On the zeros of solutions of certain linear differential equations

Suppose that the linear differential equation $$w^{(k)}(z)+{\mathop \sum^{k-2}\limits_{j=0}}A_{j}(z)w^{(j)}(z)=0$$ is such that the A_j are entire of finite order, and that A₀ is the dominant coefficient in terms of growth. The existence of a fundamental set of solutions each having few zeros is shown to imply that the order of A₀ is a positive integer.     

On zeros of solutions of higher order homogeneous linear differential equations

In this article, we investigate the exponent of convergence of zeros of solutions for some higher-order homogeneous linear differential equation, and prove that if A_k−1 is the dominant coefficient, then every transcendental solution f(z) of equation

f(k)+A_k-1 f(k-1)+?+A₀ f=0$f^{(k)}+A_{k-1}\hspace{0.17em}{f}^{(k-1)}+?+A_0\hspace{0.17em}f=0$

satisfies λ(f) = ∞, where λ(f) denotes the exponent of convergence of zeros of the meromorphic function f(z).     

On the distribution of zeros of solutions of first order delay differential equations

This paper contains new estimates for the distance between adjacent zeros of solutions of the first order delay differential equation

x^′(t)+p(t)x(t−τ)=0     

On oscillatory solutions of certain first order ordinary differential equations

By constructing a class of solutions to the integral inequality for t  t₀ large enough, where 0<A₁a(τ)A₂<+∞ and λ>1, that tend to zero as t→+∞ we address an open problem in the theory of nonlinear oscillations.     

On determining the location of complex zeros of solutions of certain linear differential equations

Summary We investigate the location of zeros of solutions for a class of second-order linear differential equations. This class had previously been investigated to determine the frequency of zeros of solutions AMS(MOS): 34A20.This research was supported in part by the National Science Foundation (DMS 84-20561).     

On zeros of solutions of linear differential equations

We consider linear differential equations with regular coefficients in $\text{¦ z ¦ < 1}$. We obtain sufficient conditions for all the solutions of these equations to vanish a given number of times at the most. First the results are obtained for differential equations of second order, then for differential equations of nth order, n > 2.     

On the behavior of solutions of certain differential equations of the fourth order

Summary In this paper three new results are obtained for equations of the form (1.1). Conditions are established which guarantee asymptotic stability, ultimate boundedness, and convergence of solutions of (1.1). This work was supported by the National Science Foundation COSIP (GY 4754). Entrata in Redazione il 12 ottobre 1970.     

On the convergence of solutions of certain systems of second order differential equations

Summary The object of this paper is to furnish an n-dimensional analogue of a convergence result obtained in [3] by Loud for the equation (1.4).     

一阶时滞微分方程解的零点分布

Abstract. The paper gives two estimates of the distance between adjacent zeros of solutions     

On the complex zeros of solutions of linear differential equations

Summary A classical result (see R.Nevanlinna, Acta Math.,58 (1932), p. 345) states that for a second-order linear differential equation, w + P(z) w + Q(z) w=0, where P(z) and Q(z) are polynomials, there exist finitely many rays, arg z=_j, for j=1,..., m, such that for any solution w=f(z) 0 and any > 0, all but finitely many zeros off lie in the union of the sectors ¦ arg z - _j¦ < for j=1,..., m. In this paper, we give a complete answer to the question of determining when the same result holds for equations of arbitrary order having polynomial coefficients. We prove that for any such equation, one of the following two properties must hold: (a) for any ray, arg z=, and any > 0, there is a solution f 0 of the equation having infinitely many zeros in the sector ¦arg z - ¦ <, or (b) there exist finitely many rays, arg z=_j, for j= 1,..., m, such that for any >0, all but finitely many zeros of any solution f 0 must lie in the union of the sectors ¦ arg z - _j¦ < for j=1, ..., m. In addition, our method of proof provides an effective procedure for determining which of the two possibilities holds for a given equation, and in the case when (b) holds, our method will produce the rays, arg z=_j. We emphasize that our result applies to all equations having polynomial coefficients, without exception. In addition, we mention that if the coefficients are only assumed to be rational functions, our results will still give precise information on the possible location of the bulk of the zeros of any solution.This research was supported in part by the National Science Foundation (DMS-84-20561 and DMS-87-21813).     

On periodic solutions of certain second order ordinary differential equations with periodic coefficients

Acta Mathematica Hungarica -