Nathan "Nati" Seiberg (/ˈsaɪbɜːrɡ/; born September 22, 1956) is an Israeli American theoretical physicist who works on quantum field theory and string theory. He is currently a professor at the Institute for Advanced Study in Princeton, New Jersey, United States.

He was recipient of a 1996 MacArthur Fellowship^[1] and the Dannie Heineman Prize for Mathematical Physics in 1998.^[2] In July 2012, he was an inaugural awardee of the Breakthrough Prize in Fundamental Physics, the creation of physicist and internet entrepreneur, Yuri Milner.^[3] In 2016, he was awarded the Dirac Medal of the ICTP. He is a Fellow of the American Academy of Arts and Sciences and a Member of the US National Academy of Sciences.

His contributions include:

• Ian Affleck, Michael Dine, and Seiberg explored nonperturbative effects in supersymmetric field theories.^[4] This work demonstrated, for the first time, that nonperturbative effects in four-dimensional field theories do not respect the supersymmetry nonrenormalization theorems. This understanding led them to find four-dimensional models with dynamical supersymmetry breaking.
• In a series of papers, Michael Dine and Seiberg explored various aspects of string theory. In particular, Dine, Ryan Rohm, Seiberg, and Edward Witten proposed a supersymmetry breaking mechanism based on gluino condensation,^[5] Dine, Seiberg, and Witten showed that terms similar to Fayet–Iliopoulos D-terms arise in string theory,^[6] and Dine, Seiberg, X. G. Wen, and Witten studied instantons on the string worldsheet.^[7]
• Gregory Moore and Seiberg studied Rational Conformal Field Theories. In the course of doing it, they invented modular tensor categories and described many of their properties.^[8] They also explored the relation between Witten’s Topological Chern–Simons theory and the corresponding Rational Conformal Field Theory.^[9] This body of work was later used in mathematics and in the study of topological phases of matter.
• In the 90’s, Seiberg realized the significance of holomorphy as the underlying reason for the perturbative supersymmetry nonrenormalization theorems^[10] and initiated a program to use it to find exact results in complicated field theories including several N=1 supersymmetric gauge theories in four dimension. These theories exhibit unexpected rich phenomena like confinement with and without chiral symmetry breaking and a new kind of electric-magnetic duality – Seiberg duality.^[11] Kenneth Intriligator and Seiberg studied many more models and summarized the subject in lecture notes.^[12] Later, Intriligator, Seiberg and David Shih used this understanding of the dynamics to present four-dimensional models with dynamical supersymmetry breaking in a metastable vacuum.^[13]
• Seiberg and Witten studied the dynamics of four-dimensional N=2 supersymmetric theories – Seiberg–Witten theory. They found exact expressions for several quantities of interest. These shed new light on interesting phenomena like confinement, chiral symmetry breaking, and electric-magnetic duality.^[14] This insight was used by Witten to derive the Seiberg–Witten invariants. Later, Seiberg and Witten extended their work to the four-dimensional N=2 theory compactified to three dimensions.^[15]
• Intriligator and Seiberg found a new kind of duality in three-dimensional N=4 supersymmetric theories, which is reminiscent of the well-known 2D mirror symmetry – 3D mirror symmetry.^[16]
• In a series of papers with various collaborators, Seiberg studied many supersymmetric theories in three, four, five, and six dimensions. The three-dimensional N=2 supersymmetric theories^[17] and their dualities were shown to be related to the four-dimensional N=1 theories.^[18] And surprising five-dimensional theories with N=2 supersymmetries were discovered^[19] and analyzed.^[20]
• As part of his work on the BFSS matrix model, Seiberg discovered little string theories.^[21] These are limits of string theory without gravity that are not local quantum field theories.
• Seiberg and Witten identified a particular low-energy limit (Seiberg–Witten limit) of theories containing open strings in which the dynamics becomes that of noncommutative quantum field theory – a field theory on a non-commutative geometry. They also presented a map (Seiberg–Witten map) between standard gauge theories and gauge theories on a noncommutative space.^[22] Shiraz Minwalla, Mark Van Raamsdonk and Seiberg uncovered a surprising mixing between short-distance and long-distance phenomena in these field theories on a noncommutative space. Such mixing violates the standard picture of the renormalization group. They referred to this phenomenon as UV/IR mixing.^[23]
• Davide Gaiotto, Anton Kapustin, Seiberg, and Brian Willett introduced the notion of higher-form global symmetries and studied some of their properties and applications.^[24]

• Gauge theory
• Instanton
• String theory
• Two-dimensional conformal field theory
• S-duality
• Noncommutative quantum field theory
• Anomaly (physics)