Abstract
Fork=1, 2,... letj vk andc vk be thek-th positive zeros of the Bessel function
whereY v (X) is the Bessel function of the second kind. Using the notationj vκ =C vk withκ=k−α/π introduced in [3] we show that the functionj vκ +f(v) is convex with respect toυ≥0 forκ≥0.7070..., wheref(υ) is defined in the theorem of section 2. As an application we find the inequality 0 >j 0κ +j 1κ − 2κπ > log 8/9, where κ≥0.7070....
Sunto
Perk=1,2,..., sianoj vk ec vk rispettivamente ilk-esimo zero della funzione di BesselJ v (X) di prima specie e della funzione cilindrica
doveY v (X) rappresenta la funzione di Bessel di seconda specie. Usando la notazionejC vκ con κ =k−α/π, introdotta in [3], si dimostra che la funzionej vκ +f(v) é convessa rispetto aυ≥0 perκ≥0.7070..., dovef(υ) é definita nel teorema del par. 2. Come applicazione troviamo la doppia disuguaglianza 0 >j 0κ +j 1κ − 2κπ > log 8/9, dove κ≥0.7070....
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Elbert, Á., Laforgia, A. A convexity property of zeros of Bessel functions. Z. angew. Math. Phys. 41, 734–737 (1990). https://doi.org/10.1007/BF00946105
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DOI: https://doi.org/10.1007/BF00946105