Differentiable perturbation of unbounded operators

Abstract

If $A(t)$ is a $C^{1,\al}$-curve of unbounded self-adjoint operators with compact resolvents and common domain of definition, then the eigenvalues can be parameterized $C^1$ in $t$. If $A$ is $C^{\infty }$ then the eigenvalues can be parameterized twice differentiable.

arXiv commentamstex 9 pages. Some misprints corrected