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There's no speed limit in a superfluid universe. Now we know why.

Exotic particles stick to all surfaces in the superfluid, shielding it from interacting with the bulk superfluid.
Exotic particles stick to all surfaces in the superfluid, shielding it from interacting with the bulk superfluid.
(Image: © Lancaster University)

In the cold, dense medium of a helium-3 superfluid, scientists recently made an unexpected discovery. A foreign object travelling through the medium could exceed a critical speed limit without breaking the fragile superfluid itself.

As this contradicts our understanding of superfluidity, it presented quite a puzzle - but now, by recreating and studying the phenomenon, physicists have figured out how it happens. Particles in the superfluid stick to the object, shielding it from interacting with the bulk superfluid, thus preventing the superfluid's breakdown.

"Superfluid helium-3 feels like a vacuum to a rod moving through it, although it is a relatively dense liquid. There is no resistance, none at all," said physicist Samuli Autti of Lancaster University in the UK. "I find this very intriguing."

Superfluids are a type of fluid that has zero viscosity and zero friction, and therefore flows without losing kinetic energy. They can be made relatively easily from bosons of the helium-4 isotope, which, when cooled to just above absolute zero, slow down enough to overlap and form a high-density cluster of atoms that act as one 'super-atom'.

These 'super-atoms' form just one type of superfluid, though. Another is based on the boson's sibling, the fermion. Fermions are particles that include atomic building blocks like electrons and quarks.

When cooled below a certain temperature, fermions become bound together in what are called Cooper pairs, each made up of two fermions that together form a composite boson. These Cooper pairs behave exactly like bosons, and can thus form a superfluid.

The team created their fermionic superfluid out of helium-3, a rare isotope of helium missing one neutron. When cooled to one ten thousandth of a degree above absolute zero (0.0001 Kelvin, or -273.15 degrees Celsius/-459.67 degrees Fahrenheit), helium-3 forms Cooper pairs.

These superfluids are fairly fragile, and the Cooper pairs can break apart if an object moves through it above a certain velocity, called the critical Landau velocity.

And yet, in a 2016 paper, researchers from Lancaster University found that a wire rod moving through a helium-3 superfluid could exceed this velocity without breaking the pairs.

In their follow-up experiments, they measured the force required to move the wire rod through the superfluid. They measured an extremely small force when the wire started moving, but once it was moving, the force required to keep going was zero - just give it a nudge and off it goes.

The team concluded that the initial force comes from the Cooper pairs moving around a little to accommodate the motion, exerting that small starting force on the wire rod. But, after that, the wire can move freely, essentially camouflaged in a coat of Cooper pairs.

"By making the rod change its direction of motion we were able to conclude that the rod will be hidden from the superfluid by the bound particles covering it, even when its speed is very high," said physicist Ash Jennings of Lancaster University.

This new finding could have some interesting implications.

Fermionic superfluids can be used to create superconductors, which in turn are under investigation as a critical component of quantum computers. Knowing more about how and why superfluids behave the way they do is likely to only bring us closer to that goal.

The research has been published in Nature Communications.

This article was originally published by ScienceAlert. Read the original article here.

  • FB36
    What if spacetime of our whole universe is a certain kind of superfluid?

    This is a topic I really think I can provide useful guidance/direction to any interested theoretical physicists:

    The problem is how GR emerges from QM!
    Which is actually, how spacetime emerges from quantum vacuum!

    First realize, GR is fully compatible w/ spacetime being a (super)fluid:
    https://en.wikipedia.org/wiki/Fluid_solution
    Then, realize, the problem actually is, how spacetime superfluid (at macro-scale) created by GAS-like dynamics of virtual particles of quantum vacuum (at micro-scale)!
    (As an (much simpler) analogy, think about how air (gas) creates atmosphere/weather (fluid)!)

    (Of course, the main goal would be to express these ideas mathematically, to create a new theory of quantum-relativity (which is beyond me)!)
    Reply
  • TorbjornLarsson
    The clickbait title in no way refer to our universe. The simplest general relativistic model both has the observed universal speed limit and an ideal "fluid" which in a classic model is an interaction free ideal "gas". These are different things, which the observation of having particle isolation at walls in order to exceed the Landau velocity (the speed at which fluid excitations would attain negative energy).

