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Circular symmetrization,subordination and arclength problems on convex functions
Authors:M Okada  S Ponnusamy  A Vasudevarao  H Yanagihara
Institution:1. Department of Applied Science, Faculty of Engineering, Yamaguchi University, Tokiwadai, Ube, Japan;2. Indian Statistical Institute (ISI), Chennai Centre, SETS (Society for Electronic Transactions and Security),MGR Knowledge City, CIT Campus, Taramani, Chennai 600 113, India;3. On leave from the Indian Institute ofTechnology Madras;4. Department of Mathematics, Indian Institute of Technology Kharagpur, West Bengal, India
Abstract:We study the class urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0001 of univalent analytic functions f in the unit disk urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0002 of the form urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0003 satisfying urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0004 where Ω will be a proper subdomain of urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0005 which is starlike with respect to urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0006. Let urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0007 be the unique conformal mapping of urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0008 onto Ω with urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0009 and urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0010 and urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0011. Let urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0012 denote the arclength of the image of the circle urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0013, urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0014. The first result in this paper is an inequality urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0015 for urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0016, which solves the general extremal problem urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0017, and contains many other well‐known results of the previous authors as special cases. Other results of this article cover another set of related problems about integral means in the general setting of the class urn:x-wiley:0025584X:media:mana201500027:mana201500027-math-0018.
Keywords:Univalent  close‐to‐convex  starlike and convex functions  integral means  arclength  symmetrization  subordination  30C45
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