Using sums of squares to prove that certain entire functions have only real zeros

George Gasper Jr

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Using sums of squares to prove that certain entire functions have only real zeros

George Gasper Jr

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Abstract

It is shown how sums of squares of real valued functions can be used to give new proofs of the reality of the zeros of the Bessel functions $J_\alpha (z)$ when $\alpha \ge -1,$ confluent hypergeometric functions ${}_0F_1(c\/; z)$ when $c>0$ or $0>c>-1$, Laguerre polynomials $L_n^\alpha(z)$ when $\alpha \ge -2,$ and Jacobi polynomials $P_n^{(\alpha,\beta)}(z)$ when $\alpha \ge -1$ and $ \beta \ge -1.$ Besides yielding new inequalities for $|F(z)|^2,$ where $F(z)$ is one of these functions, the derived identities lead to inequalities for $\partial |F(z)|^2/\partial y$ and $\partial ^2 |F(z)|^2/\partial y^2,$ which also give new proofs of the reality of the zeros.

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BibTeX RIS

George Gasper Jr. 1993-07-09. Using sums of squares to prove that certain entire functions have only real zeros. https://arxiv.org/abs/math/9307210

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