Leonard Susskind (; born 1940) is an American
physicist, who is professor of theoretical
physics at Stanford University, and founding
director of the Stanford Institute for Theoretical
Physics. His research interests include string
theory, quantum field theory, quantum statistical
mechanics and quantum cosmology. He is a member
of the National Academy of Sciences of the
US, and the American Academy of Arts and Sciences,
an associate member of the faculty of Canada's
Perimeter Institute for Theoretical Physics,
and a distinguished professor of the Korea
Institute for Advanced Study.Susskind is widely
regarded as one of the fathers of string theory.
He was the first to give a precise string-theory
interpretation of the holographic principle
in 1995 and the first to introduce the idea
of the string theory landscape in 2003.Susskind
was awarded the 1998 J. J. Sakurai Prize,
and the 2018 Oskar Klein Medal.
== Early life and education ==
Leonard Susskind was born to a Jewish family
from the South Bronx section of New York City.
He began working as a plumber at the age of
16, taking over from his father who had become
ill. Later, he enrolled in the City College
of New York as an engineering student, graduating
with a B.S. in physics in 1962. In an interview
in the Los Angeles Times, Susskind recalls
the moment he discussed with his father this
change in career path: "When I told my father
I wanted to be a physicist, he said: ‘Hell
no, you ain’t going to work in a drug store’.
I said, "No, not a pharmacist." I said, ‘Like
Einstein.’ He poked me in the chest with
a piece of plumbing pipe. ‘You ain’t going
to be no engineer’, he said. ‘You’re
going to be Einstein.’" Susskind then studied
at Cornell University under Peter A. Carruthers
where he earned his Ph.D. in 1965.
== Career ==
Susskind was an assistant professor of physics,
then an associate professor at Yeshiva University
(1966–1970), after which he went for a year
to the Tel Aviv University (1971–72), returning
to Yeshiva to become a professor of physics
(1970–1979). Since 1979 he has been professor
of physics at Stanford University, and since
2000 has held the Felix Bloch professorship
of physics.
Susskind was awarded the 1998 J. J. Sakurai
Prize for his "pioneering contributions to
hadronic string models, lattice gauge theories,
quantum chromodynamics, and dynamical symmetry
breaking". Susskind's hallmark, according
to colleagues, has been the application of
"brilliant imagination and originality to
the theoretical study of the nature of the
elementary particles and forces that make
up the physical world".In 2007, Susskind joined
the faculty of Perimeter Institute for Theoretical
Physics in Waterloo, Ontario, Canada, as an
associate member. He has been elected to the
National Academy of Sciences and the American
Academy of Arts and Sciences. He is also a
distinguished professor at Korea Institute
for Advanced Study.
=== Scientific career ===
Susskind was one of at least three physicists,
alongside Yoichiro Nambu and Holger Bech Nielsen,
who independently discovered during or around
1970 that the Veneziano dual resonance model
of strong interactions could be described
by a quantum mechanical model of oscillating
strings, and was the first to propose the
idea of the string theory landscape. Susskind
has also made important contributions in the
following areas of physics:
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 (Andrei Sakharov's work was first,
but was mostly unknown in the Western hemisphere)
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 (FRW/CFT duality)
Most recently, application of ideas from information
and computation theory, such as quantum complexity,
to the physics and thermodynamics of black
holes, and holographic theories in general.
== Books ==
Susskind is the author of several popular
science books.
=== The Cosmic Landscape ===
The Cosmic Landscape: String Theory and the
Illusion of Intelligent Design is Susskind's
first popular science book, published by Little,
Brown and Company on December 12, 2005. It
is Susskind's attempt to bring his idea of
the anthropic landscape of string theory to
the general public. In the book, Susskind
describes how the string theory landscape
was an almost inevitable consequence of several
factors, one of which was Steven Weinberg's
prediction of the cosmological constant in
1987. The question addressed here is why our
universe is fine-tuned for our existence.
Susskind explains that Weinberg calculated
that if the cosmological constant was just
a little different, our universe would cease
to exist.
