Leonard Susskind (1 Jan 1940 - ) is one of the originators of the central idea of string theory, that photons, quarks, electrons, and neutrinos -- the supposedly elementary particles of the Standard Model -- are in fact different quantum excitations of a single extended 1-dimensional object. He has subsequently been a leading advocate of the view that the full range of vaccua of the string-theory landscape are realised, each corresponding to a distinct universe.
Susskind was the first to recast t’Hooft’s holographic principle as a principle in superstring theory. In this way he strengthened an argument, also lent support by Maldacina’s discovery of information-loss paradox. The title of his recent book The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics (2008) is a reference to the apparent threat to the universality of unitarity in quantum mechanics posed by Hawking radiation and the eventual disappearance of black holes. Violation of unitarity is also threatened by the measurement problem of quantum mechanics, and is viewed as necessary by those, like Penrose, who see the measurement problem as central to the problem of reconciling quantum theory with Einstein’s General Theory of Relativity.
Susskind was born in New York City, the son of a Jewish tradesman. He became a plumber at the age of 16. He subsequently enrolled in the City University of New York to study engineering. He obtained a PhD in theoretical physics from Cornell University in 1965, and held teaching positions at Yeshiva University and the University of Tel Aviv, before becoming Professor of Physics at Stanford University in 1979. There, among other teaching duties, he has taught the Stanford Continuing Studies courses about modern physics referred to as The Theoretical Minimum.