English

Pre-Schwarzian and Schwarzian norm estimates for certain classes of analytic and harmonic mappings

Complex Variables 2026-03-18 v1

Abstract

Let A\mathcal{A} denote the class of all analytic functions ff in the unit disk D:={zC:z<1}\mathbb{D}:=\{z\in\mathbb{C}: |z|<1\} such that f(0)=f(0)1=0f(0)=f'(0)-1=0. In this paper, we introduce a new subclass Cθ(γ)\mathcal{C}_\theta(\gamma) of A\mathcal{A} consisting of functions ff that satisfy the relation Re(eiθ(1+zf(z)f(z)))<(1+γ2)cosθ, zD, γ>0, and θ<π2, \textrm{Re}\left(e^{i\theta}\left(1+\frac{zf''(z)}{f'(z)}\right)\right)<\left(1+\frac{\gamma}{2}\right)\cos\theta,~ z\in\mathbb{D},~ \gamma>0, ~\text{and}~|\theta|<\frac{\pi}{2}, and investigate the Schwarzian derivative and Schwarzian norm for functions ff belonging to the class Cθ(γ)\mathcal{C}_\theta(\gamma). We establish sharp estimates for the Schwarzian norm Sf\|S_f\| of functions ff in the class Cθ(γ)\mathcal{C}_{\theta}(\gamma) and derive univalence criteria using both pre-Schwarzian and Schwarzian norm estimates. We also introduce a corresponding harmonic class HCθ(γ)\mathcal{HC}_{\theta}(\gamma) consisting of mappings f=h+gf = h+\overline{g} with hCθ(γ)h\in\mathcal{C}_{\theta}(\gamma) and dilatation ω=g/hAut(D)\omega=g'/h'\in\mathrm{Aut}(\mathbb{D}). For this harmonic class, we derive bounds for both the pre-Schwarzian and Schwarzian norms, including sharp results in special cases.

Keywords

Cite

@article{arxiv.2603.16388,
  title  = {Pre-Schwarzian and Schwarzian norm estimates for certain classes of analytic and harmonic mappings},
  author = {Vasudevarao Allu and Raju Biswas and Rajib Mandal},
  journal= {arXiv preprint arXiv:2603.16388},
  year   = {2026}
}

Comments

15 pages