AUTHOR=Gadella Manuel , Lunardi José Tadeu , Manzoni Luiz A. TITLE=Editorial: Contact Interactions in Quantum Mechanics–Theory, Mathematical Aspects and Applications JOURNAL=Frontiers in Physics VOLUME=9 YEAR=2021 URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2021.645324 DOI=10.3389/fphy.2021.645324 ISSN=2296-424X