Препринты / Preprints

Since first reported in 1955 the Fermi — Pasta — Ulam (FPU) recurrence phenomenon has been thoroughly studied. Being reproduced in nonlinear electric lines this intermittent physical process became a possible instrument for a structural analysis. The FPU electromagnetic spectrum generated in coupled nonlinear lines proved to cover a wide band of frequencies (10 Hz — 10 GHz). Generator and a receiver of this spectrum have been developed and tested in different structures including water, electrolytes, oil, blood and biological tissues. The sample under examination was placed between the generator and receiver resonators of the FPU spectrum. Such a system was able to distinguish different oil and water samples. Combined with laser the FPU generator and receiver can be used for a distant (1 km) air search of oil beds.

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Equations of macroscopic hydrodynamics of normal 3He at low temperatures are obtained. Macroscopic theory is more convenient than kinetic one when specific problems are considered. Macroscopic description of 3He is based on two-velocity model, which means that mass and entropy can move each with its own velocity. The suggested macroscopic theory is valid for those Fermi liquids where higher order tensor branches of zero-sound cannot propagate on account of Landau fading. Contrary to superfluid liquid, independent movement of entropy and mass in normal Fermi liquid is hampered by certain force field arising when equilibrium distribution function of quasi-particles is perturbed (a kind of elasticity). Obtained equations provide a satisfactory description of both conventional and zero sound and also the recently discovered thermomechanical effect in 3He.

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