    So it is a curious, but not breaking physics of superfluids or the universe.
    Reply
  • TorbjornLarsson
    FB36 said:
    What if spacetime of our whole universe is a certain kind of superfluid?

    Well, as I note in my comment on the article, it already is (as you later note) but the superfluid physics here is not relevant to our universe ...

    FB36 said:
    The problem is how GR emerges from QM! Which is actually, how spacetime emerges from quantum vacuum!

    ... so this is a side topic.

    And again, these things are separate problems. It may look like spacetime "emerges" from general relativity since classical general relativity describes spacetime "curvature" in the form of geodesics that massless particles follow. But they may simply be convenience tools without real physics instantation analogous to how other classical field theores describes field lines without real physical instantation. If quantum physics field theory describes general relativity particles will follow none of those but the wavefunction will describe volume filling Feynman path distributions in a path integral formulation - the particle may visit any of those paths.

    And in the simplest theory gravity is a field that we get from linearizing Einsteins equations, a field that in preliminary tests describe the full non-linear general relativistic model outcomes http://www.scholarpedia.org/article/Quantum_gravity_as_a_low_energy_effective_field_theory ].

    This plays nice with modern inflationary hot big bang cosmology, where we observe space to be on average flat over sufficiently large volumes, and both the latest inflation field characterization and the integrated cosmology results points to an eternal slow roll inflation multiverse slow roll inflation field; BOSS 2020 galaxy survey summary cosmology paper short lists Weinbergs multiverse as explanation for the observed low vacuum energy].

    In a flat universe the system can be approximated as a classical (non-relativistic) adiabatic free expansion, not doing any pressure work (since inflation sees to it that both fields are at a 0 K temperature and 0 K/J entropy vacuum, consistent with the 0 J*m^3 energy density of flat space*). That seems to suggest, like the naturally eternal inflation process, that spacetime has always been flat despite fulfilling a Lorentz condition which preserves the laws of gravity and all other quantum fields within it. Gravity is the weakest force and so covers all energy densities up to Planck scale of quantum particle fields, so must always play nice with the Lorentz condition. But it, like space and time, may always have been. For no particular reason.

    * It is a true vacuum in that sense, despite wanting to roll down to local vacuum energy universes, but it expands faster than the fluctuation mediated local roll downs which expands to unmeasurable volumes on the inflation expansion rate scale. It looks to me like it is a frustrated vacuum state, analogous to the magnetized state solid state magnets can take.

    And of course a quantum field vacuum can only roughly be at 0 K, the quantum fluctuations set a smallest possible temperature. And so on for other measures.
    Reply
  • dizzo
    Apparently helium 3 and helium 4 cannot freeze even at absolute zero kelvin - if this is true then the universe will always have motion and cannot go back to a static motionless state from now on.
    When the Universe started to fall:
    The Gravitational Instability Cosmological Theory on the Formation of the Universe.
    The Theory:
    (1) The expansion of the universe is a result of the " heat ' contained therein;
    (2) The source of the " heat " is the cosmic microwave radiation background at 3 kelvin,
    wherein;
    (3) The microwave electro magnetic-nuclear energy was formed as a result of the
    interaction of two different static gravitational vacuum fields, causing gravitational
    instability and the motion, void of matter, at this time, wherein; static gravitational
    field (1) began to go into "motion".

    Therefore; the interaction of (2) motionless / static gravity vacuum fields, could eventually create dust particles in the Universe that later form into stars, galaxies , planets, moons and other objects in or about their current locations.

    Q: When did this motion start?
    A: If a neutral particle is able to resist the universal motion, in theory, that particle
    would go back in time. Going back in time the neutral particle would then enter into (1)
    of the (2) motionless-static gravity vacuum fields void of motion, and cause an unbalance
    and gravitational instability and this interaction would create motion and energy
    particles.
    Therefore; the interaction of (2) motionless / static gravity vacuum fields, ( now thanks to Mr Peebles, one Baryonic gravity vacuum field and one Non Baryonic vacuum field ) could eventually create dust particles in the Universe that later form into stars, galaxies , planets, moons and other objects in or about their current locations.

