79 citations · 264 across the 22 of their papers we have counts for
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math.SP2013★ 8 cited
Triple Variational Principles for Self-Adjoint Operator Functions
Matthias Langer, Michael Strauss
For a very general class of unbounded self-adjoint operator function we prove upper bounds for eigenvalues which lie within arbitrary gaps of the essential spectrum. These upper bo…
math.SP2013
Essential spectrum of systems of singular differential equations
Orif O. Ibrogimov, Heinz Langer, Matthias Langer +1
In this paper we develop a new method to determine the essential spectrum of coupled systems of singular differential equations. Applications to problems from magnetohydrodynamics…