An oscillatory bifurcation from infinity, and from zero

The problem (where B is a unit ball in Rn) \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Delta u +\lambda (u + ug(u)) = 0,\, x \in B,\, u = 0 {\rm for} x \in \partial B $$\end{document}, with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$lim_{u \rightarrow \infty} g(u) = 0$$\end{document}, is known to have a curve of positive solutions bifurcating from infinity at λ = λ1, the principal eigenvalue. It turns out that a similar situation may occur, when g(u) is oscillatory for large u, instead of being small. In case n = 1, we can also prove existence of infinitely many solutions at λ = λ1 on this curve. Similarly, we consider oscillatory bifurcation from zero.