This page hosts information on Elias Pipping's talk "What is … a subgradient?" at the "What is …?" seminar. The talk will take place on Friday, June 7, 4:00pm at FU Arnimallee 6, SR 031.
The subgradient of a convex function can be seen as a generalisation of the gradient in that it does not require differentiability. After a brief introduction, I will say a word or two about its connection to nonsmooth constitutive laws and the Legendre transform.