How violent are fast controls, III

For (coupled systems of) partial differential equations for which nullcontrol is possible in arbitrarily short time, the ‘standard’ blowup rate for the control cost is exponential in 1/T . It is shown how to derive this rate for a variety of systems, including the thermoelastic system with control restricted to a small patch in the domain and to a single component (thermal, displacement, or velocity). © 2007 Elsevier Inc. All rights reserved