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Some results on generalized Cesàro stable of Janowski function

  • M. P. Jeyaraman,
  • T. G. Bhaskar

摘要

Let \(g_1\) g 1 and \(g_2 \) g 2 be any two analytic functions defined in the unit disc which are normalized by the condition \(g_1(0)=1=g_2(0)\) g 1 ( 0 ) = 1 = g 2 ( 0 ) and \(\sigma _n^{b-1,c}(z)\) σ n b - 1 , c ( z ) be the n th Cesàro mean of type \((b-1,c)\) ( b - 1 , c ) for \(1+b>c>0\) 1 + b > c > 0 . Then \(g_1\) g 1 is generalized Cesàro stable with respect to \(g_2\) g 2 , whenever \(\begin{aligned} \dfrac{\sigma _n^{b-1,c}(g_1,z)}{g_1(z)}\prec \dfrac{1}{g_2(z)}\quad \ (z \in \Delta ,\ n \in \mathbb {N}_0), \end{aligned}\) σ n b - 1 , c ( g 1 , z ) g 1 ( z ) 1 g 2 ( z ) ( z Δ , n N 0 ) , where \(\sigma _n^{b-1,c}(g,z) = \dfrac{1}{B_n} \sum _{j=0}^{n} B_{n-j} b_j z^j = \sigma _n^{b-1,c}(z) * g(z)\) σ n b - 1 , c ( g , z ) = 1 B n j = 0 n B n - j b j z j = σ n b - 1 , c ( z ) g ( z ) . The main aim of this article is to prove that \(\left( {(Az+1)}/{(Bz+1)}\right) ^\eta \) ( A z + 1 ) / ( B z + 1 ) η is generalized Cesàro stable with respect to \((1/(Bz+1)^{\eta })\) ( 1 / ( B z + 1 ) η ) but not with respect to itself for \(-1 \le B < A \le 0\) - 1 B < A 0 and \(0<\eta \le 1\) 0 < η 1 . As an application, we obtain new and existing results on Cesàro stability and stability.