English

On Convex Dominants of Exact Differential Subordination

Complex Variables 2020-11-24 v1

Abstract

Let hh be a non vanishing convex univalent function and pp be an analytic function in D\mathbb{D}. We consider the differential subordination ψi(p(z),zp(z))h(z)\psi_i(p(z), z p'(z)) \prec h(z) with the admissible functions in consideration as ψ1:=(βp(z)+γ)α((βp(z)+γ)β(1α)+zp(z))\psi_1:=(\beta p(z)+\gamma)^{-\alpha}\left(\tfrac{(\beta p(z)+\gamma)}{\beta(1-\alpha)}+ z p'(z)\right) and ψ2:=1γβarctan(βγp1α(z))+(1αβp2(1α)(z)+γ)zp(z)pα(z)\psi_2:=\tfrac{1}{\sqrt{\gamma \beta}}\arctan\left(\sqrt{\tfrac{\beta}{\gamma}}p^{1-\alpha}(z)\right)+\left(\tfrac{1-\alpha}{\beta p^{2 (1-\alpha)}(z)+\gamma}\right)\tfrac{z p'(z)}{p^{\alpha}(z)}. The objective of this paper is to find the dominants, preferably the best dominant(say qq) of the solution of the above differential subordination satisfying ψi(q,nzq(z))=h(z)\psi_i(q, n zq'(z))= h(z). Further, we show that ψi(q,zq(z))=h(z)\psi_i(q,zq'(z))= h(z) is an exact differential equation and qq is a convex univalent function in D\mathbb{D}. In addition, we estimate the sharp lower bound of \REp\RE p for different choices of hh and derive a univalence criteria for functions in H\mathcal{H}(class of analytic normalized functions) as an application to our results.

Keywords

Cite

@article{arxiv.2011.11404,
  title  = {On Convex Dominants of Exact Differential Subordination},
  author = {S. Sivaprasad Kumar and Shagun Banga},
  journal= {arXiv preprint arXiv:2011.11404},
  year   = {2020}
}