    Q: What causes a gravitational static vacuum field in the first place ?
    A: Pressure force is used to create a vacuum on Earth, perhaps an exotic something
    100,000 times weaker than the force of gravity decays, causing a static-motionless gravity vacuum field.

    Q: What created the motionless gravity vacuum fields in the first place ?

    A: Vacuums are created by pressure so the only answer I can think of is a created gravity vacuum pressure from the future goes back in time to start motion in the past.
    theory needs improvement - help yourself )


    They say the expanding balloon story often, but if the expanding balloon can be measured then it has a center. As for the rest of the theory, sending a man made particle back in time, ( the decay of a Higgs Muon ? ) maybe at CERN is pseudo science and even if possible, how could a tiny particle cause gravitational instability of 2 vacuum gravity fields of absolute zero 13.8 billion plus years ago that then interacts and generates a microwave background field that then creates dust particles that clump to form stars and galaxies and causes one field to fall. ...I'm not happy with the theory. but to say I should except a perpetually HOT blob that eventually expands and creates all the galaxies and has no place of occurrence other than everywhere is an even worse theory. ( an always hot blob ? )


    "but to say I should except a perpetually HOT blob that eventually expands and creates all the galaxies and has no place of occurrence other than everywhere is an even worse theory"
    The universe is not hot now, so the perpetually hot blob is a wrong idea. But where did you get this from? Why is this a candidate idea for the start of the Universe?

    That is a summary of the Big Bang Theory. Actually the universe if hot at 3 kelvin for the billion ly + size of it 3 kelvin is impressive. The CERN collider operates at 2 kelvin, my question is when was the last time the universe was at 2 kelvin ? ( Some Big Bang theorist would say never. )



    see the Neutroid Steady State Theory or
    The Steady State Galaxy Theory

    at

    RUFUS'S GALAXY WEB PAGE

    http://www.roycaswell.co.uk...

    The Steady State Galaxy Theory
    An Alternative To
    The Big Bang Theory

    --------------------------------------------------

    Here is a completely different cosmological theory - it too has problems such as it does to explain cosmic inflation, ( the Redshift ) the microwave background , and claims galaxies do not decay, other than this it is a thoughtful theory and i agree based on helium 4 as helium 3 and 4 cannot freeze ( decay ) the universe is I say 4x older than 13.8 billion years old and having a Neutroid instead of a back hole in the center of some galaxies makes sense too. I've seen Hubble galaxy photos with both a hole ) funnel ) and a neutroid ( ball of light ) in galaxy centers so it is up to debate
    Reply
  • TorbjornLarsson
    dizzo said:
    Apparently helium 3 and helium 4 cannot freeze even at absolute zero kelvin - if this is true then the universe will always have motion and cannot go back to a static motionless state from now on.

    Again, the paper and the article is not about our universe, despite the click bait title - you likely did not read either and is not interested in the presented science.

    A quantum particle field, as all the universe forces and matter seem to be constituted of, have always fluctuations even if a perfect vacuum https://en.wikipedia.org/wiki/Vacuum_state ].

    dizzo said:
    When the Universe started to fall:
    The Gravitational Instability Cosmological Theory on the Formation of the Universe. The Theory: (1) The expansion of the universe is a result of the " heat ' contained therein;
    (2) The source of the " heat " is the cosmic microwave radiation background at 3 kelvin,
    wherein;
    (3) The microwave electro magnetic-nuclear energy was formed as a result of the
    interaction of two different static gravitational vacuum fields, causing gravitational

    I'm not sure what "started to fall" means, though it is true that a classical newtonian gravity model of the expansion derives it as analogous to a thrown mass (for the matter dominated era), c.f. cosmologist Susskind's cosmology lectures at Stanford's open web courses.

    That leads up to that the expansion scale factor as a function of time develops depending on the inner energy state of the universe https://en.wikipedia.org/wiki/Scale_factor_(cosmology) ; note that the matter dominated era scale factor alpha(t) ~ t^2/3 describes precisely a parabola of a thrown mass].

