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Growth of solutions of second order linear differential equations

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This paper is devoted to studying the growth of solutions of equations of type f″+h(z)eazf′+Q(z)f=H(z) where h(z), Q(z) and H(z) are entire functions of order at most one. We prove four theorems of such type, improving previous results due to Gundersen and Chen.

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... The conditions on the coe‰cients of equation (1) have been studied so that all solutions of (1) are of infinite order [2,16,17]. In [7,8,9,10,11], certain conditions have been established on the coe‰cients of associated homogeneous di¤erential equation (2) for the existence of non-trivial solutions of infinite order. ...
... The following lemma proved by Wang and Laine [17] provides an estimate for an entire function f in the neighbourhood of the points in which f takes the maximum modulus. ...
... Case (b). Let dðP; y 0 Þ < 0. Again, as dðP; yÞ is a continuous function, therefore 3 2 dðP; y 0 Þ < dðP; y k Þ < 1 2 dðP; y 0 Þ solutions of non-homogeneous linear differential equations for all su‰ciently large k A N. Using part (ii) of Lemma 2, we have exp 3ð1 þ eÞ 2 dðP; y 0 Þr n k a jAðr k e iy k Þj a exp ð1 À eÞ 2 dðP; y 0 Þr n k ð24Þ for all su‰ciently large k A N. Using equations (1), (17), (19) and (24), we obtain jBðr k e iy k Þj a f 00 ðr k e iy k Þ f ðr k e iy k Þ þ jAðr k e iy k Þj ...
... Á 0/ are meromorphic functions of finite order. Some results on the growth of entire solutions of (1.1) have been obtained by several researchers (see [5,6,12,14]). Li and Wang (see [12]) investigated the nonhomogeneous linear differential equation ...
... < 1 2 ; and b is a real constant. They proved that all nontrivial solutions of (1.2) are of infinite order, provided that .H / < 1: After their, Wang and Laine (see [14]) studied the differential equation ...
... [14]). Suppose that A 0 6 Á 0; A 1 6 Á 0; H are entire functions of order less than one, and the complex constants a; b satisfy ab ¤ 0 and a ¤ b: Then every nontrivial solution f of (1.3) is of infinite order.J. ...
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This paper is devoted to studying the growth and oscillation of solutions and their derivatives of equations of the type f 00 C A .´/ f 0 C B .´/ f D F .´/ ; where A .´/ ; B .´/ .6 Á 0/ and F .´/ .6 Á 0/ are meromorphic functions of finite order.
... Recently, some mathematicians investigate the non-homogeneous equations of second order and higher order linear equations such as Li and Wang [18], Cao [5], Wang and Laine [22] and proved that every solution of these equation has infinite order. ...
... In 2008, Wang and Laine [22] investigated the non-homogeneous equation related to (2) and obtained the following result. ...
... Theorem C(see. [22,Theorem 1.1]) Suppose that A j ≡ 0(j = 0, 1), H are entire functions of order less than one, and the complex constants a, b satisfy ab = 0 and a = b. ...
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In this paper, we deal with the order of growth and the hyper order of solutions of higher order linear differential equations where Bj (z) (j = 0, 1, ..., k - 1) and F are entire functions or polynomials. Some results are obtained which improve and extend previous results given by Z.-X. Chen, J. Wang, T.-B. Cao and C.-H. Li.
... Ilpo and Steve proved several results concerning the particular cases when A(z) is either a polynomial or a rational function in (3.5); see [2], [4]. In [3] they investigated equation (3.1) when A(z) is an entire periodic function. The next theorem is one example of their many results of this type and equation (3.4) was used in the proof. ...
... Theorem 3.4 ([3]). Consider equation (3.1) ...
... Equation (3.7) has been studied by several authors. Theorem 3.5 ([3] ...
... In [19], Wang and Laine have investigated the growth of solutions of some second order non-homogenous linear differential equations and have obtained the following result. ...
