Carl Bender is an applied mathematician and mathematical physicist holding positions at Washington University in St. Louis, the University of Heidelberg, Imperial College, London. He was also one of my own favorite lecturers. He taught me about perturbation theory and asymptotic series which are powerful mathematical tools for solving difficult problems in physics. I invited Carl on to the podcast to discuss complex numbers, and their application in physics. At a conceptual level Carl talks about the link between mathematics and reality, the history of complex numbers and what they are good for, his research into weird new quantum systems known as PT-symmetric quantum systems, his interactions with Richard Feynman, and the role that beauty plays in Mathematical discovery. ►Watch on YouTube:https://youtu.be/UbHaAziq6jY ►You can find out more about Carl Here:https://web.physics.wustl.edu/cmb/ These conversations are supported by the Andrea von Braun foundation (http://www.avbstiftung.de/), as an exploration of the rich, exciting, connected, scientifically literate, and (most importantly) sustainable future of humanity. The views expressed in these episodes are my own and those of my guests.