    The radiation dominated era between the hot big bang start and about 50 kyrs, until dilution made the universe enter the matter dominated era for a couple of billion years (we are now in the dark energy dominated era) could be said to be driven by the universe "heat" at temperatures ranging from close to Planck temperature down trending towards the ~ 3,000 K when cosmic background radiation was released at ~ 400 kyrs. (Which now with space expanded by a factor ~ 1,000 has stretched cosmic background photons to a radiation temperature of ~ 3 K.)

    That is far from your quantitative description, and any correspondence with reality stops there. E.g. there is only one type of gravity field.

    dizzo said:
    That is a summary of the Big Bang Theory. Actually the universe if hot at 3 kelvin for the billion ly + size of it 3 kelvin is impressive. The CERN collider operates at 2 kelvin, my question is when was the last time the universe was at 2 kelvin ? ( Some Big Bang theorist would say never. )

    No, it obviously isn't https://en.wikipedia.org/wiki/Big_Bang ].

    And it is better described today as inflationary hot big bang cosmology P1Q8tS-9hYoView: https://www.youtube.com/watch?v=P1Q8tS-9hYo; the manuscript source is the popular astrophysicist Katie Mack]. One of the reasons for that is how the inflation that precedes the hot big bang period explains both the flatness and the homogeneity and isotropy of space, which only an expansion cannot .

    The universe has never before been at 2.7 K, obviously.

    dizzo said:
    Here is a completely different cosmological theory

    That link, if not the description, takes me to a pseudoscience site, with superstition thrown in for good measure.

    So no, it isn't "a theory" at a guess. Even if there were some reasonable numbers in a meaningless attempt at quantification of the absurd. it couldn't be published (hence the site).
    Reply
  • dizzo
    RUFUS'S GALAXY WEB PAGEThe Steady State Galaxy TheoryAn Alternative ToThe Big Bang Theory

    http://www.roycaswell.co.uk/Steady%20State%20Galaxy%20Theory%20by%20Rufus%20Young.htm
    " The Steady State Galaxy Theory overcomes the problem Hoyle had with his steady state theory while at the same time does not have the problems which the Big Bang Theory has. "
    Reply
  • Ralph Dratman
    It's too bad our world is not usually at cryogenic temperatures. If it were, we could use all sorts of effects like superconductivity and superfluidity all the time. That would change our lives immensely. Maybe at some point physicists will find out how to make these fascinating states of matter occur at temperatures closer to our everyday room temperature. If that ever happens, we might have many additional tools to deal with climate change.
    Reply
  • dizzo
    Bose–Einstein condensate from Wikipedia:
    Bosons, which is a group of particles that includes the photon as well as atoms such as helium-4 (4 He), are allowed to share a quantum state. Einstein proposed that cooling bosonic atoms to a very low temperature would cause them to fall (or "condense") into the lowest accessible quantum state, resulting in a new form of matter.

    In 1938, Fritz London proposed the BEC as a mechanism for superfluidity in 4 He and superconductivity.

    On 5 June 1995, the first gaseous condensate was produced by Eric Cornell and Carl Wieman at the University of Colorado at Boulder NIST–JILA lab, in a gas of rubidium atoms cooled to 170 nanokelvins (nK). Shortly thereafter, Wolfgang Ketterle at MIT realized a BEC in a gas of sodium atoms. For their achievements Cornell, Wieman, and Ketterle received the 2001 Nobel Prize in Physics. These early studies founded the field of ultracold atoms, and hundreds of research groups around the world now routinely produce BECs of dilute atomic vapors in their labs.

    Since 1995, many other atomic species have been condensed, and BECs have also been realized using molecules, quasi-particles, and photons.




    Experimental observationSuperfluid helium-4
    In 1938, Pyotr Kapitsa, John Allen and Don Misener discovered that helium-4 became a new kind of fluid, now known as a superfluid, at temperatures less than 2.17 K (the lambda point). Superfluid helium has many unusual properties, including zero viscosity (the ability to flow without dissipating energy) and the existence of quantized vortices. It was quickly believed that the superfluidity was due to partial Bose–Einstein condensation of the liquid. In fact, many properties of superfluid helium also appear in gaseous condensates created by Cornell, Wieman and Ketterle (see below). Superfluid helium-4 is a liquid rather than a gas, which means that the interactions between the atoms are relatively strong; the original theory of Bose–Einstein condensation must be heavily modified in order to describe it. Bose–Einstein condensation remains, however, fundamental to the superfluid properties of helium-4. Note that helium-3, a fermion, also enters a superfluid phase (at a much lower temperature) which can be explained by the formation of bosonic Cooper pairs of two atoms (see also fermionic condensate).
    Reply
  • dizzo
    When the universe started to fall; fall in this case means the following:

