Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

When fluid flows almost as fast as light -- with quantum rotation

22.06.2018

Quark-gluon plasma is formed as a result of high energy collisions of heavy ions. After a collision, for a dozen or so yoctoseconds (that's 10-24 seconds!), this most perfect of all known fluids undergoes rapid hydrodynamic expansion with velocities close to the velocity of light. An international team of scientists, associated with the IFJ PAN and the GSI Centre, has presented a new model describing these extreme flows. Interestingly, for the first time effects resulting from the fact that the particles creating the plasma carry spin, that is, quantum rotation, are taken into account.

Each proton and each neutron is composed of several quarks bound by strong interactions carried by intermediary particles called gluons. When heavy ions built of protons and neutrons, accelerated to velocites very close to the velocity of light, collide with each other, they usually undergo destruction, transforming into an exotic fluid: quark-gluon plasma. Due to its negligible viscosity, this plasma is considered to be the most perfect fluid in the Universe.


Ultrarelativistic flow of quark-gluon plasma with spin. On the left, the initial state of the system, on the right -- the result of hydrodynamic evolution. The arrows on the bottom view show the plasma flow lines. The red area is the region of polarized particles that evolves according to the flow of matter. The top graphs show plasma temperature profiles. (Source: IFJ PAN)

Source: IFJ PAN

New experimental measurements, however, suggest that the particles leaving the plasma exhibit nontrivial arrangement of their spin directions. In order to explain these results, a group of scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow and the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt (Germany) has presented a new model of relativistic flows of quark-gluon plasma, taking into account the phenomena arising from the quantum spin of the particles forming it.

For about ten microseconds after the Big Bang, quark-gluon plasma filled the entire Universe. However, it rapidly cooled down and gluons stuck the quarks together into groups - the particles of which our world is built. As a result, quark-gluon fluid can today only be seen as the effect of high-energy collisions of heavy ions (and, possibly, also of smaller colliding systems consisting of protons and ions). Collisions of this type are currently being carried out in just a few accelerator centres in the world.

The flow of fluids and gases is dealt with in hydrodynamics, a field that has been under development for centuries. After the emergence of the theory of relativity, classical hydrodynamics was extended by relativistic phenomena, occurring when fluid flows at velocities close to the velocity of light. After the birth of quantum theory, with time, hydrodynamics can be extended by descriptions of the flow of particles with spin.

Spin is a feature of elementary particles associated with the properties of their wave functions relative to rotation. It can only take on discrete values, e.g. 0, 1/2, 1, 3/2, etc. The direction of spin of particles with spin 1/2 can be equal to +1/2 or -1/2 with respect to any axis. The non-zero polarization of particles with spin 1/2 means that the produced particles are more likely to take on one spin direction (+1/2 or -1/2).

"Hydrodynamics is an excellent tool for describing many physical phenomena. We have broadened its scope of applicability. We are the first to present a coherent description of relativistic particle flows with spin 1/2," explains Prof. Wojciech Florkowski (IFJ PAN, UJK, EMMI), who in collaboration with the group of Prof. Bengt Friman (GSI) has developed a new flow model.

Work on the model of relativistic flows with spin was inspired by recent measurements of the polarization of spins of particles known as Lambda hyperons (these are conglomerates of three quarks: up, down and strange, with a total spin of 1/2), recorded in heavy-ion collisions. Physicists have long been experimenting in trying to better understand the polarization of Lambda hyperons. The measurements, however, were subject to considerable uncertainty. Only recently in experiments carried out at the Brookhaven National Laboratory on Long Island near New York has it been shown that the spins of the Lambda hyperons formed in collisions of heavy nuclei are indeed polarized.

It has been known for a long time that the spin of a quantum object contributes to its total momentum. For example, in ferromagnetic materials, the Einstein-de Haas effect can be observed: when a non-polarized system is placed in a magnetic field, the spin of the particles it is composed of starts to orientate according to the magnetic field which means that to maintain the total angular momentum the system must begin to rotate. Observation of the polarization of the Lambda hyperons formed as a result of quark-gluon plasma transformations thus indicates the difficult to ignore role of spin in shaping the flow of this plasma.

The model presented by the group of physicists from IFJ PAN and GSI is a generalization of the hydrodynamics of perfect fluid. Since there is spin in the described systems, the principle of angular-momentum conservation should have been included in the theoretical description.

