arXiv subjects

Vladimir Božin

Publications and source records attributed to Vladimir Božin.

4 recordsLinked to original sources

arXiv2026

Reverse Heinz type inequality, Mather beta function and coefficient estimates

In this paper, we prove that for two cyclically ordered sequences of complex numbers of unit modulus $(ξ_j)_{j=1}^{n}$ and $(ζ_j)_{j=1}^{n}$ the inequality: $$\bigg|\sum_{m=1}^{n}(ξ_{m+1}-ξ_m)ζ_m\bigg|^2+ \bigg|\sum_{m=1}^{n}(ξ_{m+1}-ξ_m)ζ_m^{-1}\bigg|^2\leqslant 4n^2\sin^2\fracπ{n}$$ holds for $n\geqslant 4$. As a consequence, for $n=4,$ we disprove Hall's conjecture on Heinz type inequality for harmonic self-mappings of the unit disk. The connection with the theory of elliptic billiards via the Mather beta function will also be given.

math.CV↗

arXiv2020

Sharp Riesz-Fejér inequality for harmonic Hardy spaces

We prove sharp version of Riesz-Fejér inequality for functions in harmonic Hardy space $h^p(\mathbb{D})$ on the unit disk $\mathbb{D}$, for $p>1,$ thus extending the result from \cite{KPK} and resolving the posed conjecture.

math.FA↗

arXiv2015

Bounds for Jacobian of harmonic injective mappings in n-dimensional space

Using normal family arguments, we show that the degree of the first nonzero homogenous polynomial in the expansion of $n$ dimensional Euclidean harmonic $K$-quasiconformal mapping around an internal point is odd, and that such a map from the unit ball onto a bounded convex domain, with $K< 3^{n-1}$, is co-Lipschitz. Also some generalizations of this result are given, as well as a generalization of Heinz's lemma for harmonic quasiconformal maps in $\mathbb R^n$ and related results.

math.AP↗

arXiv2011

Norm inequalities for vector functions

We study vector functions of ${\mathbb R}^n$ into itself, which are of the form $x \mapsto g(|x|)x\,,$ where $g : (0,\infty) \to (0,\infty) $ is a continuous function and call these radial functions. In the case when $g(t) = t^c$ for some $c \in {\mathbb R}\,,$ we find upper bounds for the distance of image points under such a radial function. Some of our results refine recent results of L. Maligranda and S. Dragomir. In particular, we study quasiconformal mappings of this simple type and obtain norm inequalities for such mappings.

math.CA↗