    quote : " Einstein proposed that cooling bosonic atoms to a very low temperature would cause them to fall (or "condense") into the lowest accessible quantum state, resulting in a new form of matter. "

    Bose–Einstein condensate from Wikipedia:

    Bosons, which is a group of particles that includes the photon as well as atoms such as helium-4 (4 He), are allowed to share a quantum state. Einstein proposed that cooling bosonic atoms to a very low temperature would cause them to fall (or "condense") into the lowest accessible quantum state, resulting in a new form of matter.

    In 1938, Fritz London proposed the BEC as a mechanism for superfluidity in 4 He and superconductivity.




    TorbjornLarsson said:
    Again, the paper and the article is not about our universe, despite the click bait title - you likely did not read either and is not interested in the presented science.

    A quantum particle field, as all the universe forces and matter seem to be constituted of, have always fluctuations even if a perfect vacuum https://en.wikipedia.org/wiki/Vacuum_state ].



    I'm not sure what "started to fall" means, though it is true that a classical newtonian gravity model of the expansion derives it as analogous to a thrown mass (for the matter dominated era), c.f. cosmologist Susskind's cosmology lectures at Stanford's open web courses.

    That leads up to that the expansion scale factor as a function of time develops depending on the inner energy state of the universe https://en.wikipedia.org/wiki/Scale_factor_(cosmology) ; note that the matter dominated era scale factor alpha(t) ~ t^2/3 describes precisely a parabola of a thrown mass].

    The radiation dominated era between the hot big bang start and about 50 kyrs, until dilution made the universe enter the matter dominated era for a couple of billion years (we are now in the dark energy dominated era) could be said to be driven by the universe "heat" at temperatures ranging from close to Planck temperature down trending towards the ~ 3,000 K when cosmic background radiation was released at ~ 400 kyrs. (Which now with space expanded by a factor ~ 1,000 has stretched cosmic background photons to a radiation temperature of ~ 3 K.)

    That is far from your quantitative description, and any correspondence with reality stops there. E.g. there is only one type of gravity field.



    No, it obviously isn't https://en.wikipedia.org/wiki/Big_Bang ].

    And it is better described today as inflationary hot big bang cosmology P1Q8tS-9hYoView: https://www.youtube.com/watch?v=P1Q8tS-9hYo; the manuscript source is the popular astrophysicist Katie Mack]. One of the reasons for that is how the inflation that precedes the hot big bang period explains both the flatness and the homogeneity and isotropy of space, which only an expansion cannot .

    The universe has never before been at 2.7 K, obviously.



    That link, if not the description, takes me to a pseudoscience site, with superstition thrown in for good measure.

    So no, it isn't "a theory" at a guess. Even if there were some reasonable numbers in a meaningless attempt at quantification of the absurd. it couldn't be published (hence the site).
    Reply
  • TorbjornLarsson
    dizzo said:

    dizzo said:

    dizzo said:
    When the universe started to fall; fall in this case means the following:
    quote : " Einstein proposed that cooling bosonic atoms to a very low temperature would cause them to fall (or "condense") into the lowest accessible quantum state, resulting in a new form of matter. "

    When you references to specific quotes, you may want to use the full reference ("fall into the lowest accessible quantum state") and add the quote. But our universe is obviously not a condensate nor at a lowest accessible state, as evidenced by us writing this.

    None of this has anything to do with a cosmological claim, as I pointed out at the start. The article has some science that can be discussed, but none of it is cosmology. If you are interested in current cosmology, the video I posted a link to is a pity summary (with no mechanisms, but I gave such references that those can be found in case it is your interest).

    And please stop linking to pseudoscience, superstition or other known erroneous ideas if you are on a science site - they don't belong here.
    Reply