10 citations · 19 across the 14 of their papers we have counts for
14 papers
A Lewy theorem for harmonic quasiregular mappings in three-space
David Kalaj, Jian-Feng Zhu
Lewy's classical theorem asserts that a one-to-one planar harmonic mapping has nonvanishing Jacobian. We prove a three-dimensional bounded-distortion analogue: if \[ f:Ω\subset \ma…
Hilbert matrix norms on weighted Bergman spaces: even exponents and a counterexample to the beta formula
Hasi Wulan, Mengmeng Zhou, Jian-Feng Zhu
Let be the weighted Bergman space on the unit disk, where . For , consider the Hilbert matrix operator $\mathcal{H}f(z)=\sum…
Isoperimetric-type inequalities for pluriharmonic functions on the polydisc
Suman Das, Antti Rasila, Jian-Feng Zhu
We prove isoperimetric-type inequalities for complex-valued pluriharmonic functions in the unit polydisc . Denote by and $b^p_{…
The Nitsche--Hopf conjecture for minimal graphs
David Kalaj, Jian-Feng Zhu
We prove the Nitsche--Hopf conjecture for non-parametric minimal graphs over disks. If \(S\) is a minimal graph over a disk of radius \(R\), and if \(ξ\) is the point above the cen…
Improved Hölder regularity for elliptic equations of non-divergence type in the plane
Zhiqiang Hou, Jian-Feng Zhu
In this paper, we obtain an improved Hölder regularity for quasiregular gradient mappings which was studied by Baernstein and Kovalev.
Contraction properties for holomorphic functions via isoperimetric stability on the Bergman ball
David Kalaj, Jian-Feng Zhu
We prove a local contraction property for holomorphic functions that are nearly constant, relating weighted Bergman spaces $A^p_α(\B_n)$ and $A^q_β(\B_n)$. Our approach converts ge…