The Black Hole Information Paradox
Physics insists information can never be destroyed. Black holes appear to destroy it. Both of those cannot be true.
1974/75 (Hawking radiation), 1976 (the paradox stated)24 min read
Argentine-American theoretical physics
Juan Maldacena
1968
Argentine physicist at the Institute for Advanced Study whose 1997 conjecture relating string theory in anti-de Sitter space to a conformal field theory on its boundary (AdS/CFT) is the most-cited result in modern theoretical physics. It supplies the sharpest existing argument that black hole evaporation is unitary, because the boundary theory is manifestly so.