... Theorem 1.5. [19] Let A j (z) (̸ ≡ 0) (j = 0, 1) and H (z) be entire functions with max{ρ (A j ) (j = 0, 1) , ρ (H)} < 1, and let a, b be complex constants that satisfy ab ̸ = 0 and a ̸ = b. Then every non-trivial solution f of the equation Thus, the following question arises naturally: Whether the results similar to Theorem 1.5 can be obtained if ρ(H) = 1? ...
... Kumar and Saini [8] consider λ(A) < ρ(A) and B(z) a transcendental entire function satisfying either ρ(B) = ρ(A) or B(z) having Fabry gap and proved that non-trival solutions of (1) are of infinite order. J. Wang and I. Laine [12] consider A(z) = h(z)e −z and B(z) to satisfy ...
... Theorem A [12] Suppose that A(z) and B(z) are entire functions where A(z) = h(z)e −z and ρ(h) < ρ(B) = 1, and that B(z) satisfies (2) in a set of positive upper logarithmic density. Then every non-trivial solution f of equation (1) is of infinite order. ...
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In this paper, we will prove that all non-trivial solutions of f+A(z)f+B(z)f=0f''+A(z)f'+B(z)f=0 are of infinite order, where we have some restrictions on entire functions A(z) and B(z).
... Here, we employ two results to handle this proposition, the first one is due to Wang and Laine [25,Lemma 2.4], the latter one is due to Gundersen [9, Corollary 2]. ...
... It is related to a famous differential equation question posed by Gundersen in [11]. We refer to [6,10,25] for some results of the above differential equation. It is natural to generalize the above differential equation to f + Π 1 (z)e az f + Π 2 e bz f = Π 3 , where the infinite product Π i is defined as in the main theorem. ...
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The paper is mainly devoted to deriving the relationship between an entire function and its derivative when they share one small function except possibly a set, which is related to the famous Brück conjecture. In addition, two propositions of infinite products are obtained. The first one is the growth property of a certain infinite product. The second one is the property of entire solutions of the differential equation which concerns infinite products.
... Recently in [14], Wang and Laine have investigated the growth of solutions of some second order linear differential equations and have obtained. ...
... Theorem 3 (see [14]). Let A j (z) ( ≡ 0) (j = 0, 1) and F (z) be entire functions with max{ρ (A j ) (j = 0, 1) , ρ (F )} < 1, and let a, b be complex constants that satisfy ab = 0 and a = b. ...
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This paper is devoted to studying the growth and the oscillation of solutions of the second-order nonhomogeneous linear differential equation f '' +A 1 (z)e P(z) f ' +A 0 (z)e Q(z) f=F, where P(z),Q(z) are nonconstant polynomials such that deg P = deg Q = n and A j (z)(¬≡0) for j=0,1 and F(z) are entire functions with max{ρ(A j ):j=0,1}<n. We also investigate the relationship between small functions and differential polynomials g f (z)=d 2 f '' +d 1 f ' +d 0 f, where d 0 (z),d 1 (z),d 2 (z) are entire functions such that at least one of d 0 ,d 1 ,d 2 does not vanish identically with ρ(d j )<n for j=0,1,2 generated by solutions of the above equation.
... In[10], Wang and Laine investigated the growth of solutions of some second order nonhomogeneous linear differential equation and obtained. Theorem A([10]). ...
... In[10], Wang and Laine investigated the growth of solutions of some second order nonhomogeneous linear differential equation and obtained. Theorem A([10]). Let A j (z) ( ≡ 0) (j = 0, 1) and F (z) be entire functions with max{σ (A j ) (j = 0, 1) , σ (F )} < 1, and let a, b be complex constants that satisfy ab = 0 and a = b. ...
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In this paper, we study the order of growth of solutions to the non-homogeneous linear differential equation az}f
... Wang and Laine investigated the nonhomogeneous equation (4) and got the following; see [7]. ...
... Lemma 6 (see [7]). ...
