Abstract
Let E be a subspace of C(X) and define R(E):={g/h: g,hεE;h>0}. We prove that R(E) is dense in C(X) if for every X 0⊂X there exists xεX 0 such that E contains an approximation to a δ-function at the point x on the set X 0. We use this principle to study the density of Müntz rationals in two variables.
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Shekhtman, B. On the density principle for rational functions. Numerical Algorithms 25, 341–346 (2000). https://doi.org/10.1023/A:1016669325910
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DOI: https://doi.org/10.1023/A:1016669325910