On the essential spectrum of matrix operators

Estimates near the boundary for solutions of elliptic partial differential equations satisfying general boundary conditions. I

Shmuel Agmon, Avron Douglis, Louis Nirenberg · Communications on Pure and Applied Mathematics · 1959 · 3.8K citations

Natural Sciences, Mechanical Engineering, Differential Equations +10

Estimates near the boundary for solutions of elliptic partial differential equations satisfying general boundary conditions II

Shmuel Agmon, Avron Douglis, Louis Nirenberg · Communications on Pure and Applied Mathematics · 1964 · 1.3K citations

Natural Sciences, Mechanical Engineering, Differential Equations +11

The Essential Spectrum of Some Matrix Operators

F. V. Atkinson, Heinz Langer, R. Mennicken · Mathematische Nachrichten · 1994 · 205 citations

Natural Sciences, Chemistry, Algebra +12

The essential spectrum of elliptic systems of mixed order

Gerd Grubb, Giuseppe Geymonat · Mathematische Annalen · 1977 · 81 citations

Natural Sciences, Mathematics, Theoretical Physics +12

Critical layer singularities and complex eigenvalues in some differential equations of mathematical physics

John Adam · Physics Reports · 1986 · 62 citations

Natural Sciences, Mathematics, Physics +17