• Differential sobordination and Bazilevič functions

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    • Keywords


      Differential subordination; univalent; starlike and convex functions

    • Abstract


      LetM(z)=zn+…,N(z)=zn+… be analytic in the unit disc Δ and let λ(z)=N(z)/zN′(z). The classical result of Sakaguchi-Libera shows that Re(M′(z)/N′(z))<0 implies Re(M(z)/N(z))>0 in Δ whenever Re(λ(z))>0 in Δ. This can be expressed in terms of differential subordination as follows: for anyp analytic in Δ, withp(0)=1,p(z)+λ(z)zp′(z)<1+z/1−z impliesp(z)<1+z/1−z, for Reλ(z)>0,z∈Δ.

      In this paper we determine different type of general conditions on λ(z),h(z) and ϕ(z) for which one hasp(z)+λ(z)zp′(z)<h(z) impliesp(z)<ϕ(z)<h(z) z∈Δ. Then we apply the above implication to obtain new theorems for some classes of normalized analytic funotions. In particular we give a sufficient condition for an analytic function to be starlike in Δ.

    • Author Affiliations


      S Ponnusamy1 2

      1. School of Mathematics, SPIC Science Foundation, 92, G. N. Chetty Road, Madras - 600 017, India
      2. Department of Mathematics, University of Helsinki, Hallituskatu 15, PO Box 4, Helsinki - FIN 00014, Finland
    • Dates

  • Proceedings – Mathematical Sciences | News

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      Posted on July 25, 2019

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