Daniel Z. Freedman

Stanford University


Primary Section: 13, Physics
Membership Type: Member (elected 2021)

Biosketch

Daniel Freedman is a theoretical physicist whose research specialties include supersymmetric quantum field theories and supergravity. In 1974 he pointed out that, due to the newly discovered weak neutral current, notoriously weak neutrino interactions are enhanced in the scattering of neutrinos incident upon a heavy atomic nucleus. This effect, called coherent neutrino-nucleus scattering, was first confirmed experimentally in 2017. In supersymmetric field theories, particles with integer spin, called bosons, are linked together by a symmetry with particles of 1/2-integer spin, called  fermions. In 1976, Freedman (together with Peter Van Nieuwenhuizen and Sergio Ferrara) discovered supergravity, the first theory in which the graviton, a boson of spin 2, is  unified with  a  hypothetical  particle,  the gravitino  with  spin  3/2. The gravitino and other predictions of supersymmetry have not yet been confirmed by experiment, but their intricate and unifying theoretical features have been very influential. Freedman received his Ph.D. degree in 1964 at the University of Wisconsin. After postdoctoral appointments at Imperial College, London, University of California, Berkeley, and the Institute for Advanced Study, Princeton, he joined the physics faculty at the State University of New York, Stony Brook, and moved to the Massachusetts Institute of Technology in 1980. Since retirement there in 2016, he has been a visiting professor at Stanford University. He has been awarded the Dirac Medal and Prize, the Dannie Heineman Prize, the Majorana Medal, and the Special Breakthrough Prize in Fundamental Physics.

Research Interests

The AdS/CFT Correspondence (written in full as anti-de Sitter conformal field theory) was first proposed in late  1997  by  Juan  Maldacena. The AdS spacetime has a (d + 1) dimensional infinite ”bulk” geometry with a  d-dimensional  ”boundary” at large spatial distance.  One must specify boundary conditions to obtain unique solutions of field equations in AdS. There are solutions of 10-dimensional superstring theory whose geometry is the ”product” of 5-dimensional AdS and a 5-dimensional sphere.  Maldacena argued convincingly for a ”holographic” correspondence between features of solutions of gravitational field equations in the bulk and features of a non-gravitational field theory on the boundary. Thus information on bulk quantum gravity in d + 1 dimensions is encoded by a quantum theory  wIthout  gravity in d-dimensions. The converse is also important.  Classical solutions of the bulk Einstein equations are relatively easy to obtain. They give information on the quantum dynamics of the boundary theory, with one dimension less, and most of this information cannot be obtained by traditional methods of quantum field theory.  Much of Freedman’s  research in the past 24 years  involves AdS/CFT. His early papers contained new methods to perform calculations in the bulk and applied them to obtain precise evidence that the bulk-boundary correspondence is correct. More recent papers show how to use bulk supergravity theories to calculate the free energy of the boundary supersymmetric theory, which is a fundamental observable quantity.

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