"Just as temperature is associated with the principle of conservation of energy, velocity with the principle of conservation of momentum, and electric potential with the principle of conservation of charge current, so in the systems described by us, spin polarization is associated with the principle of conservation of momentum. When you take this principle into account, you get additional equations, better describing the evolution of the system," explains Prof. Florkowski.

Quark-gluon plasma is such an exotic state of matter that for decades or even hundreds of years there will be no question of its technological applications. However, these studies have important implications today. Relativistic flows of particles with spin are in fact a new window to the world of strong interactions, which, among others, bind quarks in protons and neutrons. Thus, strong interactions play a very important role in the Universe, but they are extremely complicated to describe. Therefore, researchers hope that in relativistic flows with spin it will be possible to get to know these effects a little better.

###

This study was co-funded, among others, by the ExtreMe Matter Institute (EMMI), which operates at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt (Germany).

The Henryk Niewodniczanski Institute of Nuclear Physics (IFJ PAN) is currently the largest research institute of the Polish Academy of Sciences. The broad range of studies and activities of IFJ PAN includes basic and applied research, ranging from particle physics and astrophysics, through hadron physics, high-, medium-, and low-energy nuclear physics, condensed matter physics (including materials engineering), to various applications of methods of nuclear physics in interdisciplinary research, covering medical physics, dosimetry, radiation and environmental biology, environmental protection, and other related disciplines. The average yearly yield of the IFJ PAN encompasses more than 600 scientific papers in the Journal Citation Reports published by the Thomson Reuters. The part of the Institute is the Cyclotron Centre Bronowice (CCB) which is an infrastructure, unique in Central Europe, to serve as a clinical and research centre in the area of medical and nuclear physics. IFJ PAN is a member of the Marian Smoluchowski Krakow Research Consortium: "Matter-Energy-Future" which possesses the status of a Leading National Research Centre (KNOW) in physics for the years 2012-2017. The Institute is of A+ Category (leading level in Poland) in the field of sciences and engineering.

CONTACTS:

Prof. Wojciech Florkowski
The Institute of Nuclear Physics Polish Academy of Sciences
tel.: +48 12 6628469
email: wojciech.florkowski@ifj.edu.pl

SCIENTIFIC PAPERS:

"Relativistic fluid dynamics with spin"
W. Florkowski, B. Friman, A. Jaiswal, E. Speranza
Physical Review C 97, 041901(R)
DOI: https://doi.org/10.1103/PhysRevC.97.041901

LINKS:

http://www.ifj.edu.pl/
The website of the Institute of Nuclear Physics Polish Academy of Sciences.

http://press.ifj.edu.pl/
Press releases of the Institute of Nuclear Physics Polish Academy of Sciences.

IMAGES:

IFJ180621b_fot01s.jpg
HR: http://press.ifj.edu.pl/news/2018/06/21/IFJ180621b_fot01.jpg

Ultrarelativistic flow of quark-gluon plasma with spin. On the left, the initial state of the system, on the right - the result of hydrodynamic evolution.

The arrows on the bottom view show the plasma flow lines. The red area is the region of polarized particles that evolves according to the flow of matter. The top graphs show plasma temperature profiles. (Source: IFJ PAN)

Media Contact

Prof. Wojciech Florkowski
wojciech.florkowski@ifj.edu.pl
48-126-628-469

http://www.ifj.edu.pl/?lang=en 

Prof. Wojciech Florkowski | EurekAlert!

More articles from Physics and Astronomy:

nachricht Halfway mark for NOEMA, the super-telescope under construction
20.09.2018 | Max-Planck-Institut für Radioastronomie

nachricht What even Einstein didn't know
20.09.2018 | Technische Universität München

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists present new observations to understand the phase transition in quantum chromodynamics

The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.

This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.

Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...

Im Focus: Patented nanostructure for solar cells: Rough optics, smooth surface

Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.

"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...

Im Focus: New soft coral species discovered in Panama

A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.

Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...

Im Focus: New devices based on rust could reduce excess heat in computers

Physicists explore long-distance information transmission in antiferromagnetic iron oxide

Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.

Im Focus: Finding Nemo's genes

An international team of researchers has mapped Nemo's genome

An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

One of the world’s most prominent strategic forums for global health held in Berlin in October 2018

03.09.2018 | Event News

4th Intelligent Materials - European Symposium on Intelligent Materials

27.08.2018 | Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

 
Latest News

Glacial engineering could limit sea-level rise, if we get our emissions under control

20.09.2018 | Earth Sciences

Warning against hubris in CO2 removal

20.09.2018 | Earth Sciences

Halfway mark for NOEMA, the super-telescope under construction

20.09.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>