Ga. Afrouzi et Kj. Brown, On principal eigenvalues for boundary value problems with indefinite weight and Robin boundary conditions, P AM MATH S, 127(1), 1999, pp. 125-130
We investigate the existence of principal eigenvalues (i.e., eigenvalues co
rresponding to positive eigenfunctions) for the boundary value problem -Del
ta u(x) = lambda g(x)u(x) on D; partial derivative u/partial derivative u(x
) + alpha u(x) = 0 on partial derivative D, where D is a bounded region in
R-N, g is an indefinite weight function and alpha is an element of R may be
positive, negative or zero.