Isadore Rudnick

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Isadore Rudnick (born May 8, 1917 in New York City , † August 22, 1997 ) was an American physicist.


Rudnick studied physics at the University of California, Los Angeles (UCLA), with a bachelor's degree in 1938, a master's degree in 1940, and a doctorate in 1944. He was a post-doctoral student at Duke University , was an assistant professor at Pennsylvania State University, and returned in 1948 back to UCLA, where he remained as a professor until his retirement.


He is known for research into acoustics. He began in the 1940s with studies of sound propagation in the atmosphere, in the ground and non-linear effects of shock waves in canals and horns. Together with Clayton Allen at Pennsylvania State University, he developed the most intense sound source at the time, a siren, which was used to study the biological effects of sound and for acoustic techniques for cleaning clothes. At UCLA he studied acoustic induced currents, vibration modes of elastic bodies and the propagation of sound in seawater.

After a stay at the Technical University of Denmark in 1956, he turned to low-temperature physics and used ultrasound to investigate electron-phonon interactions in metals and superconductors. In the 1960s he turned to the hydrodynamics of superfluid helium, a topic that occupied him experimentally for the next twenty years. He and his group discovered two of the six sound modes in liquid helium.

He began with experiments on the 1st sound (corresponding to normal sound) at the superfluid transition ( lambda point ), in particular for the experimental determination of the relaxation of the order parameter. His group was the first to observe sound of the fourth type and used it to determine the decay of superfluid currents. He also investigated the third sound (a surface wave of thin films of superfluid helium), which he did not discover, but developed simple techniques for its generation and observation. In 1969 he observed the disappearance of fashion with the thickness of the helium film in a phase transition, later identified as the Kosterlitz-Thouless transition and examined more closely by Rudnick in this context, which remained one of the best experimental investigations of this transition. In 1969 he developed techniques for observing the second sound in liquid helium (with which heat spreads there) by vibrating a porous foil. With his group he systematically investigated the speed of the first, second and fourth sound at 400 points in the pressure-temperature phase diagram of liquid helium and they measured the thermodynamic properties with high accuracy.

Most recently, he dealt with gravity waves in shallow water and their non-linear aspects, studying bifurcation phenomena with his group and discovering a new kind of soliton in a standing wave.

At UCLA, he was also known for his lecture experiments and public demonstration experiments.

Honors and memberships

In 1981 he received the Fritz London Memorial Prize . In 1983 he became a Fellow of the National Academy of Sciences . In 1948 he received the Biennial Award from the Acoustical Society of America , its first silver medal in physical acoustics in 1975 and its gold medal in 1982.

Individual evidence

  1. In which the normal liquid component spreads in a porous medium
  2. Rudnick Critical surface density of the superfluid component in 4 He films , Phys. Rev. Lett., Vol. 40, 1978, pp. 1454-1455

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