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We prove that the hyperorder of every nontrivial solution of homogenous linear differential equations of type and nonhomogeneous equation of type is one, where are entire functions of order less than one, improving the previous results of Chen, Wang, and Laine.
... The general problem of Ozawa has been proposed by Heittokangas, and given by Gundersen, see [10,Section 5]. More and more papers focus on the existence of finite order solutions of second linear differential equations (1.3) with entire coefficients, even precise form of finite order solutions, see [14,15,17,24,36,39]. ...
... The general problem of Ozawa has been proposed by Heittokangas, and given by Gundersen, see [10,Section 5]. More and more papers focus on the existence of finite order solutions of second linear differential equations (1.3) with entire coefficients, even precise form of finite order solutions, see [14,15,17,24,36,39]. ...
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We show a necessary and sufficient condition on the existence of finite order entire solutions of linear differential equations f^{(n)}+a_{n-1}f^{(n-1)}+\cdots+a_1f'+a_0f=0,\eqno(+) where aia_i are exponential sums for i=0,,n1i=0,\ldots,n-1 with all positive (or all negative) rational frequencies and constant coefficients. Moreover, under the condition that there exists a finite order solution of (+) with exponential sum coefficients having rational frequencies and constant coefficients, we give the precise form of all finite order solutions, which are exponential sums. It is a partial answer to Gol'dberg-Ostrovski\v{i} Problem and Problem 5 in \cite{HITW2022} since exponential sums are of completely regular growth.
... We are motivated by Theorem E and replace the condition of B(z) to satisfy some conditions given in Theorem 3. The following Lemma yield us a lower bound for modulus of an entire function in the neighbourhood of θ, where θ ∈ [0, 2π). Lemma 8. [23] Suppose f (z) is an entire function of finite order ρ and M (r, f ) = |f (re ιθr )| for every r. Given ζ > 0 and 0 < C(ρ, ζ) < 1, there exists 0 < l 0 < 1 2 and a set S ⊂ (1, ∞) with log dens(S) ≥ 1 − ζ such that ...
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In this article, we study about the solutions of second order linear differential equations by considering several conditions on the coefficients of homogenous linear differential equation and its associated non-homogenous linear differential equation.
... In several papers like [12], [14], [15], [21] and [23] authors have considered A(z) = h(z)e P (z) , where P (z) is a polynomial of degree n satisfying λ(A) < ρ(A) and B(z) with various conditions. Here we have exchanged the conditions of A(z) with B(z) and prove the following result. ...
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Considering differential equation f''+A(z)f'+B(z)f=0, where A(z) and B(z) are entire complex functions, our results revolve around proving all non-trivial solutions are of infinite order taking various restrictions on coefficients A(z) and B(z).
... Wang and Laine [8] have established that when ρ(A) = ρ(B) and ρ(H) < max{ ρ(A), ρ(B)} , then all solutions of equation (1) are of infinite order. In our case we have assumed ρ(A) = ρ(B) and proved the following theorem: ...
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In this paper, we have considered second order non-homogeneous linear differential equations having entire coefficients. We have established conditions ensuring non-existence of finite order solution of such type of differential equations.
... Proof. Following the argument in [18,Lemma 2.4] and Lemma 2, we obtain ...
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We investigate transcendental entire solutions of complex differential equations f″+A(z)f=H(z), where the entire function A(z) has a growth property similar to the exponential functions, and H(z) is an entire function of order less than that of A(z). We first prove that the lower order of the entire solution to the equation is infinity. By using our result on the lower order, we prove the entire solution does not bear any Baker wandering domains.
... The proof deviates from that of [8, Theorem 6] in the sense that we make use of [2], which is not needed in proving [8, Theorem 6]In the remaining results the functions T (r, A) and log M (r, A) are asymptotically comparable, where A(z) is the coefficient function in (2). Prior to Theorem D, the same conclusion was proved under the stronger assumptions that ρ(B) < ρ(A) < ∞ and T (r, A) ∼ log M (r, A) as r → ∞ outside of a set of finite logarithmic measure, see [16]. Next we state an analogous result involving the lower order and a class of entire functions A(z) satisfying T (r, A) ∼ α log M (r, A), r → ∞, ...
