10 citations · 19 across the 14 of their papers we have counts for
5 papers · 2 filters
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…
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…