Solving a Cosmic Conundrum: “Perfect Fluid” Brings Us Closer to Understanding How Our Universe Began

How to Catch a Perfect Wave: Scientists Take a Closer Look Inside the Perfect Fluid

Berkeley Lab research brings us closer to understanding how our universe began.

Scientists have reported new clues to solving a cosmic conundrum: How the quark-gluon plasma – nature’s perfect fluid – evolved into matter.

A few millionths of a second after the Big Bang, the early universe took on a strange new state: a subatomic soup called the quark-gluon plasma.

And just 15 years ago, an international team including researchers from the Relativistic Nuclear Collisions (RNC) group at Lawrence Berkeley National Laboratory (Berkeley Lab) discovered that this quark-gluon plasma is a perfect fluid – in which quarks and gluons, the building blocks of protons and neutrons, are so strongly coupled that they flow almost friction-free.

View time-lapse video clip showing a supersonic Mach wave as it evolves in an expanding quark-gluon plasma. The computer simulation provides new insight into how matter formed during the birth of the early universe. Credit: Berkeley Lab

Scientists postulated that highly energetic jets of particles fly through the quark-gluon plasma – a droplet the size of an atom’s nucleus – at speeds faster than the velocity of sound, and that like a fast-flying jet, emit a supersonic boom called a Mach wave. To study the properties of these jet particles, in 2014 a team led by Berkeley Lab scientists pioneered an atomic X-ray imaging technique called jet tomography. Results from those seminal studies revealed that these jets scatter and lose energy as they propagate through the quark-gluon plasma.

But where did the jet particles’ journey begin within the quark-gluon plasma? A smaller Mach wave signal called the diffusion wake, scientists predicted, would tell you where to look. But while the energy loss was easy to observe, the Mach wave and accompanying diffusion wake remained elusive.

This 2010 video describes collisions of heavy particles at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider. In 2005, RHIC physicists announced that matter created in the accelerator’s most energetic collisions behaves like a nearly perfect liquid. The properties of this fluid, the quark-gluon plasma, help us to understand the properties of matter in the early universe. Credit: Brookhaven National Laboratory

Now, in a study published recently in the journal Physical Review Letters, the Berkeley Lab scientists report new results from model simulations showing that another technique they invented called 2D jet tomography can help researchers locate the diffusion wake’s ghostly signal.

“Its signal is so tiny, it’s like looking for a needle in a haystack of 10,000 particles. For the first time, our simulations show one can use 2D jet tomography to pick up the tiny signals of the diffusion wake in the quark-gluon plasma,” said study leader Xin-Nian Wang, a senior scientist in Berkeley Lab’s Nuclear Science Division who was part of the international team that invented the 2D jet tomography technique.

To find that supersonic needle in the quark-gluon haystack, the Berkeley Lab team culled through hundreds of thousands of lead-nuclei collision events simulated at the Large Hadron Collider (LHC) at CERN, and gold-nuclei collision events at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Some of the computer simulations for the current study were performed at Berkeley Lab’s NERSC supercomputer user facility.

Wang says that their unique approach “will help you get rid of all this hay in your stack – help you focus on this needle.” The jet particles’ supersonic signal has a unique shape that looks like a cone – with a diffusion wake trailing behind, like ripples of water in the wake of a fast-moving boat. Scientists have searched for evidence of this supersonic “wakelet” because it tells you that there is a depletion of particles. Once the diffusion wake is located in the quark-gluon plasma, you can distinguish its signal from the other particles in the background.

Their work will also help experimentalists at the LHC and RHIC understand what signals to look for in their quest to understand how the quark-gluon plasma – nature’s perfect fluid – evolved into matter. “What are we made of? What did the infant universe look like in the few microseconds after the Big Bang? This is still a work in progress, but our simulations of the long-sought diffusion wake get us closer to answering these questions,” he said.

Reference: “Search for the Elusive Jet-Induced Diffusion Wake in Z/γ-Jets with 2D Jet Tomography in High-Energy Heavy-Ion Collisions” by Wei Chen, Zhong Yang, Yayun He, Weiyao Ke, Long-Gang Pang and Xin-Nian Wang, 17 August 2021, Physical Review Letters.
DOI: 10.1103/PhysRevLett.127.082301

Additional co-authors were Wei Chen, University of Chinese Academy of Sciences; Zhong Yang, Central China Normal University; Yayun He, Central China Normal University and South China Normal University; Weiyao Ke, Berkeley Lab and UC Berkeley; and Longgang Pang, Central China Normal University.

NERSC is a DOE Office of Science user facility at Berkeley Lab.

This work was supported by the DOE Office of Science and Office of Nuclear Physics.

Big BangBrookhaven National LaboratoryDOEPlasmaPopular
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  • Torbjörn Larsson

    In retrospect an early matter state that obeys the simplest cosmological descriptions may be a likelier initial state.

    “Perfect fluids are used in general relativity to model idealized distributions of matter, such as the interior of a star or an isotropic universe. In the latter case, the equation of state of the perfect fluid may be used in Friedmann–Lemaître–Robertson–Walker equations to describe the evolution of the universe.”

    [“Perfect fluid”, Wikipedia]

    In other news, more science news outlets are trying to pull readers into the discoveries of modern cosmology. Here is one recent coverage with an astronomer/astrophysicist, which while still extrapolating the hot big bang to far into the inflation era – i.e. getting the initial observable universe too small* – at least put the major implications correct: .

    “One of the biggest misconceptions in science is that the Big Bang came out of nothing – according to astrophysicist Michelle Thaller, this is not correct.

    13.8 billion years ago right before the Big Bang, our universe existed within one tiny, compressed atom. But what we know now is that this one atom was not our entire universe.

