Leonard Susskind

Scientific Contributions

• The independent discovery of the string theory model of particle physics
• The theory of quark confinement
• The development of Hamiltonian lattice gauge theory known as Kogut-Susskind fermions
• The theory of scaling violations in deep inelastic electroproduction
• The theory of symmetry breaking sometimes known as "technicolor theory"
• The second, yet independent, theory of cosmological baryogenesis
• String theory of black hole entropy
• The principle of black hole complementarity
• The causal patch hypothesis
• The holographic principle
• M-theory, including development of the BFSS matrix model
• Introduction of holographic entropy bounds in physical cosmology
• The idea of an anthropic string theory landscape
• The Census Taker's Hat

Black Hole Complementarity

• Stephen Hawking - information is lost in an evaporating black hole once it passes through the event horizon and is inevitably destroyed at the singularity
• Can turn pure quantum states into mixed states, some physicists have wondered if a complete theory of quantum gravity might be able to conserve information with a unitary time evolution.
• How can this be possible if information cannot escape the event horizon without traveling faster than light?
• Ruled out Hawking radiation as the carrier of the missing information
• It also appears as if information cannot be "reflected" at the event horizon as there is nothing special about it locally
• Leonard Susskind proposed a radical resolution - information is both reflected at the event horizon and passes through the event horizon and cannot escape, with the catch being no observer can confirm both stories simultaneously
• This isn't to say there are two copies of the information lying about — one at or just outside the horizon, and the other inside the black hole — as that would violate the no cloning theorem
• Instead, an observer can only detect the information at the horizon itself, or inside, but never both simultaneously
• Complementarity is a feature of the quantum mechanics of noncommuting observables, and Susskind proposed that both stories are complementary in the quantum sense

String Theory

Awards

• Pomeranchuk Prize (2008)
• American Institute of Physics' Science Writing Award
• Sakurai Prize (1998)
• Boris Pregel Award
• New York Academy of Sciences (1975)

Career

• "Solution" to unified field theory issue
• Treats point particles as strings, one dimensional objects
• Describes how these strings propagate through space and interact with each other
• One of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries gravitational force
• Theory of quantum gravity
• One of the leading theories, no real way to confirm or deny

• Started as an assistant professor of physics at various universities
• Has been professor of physics at Stanford University since 1979,
• 1998 J. J. Sakurai Prize for his "pioneering contributions to hadronic string models, lattice gauge theories, quantum chromodynamics, and dynamical symmetry breaking".
• Elected to the National Academy of Sciences and the American Academy of Arts and Sciences
• Professor at Korea Institute for Advanced Study

Fame

• Well known in academia and physics research community
• Not as famous as he should be, relatively quiet personality
• Thinker > Talker

Publications

• The Cosmic Landscape
• brings String theory to public eye
• The Black Hole War
• explains his efforts to resolve the information theory paradox on evaporating black holes
• The Theoretical Minimum book series
• More education based texts
• Lecture series
• Black Hole Complementarity and the Harlow-Hayden Conjecture
• New Concepts for Old Black Holes

Early Life

Leonard Susskind

• Grew up in the South Bronx of NYC
• Now lives in Palo Alto, California.
• First worked as a plumber
• Attended City College of New York as an engineering student
• Graduating with a B.S. in physics in 1962
• Studied at Cornell University under Peter A. Carruthers where he earned his Ph.D. in 1965.
• Married twice, first in 1960, and has four children.

• Born in 1940
• Professor of theoretical physics at Stanford University,
• Director of the Stanford Institute for Theoretical Physics
• "Father" of String Theory

Smolin–Susskind Debate

• close with Richard Feynman
• great-grandfather

• Lee Smolin attacks Susskind's "anthropic principle" saying that it cannot yield any falsifiable predictions, and therefore cannot be a part of science
• Susskind responded, saying that the logic Smolin followed "can lead to ridiculous conclusions"
• Smolin responded, saying that "If a large body of our colleagues feels comfortable believing a theory that cannot be proved wrong, then the progress of science could get stuck, leading to a situation in which false, but unfalsifiable theories dominate the attention of our field."
• Susskind comments on Smolin's theory of Cosmic Natural Selection
• Ended debate with a final letter

Bibliography

Leonard Susskind

• http://theoreticalminimum.com/biography
• https://physics.stanford.edu/people/faculty/leonard-susskind
• https://www.ted.com/talks/leonard_susskind_my_friend_richard_feynman
• http://www.telegraph.co.uk/culture/books/10654762/The-man-who-proved-Stephen-Hawking-wrong.html

American Physicist