A flow with no viscosity

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4answers
741 views

What is the Difference between a Lepton and a Fermion?

As the Title Says: I am Wondering what the Difference between a Lepton and A Fermion is. I know they both have an ½ integer spin number e.g. a electron, an atom with an odd mass number such as ...
1
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1answer
42 views

How two prove the second sound velocity is $1/\sqrt{3}$ times than the first sound [closed]

From Landau two hydrodynamics model in superfluid, we have the result $c_1^2=\frac{\partial P}{\partial \rho}|_T$ and $c_2^2=\frac{\rho_s s^2 T}{\rho_n c}$. In the zero temperature limit, how to ...
1
vote
1answer
65 views

Superfluid rotating frame of reference

I'm currently studying a text about Bose-Einstein condensates (BECs) and vortices. When they want to study whether a vortex will be formed, they look at the fact wether it's enegetically favorable. ...
3
votes
1answer
54 views

Superfluid $\Leftrightarrow$ Bose-Einstein condensate?

On the Wikipedia page on superfluidity one can find the sentence not all Bose-Einstein condensates can be regarded as superfluids, and not all superfluids are Bose–Einstein condensates. So I was ...
3
votes
0answers
55 views

How can we see that there is superconductivity/superfluidity in the boundary theory in the holographic principle?

For example in the models for holographic superconductors we can calculate the conductivity. Also there is an energy gap. I can understand that it describes a superconductor. However I have also heard ...
1
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1answer
82 views

Is a falling, perfect sheet of fluid possible to create?

This is a bit of an abstract question so I'll try explain this as best I can from the bottom up. I would like to know if it is possible to observe a sheet of fluid, much like a sheet of glass, ...
6
votes
0answers
73 views

What is a superfluid in field theoretic terms?

I'm wondering how one precisely defines a superfluid in terms of the effective field theory description. In Nicolis's paper http://arxiv.org/abs/1108.2513 there seems to be an extremely simple ...
1
vote
1answer
65 views

Lev Landau's proof of molecular motion at absolute zero?

I am reading the book "The man they wouldn't let die" by Alexander Dorozynski, which is an biography of Russian theoretical physicist Lev Landau, and I have encountered this passage Absolute zero ...
13
votes
3answers
225 views

Would an airplane flying through superfluid helium experience lift and drag?

Would an airplane flying through superfluid helium experience lift and drag? The airplane is presumed cold enough to not heat up the helium.
2
votes
2answers
127 views

Can a solid object float on a frictionless liquid?

Assuming the solid is less dense than the liquid, will a solid object float on a frictionless liquid? I can imagine that due to the pressure gradient the object will float, but I can also imagine ...
2
votes
1answer
165 views

Intuitive explanation for superfluidity?

I know that superfluidity is caused by the fluid having zero viscosity. This only happens at very low temperature, so the fluid (e.g. Helium-4) is a Bose-Einstein condensate. I also know that in a ...
3
votes
1answer
139 views

Simple & intuitive explanation of superfluidity?

I know that superfluidity is caused by the fluid having zero viscosity. This only happens at very low temperature, so the fluid (e.g. Helium-4) is a Bose-Einstein condensate. I also know that in a ...
1
vote
0answers
39 views

How Does The Macroscopic Wavefunction Build Up?

How does the macroscopic wavefunction (the order parameter) builds up from zero value to the a finite value when liquid He undergoes a transition from normal to the superfluid state? How does it ...
0
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0answers
14 views

Applications non-Newtonian fluid [duplicate]

Are non-Newtonian fluid difused in the "real world"? Which are most common or fantastic applications?
0
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0answers
16 views

relating the AB transition temperature in a superfluid with different coherence lengths

i have two sets of data. one leads to a value for the transition temperature from the A phase superlfuid to B phase. This was performed in a thin slab, which was too thin to observe the A-B ...
1
vote
0answers
60 views

Nomenclature clarification concerning solitons

My experience with solitons is restricted to the classical setting, namely solutions to the quartic interaction $\phi^4$, the Sine-Gordon equation, and Korteweg–de Vries equations. I was explicit to ...
10
votes
1answer
590 views

Do we have magnetic monopole? Is charge, according to yesterdays paper on Nature by Ray-Roukokoski-Kandel-Möttönen-Hall (30.01.14) quantized?

As everybody here knows, Maxwell's equation would look more beautiful if a magnetig charge were present. Beyond the aesthetics question, if a single magnetic Dirac monopole would be found, the ...
0
votes
1answer
135 views

How to calculate fluid(oil / hydrocarbon) loss under pressure

I'm trying to calculate the amount of fluid that would flow through an area dependant on the amount of pressure that there is. I'd also like to know the rate at which it would flow. Essentially I ...
0
votes
0answers
10 views

Refractive Index of Super Critical Fluids

I'm studying optics at the moment and I am wondering how the refractive index changes when a liquid is in super critical state? Thank you.
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0answers
62 views

Noether's theorem in the realm of superfluids

In 1969 Keith Moffat showed helicity conservation for ideal fluids such as liquid Helium. This work is proving seminal in our understanding of turbulent flows and viscous fluids. In the case where ...
4
votes
0answers
100 views

