# Physicists first calculated the yield point of a liquid

Russian and British scientists were the first to deduce one of the fundamental equations of physics, which makes it possible to theoretically calculate the limit to which a liquid remains a liquid. The equation is based on fundamental natural constants.

It is known that liquids become thicker when cooled and more liquid when heated. If you continue to heat them, the liquids begin to boil and turn into a gaseous state. At the transition point, which depends not only on temperature, but also on pressure, the liquid has a minimum viscosity. This is the yield point.

Traditionally, it is believed that viscosity cannot be calculated theoretically, since it depends in a complex way on the structure of the liquid, its composition, chemical interactions, and also on external conditions. Nobel laureate Steven Weinberg compared the difficulty of calculating the viscosity of water with the problem of calculating the fundamental physical constants that underlie the structure of our universe.

Despite all the difficulties, Kostya Trachenko from Queen Mary University of London and Vadim Brazhkin, a Russian scientist, director of the Institute for High Pressure Physics of the Russian Academy of Sciences, succeeded.

At the same time, in the yield stress equation obtained by scientists, two fundamental physical constants are used – measurable properties of physical nature that do not change – the minimum value of elementary viscosity, which is the product of viscosity and volume per molecule, and Planck’s constant, which governs the quantum world – the dimensionless ratio of the proton mass to the electron.

“This result is amazing,

– the words of Professor Kostya Trachenko are quoted in a press release from Queen Mary University of London. –Viscosity is a complex property that varies greatly for different fluids and environmental conditions. However, it turned out that the value of the minimum viscosity for all fluids can be simple and universal. ”

The discovery has real practical applications. First, the new equation will be useful in creating new ultra-low viscosity fluids for various chemical, industrial or biological processes. It will show the limit beyond which there is no point in striving, wasting resources. One example where this is important is the recent use of supercritical fluids for environmentally friendly methods of handling and dissolving complex waste.

Secondly, since the obtained limitation is fundamental, that is, it is based on basic physical constants, the discovery can be used to describe the processes taking place in the Universe as a whole, for example, to determine the so-called “habitable zone” where stars and planets can form, vital molecular structures emerge.

“There are indications that the fundamental lower limit of fluid viscosity may be related to very different areas of physics: black holes, as well as a new state of matter, quark-gluon plasma, which appears at very high temperatures and pressures. Exploring and evaluating these and other connections is what makes research so exciting. ”

– notes academician Brazhkin.

The article was published in the journal *Science Advances *

Source: ria.ru