# Videos

# Edward Witten

The Heidelberg Laureate Forum Foundation presents the HLF Portraits: Edward Witten

# Planetary Poles and Magnetic Fields

Dr Meghan Gray chats about magnetic fields and the Earth’s changeable poles.

# THAT Black Hole picture

Mike Merrifield, Omar Almaini and Meghan Gray react to the much-anticipated black hole photo from the Event Horizon Telescope Collaboration.

# Joe Polchinski Memorial Lecture: A Brief History of Branes

**Paul Townsend (University of Cambridge, Department of Applied Mathematics and Theoretical Physics, UK)**

Abstract of the memorial lecture “A Brief History of Branes”: Joe Polchinski made many groundbreaking discoveries in theoretical physics. This talk will focus on his contributions to the circle of ideas that led to M-theory in the late 1990s, especially his work of the 1980s on supermembranes (’86) and D-branes and T-duality (’89). This will be part of a survey of the changing role of branes in physics, with personal commentary on various related topics (such as M-branes, U-dualities, black branes) in supergravity and string theory.

Polchinski was a professor at the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara. His great contributions to theoretical physics, including the discovery of D-branes –– a type of membrane in string theory –– have led to advances in the understanding of string theory and quantum gravity. In 2008, he shared ICTP’s Dirac Medal with Juan Maldacena and Cumrun Vafa for their fundamental contributions to superstring theory. The three scientists’ profound achievements have helped to address outstanding questions like confinement of quarks and QCD mass spectrum from a new perspective and have found applications in practical calculations. In addition to the Dirac Medal, Polchinski was awarded the American Physical Society’s 2007 Dannie Heineman Prize for Mathematical Physics, the Milner Foundation’s Physics Frontiers Prize in 2013 and 2014, as well as the 2017 Breakthrough Prize in Fundamental Physics. His work touched the lives of many ICTP scientists, from the hundreds who attended his lectures to those who worked directly with him.