... The problem of finding conditions on A(z) and B (z) for the case ρ(A) ≥ ρ(B ) under which all nontrivial solutions of (1.1) are of infinite order has raised considerable interest, and many parallel results on this question written after Theorem A, see, for example, [3,4,14,15,17,18,22]. It would be interesting to get some relations between the growth of solutions of (1.1) and some deep results in Nevanlinna theory of meromorphic functions. ...
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... holds for all m ≥ 0 and all r / ∈ F . Ä ÑÑ 2.6º (see [23]) Let f (z) be an entire function of finite order ρ, and M (r, f ) = f (re iθ r ) for every r. Given ζ > 0 and 0 < C(ρ, ζ) < 1, there exists a constant 0 < l 0 < 1 2 and a set E ζ of lower logarithmic density greater than 1 − ζ such that ...
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... What can we have if there exists one middle coefficient í µí°´íµí°´í µí±‘ (í µí± §) (1 ≤ í µí±‘ ≤ í µí±˜−1) such that í µí°´íµí°´í µí±‘ (í µí± §) grows faster than other coefficients in (12) or (13)? Many authors have investigated this question when í µí°´íµí°´í µí±‘ (í µí± §) is of finite order and obtained many results (e.g., see131415). Here, our question is that under what conditions can we obtain similar results with Theorems B-C if í µí°´íµí°´í µí±‘ (í µí± §) (1 ≤ í µí±‘ ≤ í µí±˜ − 1) is of finite iterated order and grows faster than other coefficients in (12) or (13). ...
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... Chen [3] got the same conclusion when a cb c > 1 , and Chen and Shon [5] investigated the more general equations with meromorphic coefficients. Under the same assumption of Theorem A, if A 1 z and A 0 z are meromorphic functions with σ A j < 1 j 0, 1 , then there is the same conclusion with Theorem A. In 2008, Wang and Laine [6] extended Theorem A to nonhomogeneous second-order linear differential equations. ...
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... Our paper is motivated by the papers [11,12]. In these papers, the authors considered the special differential equation, f + A 1 (z)e P 1 (z) f + A 0 (z)e P 0 (z) f = 0, (4.5) ...
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Book
1 Basic Nevanlinna theory.- 2 Unicity of functions of finite (lower) order.- 3 Five-value, multiple value and uniqueness.- 4 The four-value theorem.- 5 Functions sharing three common values.- 6 Three-value sets of meromorphic functions.- 7 Functions sharing one or two values.- 8 Functions sharing values with their derivatives.- 9 Two functions whose derivatives share values.- 10 Meromorphic functions sharing sets.
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Synopsis We show that if B(z) is either (i) a transcendental entire function with order (B) ≠1, or (ii) a polynomial of odd degree, then every solution f ≠0 to the equation f ″ + e −z f ′ + B(z)f = 0 has infinite order. We obtain a partial result in the case when B(z) is an even degree polynomial. Our method of proof and lemmas for case (i) of the above result have independent interest.
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This paper investigates the growth of solutions of the equation f″ + e-z f′ + Q(z)f = 0 where the order (Q) = 1. When Q(z) = h(z)ebz, h(z) is nonzero polynomial, b ≠ - 1 is a complex constant, every solution of the above equation has infinite order and the hyper-order 1. We improve the results of M. Frei, M. Ozawa, G. Gundersen and J. K. Langley.
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It is shown that if Q(z) is a non-constant polynomial, then all non-trivial solutions of y"+ (ez + Q(z))y = 0 have zeros with infinite exponent of convergence. Similar methods are used to settle a problem of M. Ozawa: if P(z) is a non-constant polynomial, all non-trivial solutions of y"+e-zy' + P(z)y = 0 have infinite order.
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On a solution of w&amp;Prime;+e - zw'+(az+b)w=0, Kodai math
  • M Ozawa
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