What is Superfluid: Definition and 37 Discussions

Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two isotopes of helium (helium-3 and helium-4) when they are liquefied by cooling to cryogenic temperatures. It is also a property of various other exotic states of matter theorized to exist in astrophysics, high-energy physics, and theories of quantum gravity. The theory of superfluidity was developed by Soviet theoretical physicists Lev Landau and Isaak Khalatnikov.
Superfluidity is often coincidental with Bose–Einstein condensation, but neither phenomenon is directly related to the other; not all Bose–Einstein condensates can be regarded as superfluids, and not all superfluids are Bose–Einstein condensates.

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  1. Quantum23

    A What is gravity in the superfluid vacuum model of quantum gravity?

    It has been hypothesized by quantum field theory that the vacuum is not empty due to the energy time uncertainity relationship. Instead it is filled with a sea of virtual particles popping in and out of existence and renormalized to the observed value we see today in experiments like the casimir...
  2. C

    A Please help me understand this HO energy in He4 gas

  3. K

    I Quantized vortices in superfluid

    I am doing a final year project on vortex interactions and have searched for several research articles about quantum hydrodynamics. Most said that ''Any rotational motion of a superfluid is sustained only by quantized vortices.'' Is this something provable from the Gross-Pitaevskii Equation or...
  4. R

    B Proper Time Change: Helium 4 Superfluid Effects

    When helium 4 becomes a super fluid does the proper time change, can this be detected?
  5. J

    B Superfluid Helium and its use at CERN

    Hi, Wikipedia says CERN uses 100 gallons of superfluid helium 4 to cool its superconducting magnets. Why use superfluid helium 4 (2K) as apposed to regular liquid helium (4.2K). As far as I can see from Internet sources, the helium serves to keep the magnets in order to keep them in a...
  6. Superfluid universe

    A What Other Symmetries Exist in Superfluids?

    I am reading "Introduction to superfluidity" by Andreas Schmitt. He mentions the global symmetry U(1). What other symmetries are there in superfluids? Thank you.
  7. M

    A "UV completion of a theory of Superfluid Dark Matter"

    http://arxiv.org/abs/1801.04083 UV completion of a theory of Superfluid Dark Matter Andrea Addazi, Antonino Marciano (Submitted on 12 Jan 2018) We show that a model of superfluid dark matter, modifying the Newtonian potential and explaining galactic rotational curves, can be unitarized by the...
  8. K

    I Testing Quantum Gravity paper Bose Einstein helium superfluid

    Testing Quantum Gravity Johan Hansson, Stephane Francois (Submitted on 19 Oct 2017) The search for a theory of quantum gravity is the most fundamental problem in all of theoretical physics, but there are as yet no experimental results at all to guide this endeavor. What seems to be needed is a...
  9. Ken Gallock

    I What does it mean: "up to total derivatives"

    Hi. I don't understand the meaning of "up to total derivatives". It was used during a lecture on superfluid. It says as follows: --------------------------------------------------------------------- Lagrangian for complex scalar field ##\phi## is $$ \mathcal{L}=\frac12 (\partial_\mu \phi)^*...
  10. CMJ96

    Prove The Following Obeys Hamilton's Equation....

    Homework Statement Homework Equations Given in the above picture The Attempt at a Solution I have tried to rearrange the relationship between P and R to gain an expression for R, in terms of P. I subbed that into the expression for E and attempted to differentiate. I ended up with this...
  11. CMJ96

    What happens at the lambda point of superfluid Helium?

    Homework Statement 2. Homework Equations are given in the above picture 3. The attempt at the solution In part a) I simply rearranged the other expressions given and subbed them into the relationship for relative velocity and came out with Vns= Qdot/ρsT(1- ρn/ρs).Then in part b) I started by...
  12. R

    Is a Superfluid Perpetual Motion Machine Theoretically Possible?

    Yes, I'm aware of the countless threads about perpetual motion here. Not sure if this idea has been considered with superfluids, though. I'm no physics expert (basically a laymen), but the idea of a superfluid in perpetual motion intrigues me because I can't imagine why it wouldn't be possible...
  13. bcrowell

    Old video showing superfluid helium

    I thought this was pretty cool: www.youtube.com/watch?v=sKOlfR5OcB4 You can skip about the first 2 minutes, which are just the credits and some footage of them transferring some fluid. Nice concrete demonstration of various fun stuff such as superfluidity and second sound.
  14. H

    Superfluid Dark Matter: A Review of Theory & Evidence

    http://arxiv.org/pdf/1507.01019v1.pdf What do you think? Not published yet, but one of the authors is a postdoc at Princeton and the other a Princeton PhD and prof at U Penn so they might know something. As far as I know, the superfluid dark matter theory is deprecated because models of the...
  15. wolram

    So my question would be: Is Dark Matter a superfluid?

    This the best description of Dark Matter i have come across, it uses the LCDM and MOND to create a best fit model. arXiv:1507.03013 [pdf, other] A Dark Matter Superfluid Justin Khoury Comments: 8 pages. To appear in the proceedings of the 2015 Rencontres de Moriond, "Gravitation: 100 years...
  16. J

    What happens when Bose-Einstein Condensate exits a vacuum?

    I haven't learned about this yet in school but I'm assuming as the atoms condense down to a single wavelength the volume of the liquid would be very small. If this condensate was instantly released out of a vacuum and into normal atmospheric pressure, would the volume rapidly expand? Secondly...
  17. S

    Why does superfluid helium in a spinning bucket have angular momentum?

