English

Variability regions of close-to-convex functions

Complex Variables 2012-09-25 v2

Abstract

M. Biernacki gave concrete forms of the variability regions of z/f(z)z/f(z) and zf(z)/f(z)zf'(z)/f(z) of close-to-convex functions ff for a fixed zz with z<1|z|<1 in 1936. The forms are, however, not necessarily convenient to determine the shape of the full variability region of zf(z)/f(z)zf'(z)/f(z) over all close-to-convex functions ff and all points zz with z<1.|z|<1. We will propose a couple of other forms of the variability regions and see that the full variability region of zf(z)/f(z)zf'(z)/f(z) is indeed the complex plane minus the origin. We also apply them to study the variability regions of log[z/f(z)]\log[z/f(z)] and log[zf(z)/f(z)].\log[zf'(z)/f(z)].

Cite

@article{arxiv.1108.0461,
  title  = {Variability regions of close-to-convex functions},
  author = {Takao Kato and Toshiyuki Sugawa and Li-Mei Wang},
  journal= {arXiv preprint arXiv:1108.0461},
  year   = {2012}
}

Comments

12 pages

R2 v1 2026-06-21T18:45:07.790Z