2014/06/26 by Qing-Hu Hou, Hou, Qing-Hu, Rong-Hua Wang +1 · 2 citations
Computer Science · Mathematics · #33F10 #39A04 #68W30 #Advanced Differential Equations and Dynamical Systems #Classical Analysis and ODEs (math.CA) #Coding theory and cryptography #FOS: Computer and information sciences #FOS: Mathematics #Polynomial and algebraic computation #Symbolic Computation (cs.SC) #cs.SC #math.CA #msc:33F10 #msc:39A04 #msc:68W30
paper · pdf · doi:10.48550/arxiv.1408.2473
18 pages
arxiv created 2014/06/26 · openalex publication_date 2014/06/26 · arxiv updated 2014/08/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Let Δx f(x,y)=f(x+1,y)-f(x,y) and Δy f(x,y)=f(x,y+1)-f(x,y) be the difference operators with respect to x and y. A rational function f(x,y) is called summable if there exist rational functions g(x,y) and h(x,y) such that f(x,y)=Δx g(x,y) + Δy h(x,y). Recently, Chen and Singer presented a method for deciding whether a rational function is summable. To implement their method in the sense of algorithms, we need to solve two problems. The first is to determine the shift equivalence of two bivariate polynomials. We solve this problem by presenting an algorithm for computing the dispersion sets of any two bivariate polynomials. The second is to solve a univariate difference equation in an algebraically closed field. By considering the irreducible factorization of the denominator of f(x,y) in a general field, we present a new criterion which requires only finding a rational solution of a bivariate difference equation. This goal can be achieved by deriving a universal denominator of the rational solutions and a degree bound on the numerator. Combining these two algorithms, we can decide the summability of a bivariate rational function.