Dirac Medal Honors Work in Turbulence

To mark the occasion of P.A.M. Dirac’s birthday on 8 August, the Abdus Salam International Centre for Theoretical Physics in Trieste, Italy, awards the Dirac Medal annually on that date to recognize contributions to theoretical physics and mathematics. This year, the ICTP honored Robert H. Kraichnan and Vladimir E. Zakharov. The pair share the prize for their “distinct contributions to the theory of turbulence, particularly the exact results and the prediction of inverse cascades, and for identifying classes of turbulence problems for which in-depth understanding has been achieved,” says the ICTP.

Kraichnan, who has been a research agency grantee and a consultant to a variety of organizations since 1962, has done “pioneering research on field-theoretic approaches to turbulence and other non-equilibrium systems,” according to the ICTP. In particular, he has predicted the inverse energy cascade and forward enstrophy cascade in two-dimensional turbulence. He developed soluble, self-consistent dynamical models that shared invariances and conservation properties with the Navier–Stokes equation and gave quantitatively good predictions of low-order turbulence statistics. Central to this work is the direct-interaction approximation model. Kraichnan also introduced the “rapid change” model of advection of a scalar field by a random velocity field. For the first time in a turbulence-related problem, the model exhibited anomalous scaling that could be demonstrated analytically.

Zakharov, who directed the Russian Federation’s Landau Institute for Theoretical Physics in Moscow until this past June, has contributed to a deeper understanding of weak turbulence, which has broad physical applications to the theory of wind-driven waves in the ocean, to wave turbulence in the solar corona, and to the kinetics of Bose–Einstein condensation. His achievements include “putting the theory of wave turbulence on a firm mathematical ground by finding turbulence spectra as exact solutions and solving the stability problem, and in introducing the notion of inverse and dual cascades in wave turbulence,” says the ICTP. Zakharov is a professor of mathematics at the University of Arizona, Tucson.

The two medalists each received a $5000 cash prize.