    Suppose you have a bucket filled with superfluid Helium-4 and you spin it with a large angular velocity Ω, the bucket obviously has angular momentum. Spinning fast enough, the fluid develops irrotational vortex lines which carry quanta of angular momentum, while leaving the curl of the ∇xv 0...
  18. H

    Rotation in a rotating superfluid

    Suppose you have a body floating in a rotating superfluid. Maybe a speck of dust. Would it rotate? What if you have two bodies connected in some way. Would this system rotate around its center of mass?
  19. G

    Books/information over superfluid vacuum theory

    Hi everybody, I do not really know if this thread belongs here, it just seemed to me the right place to ask. I don't know if there's a section to ask for books, if so I couldn't find it. I would like to know more about superfluid vacuum theory (SVT). I am finishing my physics BSc in june, so...
  20. S

    Atomtronics & Superfluid Circuits

    An atomic SQUID has been created from a superfluid circuit: http://jqi.umd.edu/news/first-controllable-atom-squid What are the applications of this? If you could have a superfluid coil, then could it generate some kind of field, like the way an electric coil does? Given that the...
  21. J

    What would happen if a big superfluid cloud eclipses the Sun?

    Imagine a big superfluid cloud the size of the Moon, at the same distance of the Moon in front of the Sun. A total eclipse of 7 minutes. What would happen with the light coming from the sun during these 7 minutes? Would we see a "night sun"? Another question. "Estimates of the photon...
  22. W

    The Superfluid Nature of Helium: Why Does It Refuse to Freeze?

    What prevents helium from becoming solid at normal atmospheric pressure? All other elements are solid at 0K, why does helium stay a superfluid liquid?
  23. W

    Why Is Normal Density Nonzero at Zero Temperature in Disordered Systems?

    By Landau's theory the normal mass density(total density minus the superfluid mass density) is the total mass carried by excitations. For the BCS state and weakly interacting Bose gas the normal density is zero at zero temperature because there are no excitations. However in the presence of...
  24. N

    What do we mean by broken symmetries when referring to superfluid he3 phases?

    What do we mean by "broken symmetries" when referring to superfluid he3 phases? I struggle to understand the concept of broken symmetries of the superfluid phases of 3He. Any insight would be much appreciated. Thanks :)
  25. I

    Airfoil lift in superfluid flow

    A superfluid has zero viscosity. Lift of an airfoil (and any shape for that matter) is zero without fluid viscosity. So, superfluids shouldn't generate lift when flowing around an airfoil. Is that true? I think it is impossible for a superfluid not to generate lift on an airfoil, because...
  26. T

    Experimentally observed properties of liquid 3He as a superfluid

    Hey everyone, I'm currently taking a thermal physics course and have been assigned a research paper about the thermodynamically arguable aspects of experimentally observed properties of the 3He superfluid. I have been searching for many different sources but have only found a few worthwhile...
  27. M

    Electrical properties of Superfluid helium

    I know there is a connection with the thermal conductive properties of a material and the electrical conductive properties, so I'm curious as to the electrical conductivity of superfluid helium (below the lambda point).
  28. S

    How is superfluidity in liquid helium explained by quantum mechanics?

    So I was checking out some cool videos on youtube of helium in superfluid state and I have a question about it. How exactly does this superfluid have both zero and non-zero viscosity at the same time? The evidence seems pretty clear that it exhibits zero viscosity since it forms a Rollin...
  29. E

    Can Anything Float in a Superfluid?

    Would a ship float in a superfluid? Would anything float in a superfluid? I think, that the frictionless behavior of the superfluid would prevent anything from floating, because it just can't "grab" to anything, would be like vacuum, no? Yes, ships float because they displace volume of water...
  30. A

    Quantized Vortices in Superfluid Rotation

    I am trying to derive an expression for the number of quantized vortices created in superfluid He-4 when a container of radius R is rotated at angular velocity 'omega'. I have completed an earlier part of the question, whereby I showed that the velocity of the superfluid as a function of r...
  31. A

    Wave Equation for Second Sound in Superfluid He-4

    I am trying to derive the wave equation for 'Second Sound in superfluid Helium-4 using the basic tenets of the two-fluid model. I am following the derivation in a book which has intermediate steps along the way - I am trying to fill in the gaps. I am almost there - there is only one step that I...
  32. G

    If helium is 'superfluid' at low temperatures

    if helium is 'superfluid' at low temperatures then is it correct to think of amorphous solids as 'superviscous'?
  33. M

    Are BECs superfluid or vice versa or what?

    I'm a physicist doing a course on condensates, superfluidity and superconductivity and I'm confused as to how these states overlap. Are all BECs necessarily superfluid? Are all superfluids necessarily BECs? The literature is incredibly ambiguous :frown:
  34. G

    Properties of superfluid Helium

    h ttp://en.wikipedia.org/wiki/Superfluid Wikipedia states that, in the context of superfluids: I assume what is meant is that the atoms have bosonic an fermionic properties under super-cooled conditions. I gather that the spin of the constituents of the atom (protons, neutrons...
  35. S

    Exploring Superfluidity: Macroscopic Quantity and Photographic Possibilities

    What is the biggest quantity of superfluid that has ever been made so far? Is it in the "macroscopic" range? Will the superfluidity be destroyed by photographing the stuff? Can one get a snapshot of it creeping up the bucket's wall, etc?
  36. R

    Does Superfluid Helium Behave as a Single Particle with Unified Spin?

    In a superfluid a small volume of liquid can be considered to behave as a single particle.Does this mean that ,for example,one cm^3 of helium-4 atoms has a total spin of 2?
  37. S

    Superfluid model of quantum gravity?

    Superfluid model of quantum gravity? This article is from the new Scientific American online magazine. Everything (and MUCH MORE) that the physicists in this article are explaining as a simple tentative direction of study has already been fleshed out in Sorce Theory. see...
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