Tea from 4:00 - 4:30 p.m. in Room 2-290
Refreshments afterwards, in Room 2-290

Abstract:
I will review several minimization problems where the solution is constrained
to remain above a certain "obstacle".
I will describe different applications that give rise to equations of second
order, fourth order and fractional powers of the Laplacian, and give some
ideas of how the optimal regularity of solutions is attained.