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On the Smallest and Largest Zeros of Müntz-Legendre Polynomials
Published online by Cambridge University Press: 20 November 2018
Abstract
Müntz-Legendre polynomials ${{L}_{n}}\left( \Lambda ;\,x \right)$ associated with a sequence $\Lambda \,=\,\left\{ {{\lambda }_{k}} \right\}$ are obtained by orthogonalizing the system $\left( {{x}^{{{\lambda }_{0}}}},{{x}^{{{\lambda }_{1}}}},{{x}^{{{\lambda }_{2}}}},... \right)$ in ${{L}_{2}}\left[ 0,1 \right]$ with respect to the Legendre weight. If the ${{\lambda }_{k}}\text{ }\!\!'\!\!\text{ s}$ are distinct, it is well known that ${{L}_{n}}\left( \Lambda ;\,x \right)$ has exactly $n$ zeros ${{l}_{n,n}}\,<\,{{l}_{n-1,n}}\,<\,\cdot \cdot \cdot \,<\,{{l}_{2,n}}\,<\,{{l}_{1,n}}$ on $\left( 0,1 \right)$.
First we prove the following global bound for the smallest zero,
An important consequence is that if the associated Müntz space is non-dense in ${{L}_{2}}\left[ 0,1 \right]$, then
so the elements ${{L}_{n}}\left( \Lambda ;\,x \right)$ have no zeros close to 0.
Furthermore, we determine the asymptotic behavior of the largest zeros; for $k$ fixed,
where ${{j}_{k}}$ denotes the $k$-th zero of the Bessel function ${{J}_{0}}.$
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- Copyright © Canadian Mathematical Society 2013