    According to Thaller, there were trillions of atoms, all with their own universe inside. Today, we can only know of our observable universe, but there is far more out there than what meets the eye.”

    * Inflation observations [c.f. the Planck observatory collaboration 2018 inflation paper] implies the early universe was far from the universal energy density limit – Planck energy density – so the volume of the observable universe as it came out of the inflation era and proceeded into the hot big bang era was about 1 cubic meter. Still small compared to today. 😉

    • Torbjörn Larsson

      *too far

      • xABBAAA

        …there, there Torblorn L…

  • mullach abu

    solving a cosmic conundrum
    i need clarity something before i can ask my question
    so which model are you using
    step 1 cosmologists do inform us
    in the first trillions of a second space expanded with an unknown scientific energetic force to the size of the observable universe the fabric of space is formed
    maybe the dark matter of the universe 75% of it maybe not
    a few millionths of a second after the big bang a subatomic soup called a quark gluon plasma appears hey presto like you know like
    and believe you me no cosmologist explains how the fabric of space with absolute nothing in it transforms itself into a quark gluon plasma perfect fluid
    as we have used up the dark energy into making the fabric of space what scientific name are you cosmologists giving this force the ability to make quark gluon from nothing
    abracadabra lets make a pea soup add three nails of two toads and hey
    step 2 cosmologists dont inform us
    now does your quark gluon plasma perfect fluid fill this entire fabric of space and eventually make ordinary matter 5% of the universe matter
    13.7 billion light years wide + quark gluon plasma in all of 13.7 bn ly
    25 billion light years wide + quark gluon plasma in all of 25 bn ly
    this we know this we are certain of we know 5% of the universe
    do you really want to know the rest warts and all ok read on
    step 3 cosmologists dont inform us
    as we look out today at this baryonic matter univere science is saying
    the total universe is 44 billion light years expanded with dark matter 75% baryonic matter 5 % and dark energy 20% and no quark gluon plasma present
    the observable universe is expanded 13.7 with no quark gluon plasma present and dark matter 75% baryonic matter 5% and dark energy 20%
    if you can clarify the above
    which model u are using
    i may then be able to direct my question accordingly

    • Torbjörn Larsson

      I think you are trying to describe the modern inflationary hot big bang cosmology.

      The high potential energy in the initial inflation quantum field was converted to the hot big bang at the end of inflation. There are some good videos in the series PBS Space and Time on that. For isnatnce, .

  • Howard Jeffrey Bender, Ph.D.

    This speculation for a quark=gluon plasma is fine, but there’s a bigger question about the creation of the universe.

    Surely you didn’t think all of the matter and energy we see now was stuffed in a single Big Bang! As you may know, quantum mechanics proposes a roiling quantum foam energy field everywhere in the universe, and the right kind of energy spikes creates string/anti-string pairs. These pairs immediately annihilate each other, but I suggest a process similar to Hawking radiation that form permanent strings that are the basis of all the matter and energy we have. This is a Big Bang/Big Crunch cycle, over and over. Interestingly, this same process can be used to form the galaxies we see. Gravity is far too weak to cause anything to combine rather than flying apart from the enormous force of the Big Bang. Specifics for the physical creation of the universe and the galaxies are shown in my YouTube

    • Torbjörn Larsson

      It would be a question to answer, except you always try to ‘answer’ with the same pseudoscience link no matter the topic.

  • Sarj

    Einstein relativity after the rapid expansion must mean that the perfect fluid was needed till individual mass held the know universe in place I theorise the start of the universe was due to the mass of it effects on distant unknown formed

    • Torbjörn Larsson

      It’s the same space, only expanded by way of general relativity [… ]. Put another way, the universe is all there is.

  • Sarj

    Inc Einsteins relativity ,after the rapid expansion ,the perfect fluid must be natural and needed to help create space till individual mass formations helped separate the soup and they eventually held the know universe in place. I theorise the start of the universe was due to the mass of it and its effects on distant unknown formed universe’ that again due to e=mc2 forced the formation known unknown universe within our 13.8b bn ly pocket. Not withstanding the speed limit of light adding up to 45 bn years to its depictions respectively.

  • BibhutibhusanPatel

    The problem of quark’gluon has solution.This point is encircled by the rings.These rings are nothing but the ñew physics with muons,experiments coducting at Fermi Lab. and CERN.Clue of perfect fluid is present in these experiments.

    • Torbjörn Larsson

      What does that even mean? What “point”?

  • BibhutibhusanPatel

    Thanks to the T.L.
    The point is that some of the energy
    or photos transform to magnetism,keeping gravity unchanged(inverse square law is exceptional).

  • BibhutibhusanPatel

    Thanks to the T.L.
    The point is that some of the energy
    or photos transform to magnetism,keeping gravity unchanged(inverse square law is exceptional).
    This is a property,by virtue of muon a cousin sister particle of electron.

  • BibhutibhusanPatel

    Thanks to the T.L.
    The point is that some of the energy
    or photos transform to magnetism,keeping gravity unchanged(inverse square law is exceptional).
    This is a property,by virtue of muon a cousin sister particle of electron.
    Central fact is this linked to some phnenomena in real physics to discovered.Also quark-gluon cañ be understood by such.So necessary is to work more.

  • Uryuxl

    We will never be closer to understanding how the universe began. There never was a begining.It has always been here and always will. You can’t get something from nothing. The Greeks knew that thousands of years ago. Energy can neither be created nor destroyed. It will always be here in this vast ocean of radiation energy. Changing from energy to matter at the rate of E=MC². That is all we see out there. Dont try to create something that isn’t there unless you’ve come up with a way to create something from nothing. Like to see that.