°
Newark

Russian scientists have discovered a new physical paradox

Scientists from St. Petersburg Polytechnic University Peter the Great (Spbpu) found and theoretically explained a new physical effect, the essence of which consists in the possibility of growth of the amplitude of mechanical vibrations of an object without any external influence. In addition, they suggested that if the paradox of Fermi-Pasta-Ulam-Tsingou.

In SPbSPU is explained by a simple example: to rock the swing, they need to constantly push. It was believed that without continual external influence to achieve vibrational resonance is impossible.

However, the scientific team of the Higher school of theoretical mechanics, Institute of applied mathematics and mechanics of Spbpu discovered a new physical phenomenon – ballistic resonance, in which mechanical vibrations can be excited solely by internal heat system resources.

The key to understanding the began the experimental work of scientific groups around the world, show that in ultra-pure crystalline materials on the nano - and micro-level heat is distributed with abnormally high speed. This phenomenon is called ballistic conductivity.

The scientific group under the leadership of corresponding member of RAS Anton Krivtsov took the equations describing this phenomenon, and have made significant progress in the understanding of thermal processes on the micro-scale. In a study published in the scientific journal "Physical Review E", the researchers examined the behavior of systems with periodic initial temperature distribution in the crystalline material.

The phenomenon is that the alignment process heat leads to mechanical oscillations with increasing amplitude. The effect is known as ballistic resonance.

These discoveries also give the possibility of resolving the paradox the Fermi-Pasta-Ulam-Scurvy. In 1953, the scientific team led by Enrico Fermi conducted who later became a famous computer experiment. Scientists have considered the simplest model of oscillations of a chain of particles connected by springs. It was assumed that mechanical movement will gradually fade, turning into chaotic heat fluctuations, but the result was unexpected: fluctuations in the chain first has almost faded, but then was revived and almost reached the initial level. The system came in the initial state and the cycle is again repeated. The causes of mechanical vibrations of heat in the system for decades are the subject of research and debate.

The amplitude of the mechanical vibrations caused by the ballistic impact does not increase indefinitely, but reaches a maximum and then gradually decrease to zero. Over time, mechanical vibrations are damped completely, and the temperature is aligned along the crystal. This process is called thermalization. For engineers and physicists this experiment important for the reason that the chain of particles connected by springs is a good model of a crystalline material.

Researchers from the Higher school of theoretical mechanics of Spbpu showed that the transition of mechanical energy into heat occurs irreversibly, if we consider the process at finite temperature.

"Usually not taken into account that in real materials, along with the manual, there is thermal motion, the energy of which is several orders of magnitude higher. We recreated these conditions in the computer experiment showed that the thermal motion dampens mechanical wave and preclude the revival of fluctuations," – said the Director of the Higher school of theoretical mechanics of SPbSPU, corresponding member of RAS Anton Krivtsov.

According to experts, the theoretical approach proposed by scientists of SPbSPU, is a new way to look at what is meant by heat and temperature, and can be fundamental in the development of nanoelectronic devices of the future.