Propagation of polarization sets for systems of generalized transverse type and for systems of MHD type
by Rayhana Darwich
Date of Examination:2023-05-02
Date of issue:2023-06-16
Advisor:Prof. Dr. Ingo Witt
Referee:Prof. Dr. Dorothea Bahns
Referee:Dr. Christian Jaeh
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Description:PhD Thesis
Abstract
English
Polarization sets were introduced by Dencker (1982) as a refinement of wavefront sets to the vector-valued case. He also clarified the propagation of polarization sets when the characteristic variety of the pseudodifferential system under study consists of two hypersurfaces intersecting tangentially (1992), or transversally (1995). In this thesis, we consider the case of more than two intersecting characteristic hypersurfaces that are interesting transversally (and we give a note on the tangential case). Mainly, we consider two types of systems which we name "systems of generalized transverse type" and "systems of MHD type", and we show that we can get a result for the propagation of polarization set similar to Dencker's result for systems of transverse type. Furthermore, we give an application to the MHD equations.
Keywords: Polarization sets; wavefront sets; systems of transverse type; systems of uniaxial type; systems of generalized transverse type; systems of MHD type; magnetohydrodynamics; ideal MHD equations; pseudodifferential operators; systems of real principal type; propagation of polarization sets; microlocal analysis