On the zeros of solutions of any order of derivative of second order linear differential equations taking small functions

Abstract

In this paper, we investigate the hyper-exponent of convergence of zeros of $f^{(j)}(z)-\varphi(z) (j\in N)$, where $f$ is a solution of second or $k(\geq2)$ order linear differential equation, $\varphi(z)\not\equiv0$ is an entire function satisfying $\sigma(\varphi)<\sigma(f)$ or $\sigma_{2}(\varphi)<\sigma_{2}(f)$. We obtain some precise results which improve the previous results in [3, 5] and revise the previous results in [11, 13]. More importantly, these results also provide us a method to investigate the hyper-exponent of convergence of zeros of $f^{(j)}(z)-\varphi(z)(j\in N)$.

Keywords

• linear differential equations
• hyper-order
• hyper-exponent of convergence of zeros