Biharmonic Green function of a ring domain

A biharmonic Green function of a circular ring domain $R=\{z\in \mathsf {C}: 0<r<|z|<1\}$ is found in the form 26741 \widehat{G}_{2}(z,\zeta)=|\zeta-z|^{2}G_{1}(z,\zeta)+\widehat{h}_{2}(z,\zeta), 26741 where $G_{1}(z,\zeta)$ is the harmonic Green function of the ring $R$, and $\widehat{h}_{2}(z,\zeta)$ is a specially constructed biharmonic function.

Riesz-Martin representation for positive super-polyharmonic functions in A Riemannian manifold

Letube a super-biharmonic function, that is,Δ2u≥0, on the unit discDin the complex plane, satisfying certain conditions. Then it has been shown thatuhas a representation analogous to the Poisson-Jensen representation for subharmonic functions onD. In the same vein, it is shown here that a functionuon any Green domainΩin a Riemannian manifold satisfying the conditions(−Δ)iu≥0for0≤i≤mhas a representation analogous to the Riesz-Martin representation for positive superharmonic functions onΩ.

Slow motion of viscous liquid in a semi-infinite channel

1. A slow two-dimensional steady motion of liquid caused by a pressure gradient in a semi-infinite channel is considered. The medium is bounded by two parallel semi-infinite planes represented in Fig. 1 by the straight lines AB, DE. The stream-function ψ is a biharmonic function of x, y which exactly satisfies the condition that AB, DE must be stream-lines, but the condition that there must be no velocity of slip on these boundaries is satisfied only approximately, and the calculated velocity of slip gives a measure of the accuracy of the solution.