Edward Witten

Edward Witten (born August 26, 1951) is an American mathematical and theoretical physicist.

He is a professor emeritus in the school of natural sciences at the Institute for Advanced Study in Princeton.

Witten is a researcher in string theory, quantum gravity, supersymmetric quantum field theories, and other areas of mathematical physics.

Witten's work has also significantly impacted pure mathematics.

Witten was born on August 26, 1951, in Baltimore, Maryland, to a Jewish family.

He is the son of Lorraine (née Wollach) Witten and Louis Witten, a theoretical physicist specializing in gravitation and general relativity.

He had aspirations in journalism and politics and published articles in both The New Republic and The Nation in the late 1960s.

Witten attended the Park School of Baltimore (class of '68), and received his Bachelor of Arts degree with a major in history and minor in linguistics from Brandeis University in 1971.

In 1972 he worked for six months on George McGovern's presidential campaign.

Witten attended the University of Michigan for one semester as an economics graduate student before dropping out.

He returned to academia, enrolling in applied mathematics at Princeton University in 1973, then shifting departments and receiving a PhD in physics in 1976 and completing a dissertation, "Some problems in the short distance analysis of gauge theories", under the supervision of David Gross.

He held a fellowship at Harvard University (1976–77), visited Oxford University (1977–78), was a junior fellow in the Harvard Society of Fellows (1977–1980), and held a MacArthur Foundation fellowship (1982).

In the late 1980s, Witten coined the term topological quantum field theory for a certain type of physical theory in which the expectation values of observable quantities encode information about the topology of spacetime.

In particular, Witten realized that a physical theory now called Chern–Simons theory could provide a framework for understanding the mathematical theory of knots and 3-manifolds.

Although Witten's work was based on the mathematically ill-defined notion of a Feynman path integral and therefore not mathematically rigorous, mathematicians were able to systematically develop Witten's ideas, leading to the theory of Reshetikhin–Turaev invariants.

Another result for which Witten was awarded the Fields Medal was his proof in 1981 of the positive energy theorem in general relativity.

This theorem asserts that (under appropriate assumptions) the total energy of a gravitating system is always positive and can be zero only if the geometry of spacetime is that of flat Minkowski space.

It establishes Minkowski space as a stable ground state of the gravitational field.

While the original proof of this result due to Richard Schoen and Shing-Tung Yau used variational methods, Witten's proof used ideas from supergravity theory to simplify the argument.

A third area mentioned in Atiyah's address is Witten's work relating supersymmetry and Morse theory, a branch of mathematics that studies the topology of manifolds using the concept of a differentiable function.

Witten's work gave a physical proof of a classical result, the Morse inequalities, by interpreting the theory in terms of supersymmetric quantum mechanics.

In 1990, he became the first physicist to be awarded a Fields Medal by the International Mathematical Union, for his mathematical insights in physics, such as his 1981 proof of the positive energy theorem in general relativity, and his interpretation of the Jones invariants of knots as Feynman integrals.

He is considered the practical founder of M-theory.

Witten was awarded the Fields Medal by the International Mathematical Union in 1990.

In a written address to the ICM, Michael Atiyah said of Witten:

"Although he is definitely a physicist (as his list of publications clearly shows) his command of mathematics is rivaled by few mathematicians, and his ability to interpret physical ideas in mathematical form is quite unique. Time and again he has surprised the mathematical community by a brilliant application of physical insight leading to new and deep mathematical theorems ... He has made a profound impact on contemporary mathematics. In his hands physics is once again providing a rich source of inspiration and insight in mathematics."

As an example of Witten's work in pure mathematics, Atiyah cites his application of techniques from quantum field theory to the mathematical subject of low-dimensional topology.

By the mid 1990s, physicists working on string theory had developed five different consistent versions of the theory.

These versions are known as type I, type IIA, type IIB, and the two flavors of heterotic string theory (SO(32) and E8×E8).

The thinking was that of these five candidate theories, only one was the actual correct theory of everything, and that theory was the one whose low-energy limit matched the physics observed in our world today.

Speaking at the string theory conference at University of Southern California in 1995, Witten made the surprising suggestion that these five string theories were in fact not distinct theories, but different limits of a single theory, which he called M-theory.

Witten's proposal was based on the observation that the five string theories can be mapped to one another by certain rules called dualities and are identified by these dualities.

It led to a flurry of work now known as the second superstring revolution.

Another of Witten's contributions to physics was to the result of gauge/gravity duality.

In 1997, Juan Maldacena formulated a result known as the AdS/CFT correspondence, which establishes a relationship between certain quantum field theories and theories of quantum gravity.

Maldacena's discovery has dominated high-energy theoretical physics for the past 15 years because of its applications to theoretical problems in quantum gravity and quantum field theory.

Witten's foundational work following Maldacena's result has shed light on this relationship.

In collaboration with Nathan Seiberg, Witten established several powerful results in quantum field theories.

In their paper on string theory and noncommutative geometry, Seiberg and Witten studied certain noncommutative quantum field theories that arise as limits of string theory.

In another well-known paper, they studied aspects of supersymmetric gauge theory.