On the spectra of hypoelliptic operators in \({\mathbb{R}}^ 2\). (English) Zbl 0664.47035
Sufficient conditions are given for the spectra and essential spectra of certain classes of operators in \({\mathbb{R}}^ 2\) to be contained in an interval of the form [d,\(\infty)\).
MSC:
| 47F05 | General theory of partial differential operators |
| 47A10 | Spectrum, resolvent |
| 65H10 | Numerical computation of solutions to systems of equations |
| 35J05 | Laplace operator, Helmholtz equation (reduced wave equation), Poisson equation |
References:
| [1] | Birman M. S., Math. USSR-Sb 55 pp 125– (1961) |
| [2] | Muller-Pfeiffer E., Studio. Math. 24 pp 183– (1970) |
| [3] | DOI: 10.1002/mana.19730580121 · Zbl 0264.47014 · doi:10.1002/mana.19730580121 |
| [4] | DOI: 10.1112/S0025579300006203 · Zbl 0328.35067 · doi:10.1112/S0025579300006203 |
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