=== The Black Hole War ===
The Black Hole War: My Battle with Stephen
Hawking to Make the World Safe for Quantum
Mechanics is Susskind's second popular science
book, published by Little, Brown, and Company
on July 7, 2008. The book is his most famous
work and explains what he thinks would happen
to the information and matter stored in a
black hole when it evaporates. The book sparked
from a debate that started in 1981, when there
was a meeting of physicists to try to decode
some of the mysteries about how particles
of particular elemental compounds function.
During this discussion Stephen Hawking stated
that the information inside a black hole is
lost forever as the black hole evaporates.
It took 28 years for Leonard Susskind to formulate
his theory that would prove Hawking wrong.
He then published his theory in his book,
The Black Hole War. Like The Cosmic Landscape,
The Black Hole War is aimed at the lay reader.
He writes: "The real tools for understanding
the quantum universe are abstract mathematics:
infinite dimensional Hilbert spaces, projection
operators, unitary matrices and a lot of other
advanced principles that take a few years
to learn. But let's see how we do in just
a few pages".
=== The Theoretical Minimum book series ===
Susskind co-authored a series of companion
books to his lecture series The Theoretical
Minimum. The first of these, The Theoretical
Minimum: What You Need to Know to Start Doing
Physics, was published in 2013 and presents
the modern formulations of classical mechanics.
The second of these, Quantum Mechanics: The
Theoretical Minimum, was published in February
2014. The third book, Special Relativity and
Classical Field Theory: The Theoretical Minimum
(September 26, 2017), introduces readers to
Einstein's special relativity and Maxwell's
classical field theory.
== The Theoretical Minimum lecture series
==
Susskind teaches a series of Stanford Continuing
Studies courses about modern physics referred
to as The Theoretical Minimum. The title of
the series is a clear reference to the Landau's
famous comprehensive exam called the "Theoretical
Minimum" which students were expected to pass
before admission to his school. The Theoretical
Minimum lectures later formed the basis for
the books of the same name. The goal of the
courses is to teach the basic but rigorous
theoretical foundations required to study
certain areas of physics. The sequence covers
classical mechanics, relativity, quantum mechanics,
statistical mechanics, and cosmology, including
the physics of black holes.These courses are
available on The Theoretical Minimum website,
on iTunes, and on YouTube. The courses are
intended for the mathematically literate public
as well as physical science/mathematics students.
Susskind aims the courses at people with prior
exposure to algebra, calculus, vectors, differential
calculus, integrals, and perhaps differential
operators, matrices, and linear equations.
Homework and study outside of class is otherwise
unnecessary. Susskind explains most of the
mathematics used, which form the basis of
the lectures.
== Cornell Messenger Lectures ==
Susskind gave 3 lectures "The Birth of the
Universe and the Origin of Laws of Physics"
April 28-May 1, 2014 in the Cornell Messenger
Lecture series which are posted on a Cornell
website.
== Smolin–Susskind debate ==
The Smolin–Susskind debate refers to the
series of intense postings in 2004 between
Lee Smolin and Susskind, concerning Smolin’s
argument that the "anthropic principle cannot
yield any falsifiable predictions, and therefore
cannot be a part of science." It began on
July 26, 2004, with Smolin's publication of
"Scientific alternatives to the anthropic
principle". Smolin e-mailed Susskind asking
for a comment. Having not had the chance to
read the paper, Susskind requested a summarization
of his arguments. Smolin obliged, and on July
28, 2004, Susskind responded, saying that
the logic Smolin followed "can lead to ridiculous
conclusions". The next day, 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." This
was followed by another paper by Susskind
which made a few comments about Smolin's theory
of "cosmic natural selection". The Smolin-Susskind
debate finally ended with each of them agreeing
to write a final letter which would be posted
on the edge.org website, with three conditions
attached: (1) No more than one letter each;
(2) Neither sees the other's letter in advance;
(3) No changes after the fact.
== Personal life ==
He has been married twice, first in 1960,
and has four children. Susskind is a great-grandfather.
== 
See also ==
Supersymmetry
List of theoretical physicists
