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Ramakrishnan Vijayakumar

Publications and source records attributed to Ramakrishnan Vijayakumar.

8 recordsLinked to original sources
arXiv2026

Some sharp Schwarz type estimates and their applications in Banach spaces

The primary objective of this paper is to develop methodologies for investigating Schwarz type lemmas and to present their applications in Banach spaces. First, we improve upon the main results obtained by Osserman [Proc. Am. Math. Soc. 128: 3513-3517, 2000] and Chen et al. [J. Anal. Math. 152: 181-216, 2024]. Based on these sharp estimates, we then derive several sharp boundary Schwarz type lemmas (also known as Hopf type lemmas) for holomorphic mappings in Banach spaces, as well as for solutions to certain classes of elliptic partial differential equations on the Euclidean unit ball in $\mathbb{C}^n$ or on the unit disk in $\mathbb{C}$. Furthermore, we prove some sharp Schwarz type lemmas for holomorphic mappings that send a prescribed point to another prescribed point. Finally, these lemmas are applied to establish a sharp Minda type Schwarz inequality in Banach spaces and to provide a sharp refined bound on subballs of the unit ball.

math.CV↗
arXiv2022

Schwarz type lemmas and their applications in Banach spaces

The main purpose of this paper is to develop some methods to investigate the Schwarz type lemmas of holomorphic mappings and pluriharmonic mappings in Banach spaces. Initially, we extend the classical Schwarz lemmas of holomorphic mappings to Banach spaces, and then we apply these extensions to establish a sharp Bloch type theorem for pluriharmonic mappings on homogeneous unit balls of $\C^n$ and to obtain some sharp boundary Schwarz type lemmas for holomorphic mappings in Banach spaces. Furthermore, we improve and generalize the classical Schwarz lemmas of planar harmonic mappings into the sharp forms of Banach spaces, and present some applications to sharp boundary Schwarz type lemmas for pluriharmonic mappings in Banach spaces. Additionally, using a relatively simple method of proof, we prove some sharp Schwarz-Pick type estimates of pluriharmonic mappings in JB$^*$-triples, and the obtained results provide the improvements and generalizations of the corresponding results in \cite{CH20}.

math.CV↗
arXiv2021

Modifications of Bohr's inequality in various settings

The concept of Bohr radius for the class of bounded analytic functions was introduced by Harald Bohr in 1914. His initial result received greater interest and was sharpened-refined-generalized by several mathematicians in various settings--which is now called Bohr phenomenon. Various generalization of Bohr's classical theorem is now an active area of research and has been a source of investigation in numerous other function spaces and including holomorphic functions of several complex variables. Recently, a new generalization of Bohr's ideas was introduced and investigated by Kayumov et al.. In this note, we investigate and refine generalized Bohr's inequality for the class of quasi-subordinations.

math.CV↗
arXiv2021

Note on Weighted Bohr's Inequality

In this paper, first we give a new generalization of the Bohr's inequality for the class of bounded analytic functions $\mathcal{B'}$ and for the class of sense-preserving $K$-quasiconformal harmonic mappings of the form $f=h+\overline{g},$ where $h \in \mathcal{B'}.$ Finally we give a new generalization of the Bohr's inequality for the class of analytic functions subordinate to univalent functions and for the class of sense-preserving $K$-quasiconformal harmonic mappings of the form $f=h+\overline{g},$ where $h$ is subordinated to some analytic function.

math.CV↗
arXiv2021

Improved Bohr's phenomenon in quasi-subordination classes

Recently the present authors established refined versions of Bohr's inequality in the case of bounded analytic functions. In this article, we state and prove a generalization of these results in a reformulated "distance form" version and thereby we extend the refined versions of the Bohr inequality for the class of the quasi-subordinations which contains both the classes of majorization and subordination as special cases. As a consequence, we obtain several new results.

math.CV↗
arXiv2020

Refinement of the Classical Bohr Inequality

The classical inequality of Bohr asserts that if a power series converges in the unit disk and its sum has modulus less than or equal to $1$, then the sum of absolute values of its terms is less than or equal to $1$ for the subdisk $|z|<1/3$ and $1/3$ is the best possible constant. Recently, there has been a number of investigations on this topic. In this article, we present a refined version of Bohr's inequality along with few other related improved versions of previously known results.

math.CV↗