Madrid, 28 (Europe Press)
The quark-gluon plasma, the soup of elementary particles that formed microseconds after the Big Bang, shows striking similarities as a liquid with water that comes from our faucet.
This is the conclusion highlighted in a new study published in the journal SciPost Physics.
The relationship between a fluid’s viscosity and a measure of its amplitude and density determines how it flows. While both the viscosity and density of the quark-gluon plasma are about 16 times greater than that in water, the researchers found that the relationship between the viscosity and the density of the two types of fluids is the same.
This indicates that one of the most bizarre states of matter known to exist in our universe will flow from a tap in the same way as water.
The material that our universe is made of consists of atoms that consist of nuclei that have electrons revolving around them. The nuclei are made of protons and neutrons, collectively known as nucleons, and these in turn consist of quarks interacting with gluons. At very high temperatures, which are a million times higher than the temperatures in the centers of the stars, quarks and gluons are released from the parent nuclei, and instead form a hot, dense soup known as the quark-gluon plasma.
It is believed that shortly after the Big Bang, the early universe was filled with an incredibly hot quark-gluon plasma. This was then cooled by microseconds to form the building blocks of all matter within our universe.
Since the early 2000s, scientists have been able to experimentally reconfigure the quark-gluon plasma using large particle colliders, providing new insights into this strange state of matter.
The ordinary matter we encounter every day is thought to have properties completely different from the quark-gluon plasma found in the early universe. For example, liquids like water undergo the behavior of atoms and molecules that are much larger than the particles in the quark-gluon plasma and are held together by weaker forces.
However, a recent study shows that despite these differences, the relationship between viscosity and density, known as kinematic viscosity, is close in both quark-gluon plasmas and normal fluids. This relationship is important because fluid flow is not only dependent on viscosity, but is governed by the Navier-Stokes equation, which has density and viscosity. Therefore, if this relationship is the same for two different liquids, then these two fluids will flow in the same way even if they have very different viscosities and densities.
Importantly, it is not just any liquid viscosity that matches that of a quark-gluon plasma. In fact, the viscosity of a liquid can vary in several orders of magnitude depending on the temperature. However, there is a very special point at which the viscosity of the fluid is an almost universal minimum.
Previous research found that at this point, the viscosity of the fluid is governed by fundamental physical constants such as Planck’s constant and the mass of nucleons. It is these constants of nature that ultimately determine whether a proton is a stable particle and govern processes such as nuclear synthesis in stars and the creation of the basic biochemical elements necessary for life. The new study found that it is this global minimum viscosity for normal fluids such as water that turns out to be close to the viscosity of the quark-gluon plasma.
Professor Kostia Trachenko, professor of physics at Queen Mary University of London and author of the recent research paper, said in a statement: “We still do not fully understand the origin of this striking similarity, but we believe it could be related to the basic physical essence. Of ordinary liquids and a quark-gluon plasma.
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