N) for N ≥ h , the set B d (I , N) of minimal generators for this lex ideal in degree at most d may change, but B d (I , N) is constant for all N ≫ 0. We let B d (I) denote the set of generators one obtains for all N ≫ 0 , and we let b d = b d (I) be its cardinality. The sequences b 1 , ... , b d , ... obtained in this way may grow very fast. Remarkably, even when I = (x 1 2 , x 2 2) , one obtains a very interesting sequence, 0 , 2 , 3 , 4 , 6 , 12 , 924 , 409620 , .... This sequence is the same as H d − 1 + 1 for d ≥ 2 , where H d is the d th Hamilton number. The Hamilton numbers were studied by Hamilton and by Hammond and Sylvester because of their occurrence in a counting problem connected with the use of Tschirnhaus transformations in manipulating polynomial equations. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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