An Ingham--Müntz type theorem and simultaneous observation problems

International audienceWe establish a theorem combining the estimates of Ingham and Müntz – Szász. Moreover, we allow complex exponents instead of purely imaginary exponents for the Ingham type part or purely real exponents for the Müntz – Szász part. A very special case of this theorem allows us to prove the simultaneous observability of some string–heat and beam–heat systems.Nous établissons un théorème combinant les évaluations de type Ingham et Müntz – Szász