A new boundary observability inequality for the Maxwell equations and the elastodynamic system is obtained. We use modified multipliers to obtain such an inequality as long as a geometric condition on the region holds and important parameters of the model are (numerically) related. This allow us to use the HUM to conclude a "simultaneous'' boundary exact controllability result.
"Simultaneous exact controllability: an elastodynamic system and Maxwell's equations." Adv. Differential Equations 16 (5/6) 551 - 571, May/June 2011.