000K utf8 1500 ger 2050 urn:nbn:de:hbz:464-duett-05102006-1252250 3000 4000 About the regularity theory for elliptic systems and harmonic mappings 4000 Zur Regularitätstheorie elliptischer Systeme und harmonischer Abbildungen 4209 This thesis deals with regualrity questions of elliptic and parabolic systems of partial differential equations of second order. With the help of a Harnack inequality it is shown that bounded weak solutions of certain parabolic systems are Hölder continous. In the second chapter we prove regularity theorems for weak harmonic mappings in the interior and at the boundary, an important tool for these theorems are again two Harnack inequalities. The last two chapters deal with degenerate elliptic systems, for certain degenerate elliptic coefficients (e.g. in the Muckenhouptclass A2) we prove two Harnack inequalities and show with these inequalities some regularity theorems for degenerate elliptic systems. 4950 https://nbn-resolving.org/urn:nbn:de:hbz:464-duett-05102006-1252250$xR$3Volltext$534 4961 https://duepublico2.uni-due.de/receive/duepublico_mods_00005701 5010 51 5051 510 5550 a-priori estimates 5550 degenerate elliptic systems 5550 harmonic mappings 5550 Harnack inequality 5550 Muckenhoupt classes 5550 parabolic systems