Dispersion Relations Alone Cannot Guarantee Causality L. Gavassino,1M. Disconzi,1and J. Noronha2 1Department of Mathematics, Vanderbilt University, 1326 Stevenson Center Lane, Nashville, Tennessee 37240, USA 2Illinois Center for Advanced Studies of the Universe & Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3003, USA (Received 2 August 2023; accepted 29 March 2024; published 17 April 2024) We show that linear superpositions of plane waves involving a ...