Abstract and Applied Analysis
Volume 6 (2001), Issue 8, Pages 441-488

Factor spaces and implications on Kirchhoff equations with clamped boundary conditions

Irena Lasiecka and Roberto Triggiani

Department of Mathematics, University of Virginia, Charlottesville 22904, VA, USA

Received 18 June 2001

Copyright © 2001 Irena Lasiecka and Roberto Triggiani. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We consider mixed problems for the Kirchhoff elastic and thermoelastic systems, subject to boundary control in the clamped boundary conditions BC (clamped control). If w denotes the elastic displacement and θ the temperature, we establish sharp regularity of {w,wt,wtt} in the elastic case, and of {w,wt,wtt,θ} in the thermoelastic case. Our results complement those by Lagnese and Lions (1988), where sharp (optimal) trace regularity results are obtained for the corresponding boundary homogeneous cases. The passage from the boundary homogeneous cases to the corresponding mixed problems involves a duality argument. However, in the present case of clamped BC, and only in this case, the duality argument in question is both delicate and technical. In this respect, the clamped BC are “exceptional” within the set of canonical BC (hinged, clamped, free BC). Indeed, it produces new phenomena which are accounted for by introducing new, untraditional factor (quotient) spaces. These are critical in describing both interior regularity and exact controllability of mixed elastic and thermoelastic Kirchhoff problems with clamped controls.