Third-order topological quantum phase transition in p+ip superfluid

A two-dimensional spinless non-relativistic p+ip superfluid undergoes a quantum phase transition between the BCS (weakly-coupled) and BEC (strongly-coupled) regimes. This transition is driven by ...
1
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2answers
65 views

Bulk modulus of Liquid helium and first sound

Does anyone know where to find the bulk modulus of liquid helium ? I've been looking all over the internet but everywhere I get N/A. Any tips ? I'd need it to estimate the speed of first sound in ...
0
votes
1answer
120 views

Superfluid Fountain

I was wondering how a super fluid fountain can flow indefinitely without violating energy conservation.
3
votes
1answer
900 views

What is off-diagonal long range order in superfluid?

From Wikipedia: [...]Off-diagonal long-range order (ODLRO) [...] exists whenever there is a macroscopically large factored component (eigenvalue) in a reduced density matrix of any order. How to ...
1
vote
1answer
68 views

Testing the speed of gravitational waves in superfluids

Ok. Light can be slowed down in superfluids. I would like to know whether if a Cavendish like experiment could be possible within inside superfluids i.e, to rotate two balls such that to observe their ...
3
votes
1answer
221 views

Symmetry breaking in Bose-Hubbard model

According to Landau's symmetry breaking theory, there is a symmetry breaking when phase transition occurs. What is the symmetry breaking of superfluid-Mott insulator transition in Bose-Hubbard ...
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vote
2answers
128 views

Microscopic Theory of superfluidity

In comparison with superconductivity what is the microscopic theory of superfluidity? Who has done it?
4
votes
2answers
195 views

Superfluidity and superconductivity?

Superfluidity and superconductivity? Is there any relation between the two aside from the fact that they are somewhat analogies , I see a lot of people on the internet who claim the helium (in it's ...
2
votes
1answer
212 views

periodic boundary conditions for vortex in a square lattice

I am trying to follow this paper and track the dynamics of vortex motion on a discrete (square) lattice. The idea is to simulate the time evolution of the Gross-Pitaevskii (GP) equation, which reads ...
12
votes
2answers
398 views

How to understand the emergent special relativity in the superfluid?

The superfluid vacuum theory was proposed to understand some features of the vacuum (aether) from the emergence point of view. Although made up of non-relativistic atoms, the low-energy excitations of ...
20
votes
4answers
824 views

What observables are indicative of BCS Cooper pair condensation?

What observables are indicative of BCS Cooper pair condensation? "Thought" experiments and "numerical" experiments are allowed. This question is motivated by the question Has BCS Cooper pair ...
1
vote
1answer
286 views

Can anyone explain what a superleak is?

In the context of Helium can anyone explain what a superleak is and why it could be useful?
1
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1answer
965 views

The bizarre behaviour of superfluids! Climbing up walls and geting out of glass beakers

SUPERFLUIDITY: Superfluidity is one of the most amazing quantum phenomena, which we can sit and watch them happening before our eyes! Watch this video, it is only a couple of minutes long, which ...
4
votes
2answers
211 views

Why aren't all quantum systems superfluids

Simply I was just wandering why aren't all quantum systems (F-D and BE condensates) superfluids at low temp like He 3 and 4?
9
votes
1answer
163 views

Why is the BCS trial function valid across the BEC-BCS crossover?

In one of the two main theoretical approaches used in describing ultracold Fermi gases and the BEC-BCS crossover, the so-called BCS-Leggett approach, the starting point is the BCS trial wavefunction: ...
3
votes
0answers
86 views

Two-fluid description of superfluidity

I'm trying to teach myself about superfluidity and I'm slightly confused on the ''two-fluid'' description. From what I understand, the superfluid is considered to be a mixture of two fluids, a ...
2
votes
1answer
84 views

Limits of superfluidity

Superconductivity has limits of currents and magnetic fields they can endure before dropping the superconductivity phase What are the corresponding limits of superfluidity? what are the limit ...
4
votes
1answer
888 views

Looking for a complete review of the BEC-BCS crossover

I'm looking for comprehensive review of the BEC-BCS crossover, both from a theoretical point of view, and from a experimental one. Even something at textbook level, but exhaustive, would be OK, but I ...
10
votes
3answers
432 views

What does the term liquid mean in condensed matter physics?

In condensed matter physics, people always say quantum liquid or spin liquid. What does liquid mean?
3
votes
2answers
958 views

Why water is not superfluid?

My question is in the title. I do not really understand why water is not a superfluid. Maybe I make a mistake but the fact that water is not suprfluid comes from the fact that the elementary ...
4
votes
1answer
763 views

Are all bose-einstein condensates superfluid?

I feel like the answer should be "no" since all superfluids are not strictly BEC since they can undergo a Kosterlitz–Thouless transition in 2D, for example. I believe the ideal gas isn't superfluid, ...
4
votes
1answer
428 views

Helium-4 superfluidity and gauge symmetry breaking

Is there an accessible account of superfluidity in Helium-4 as a manifestation of "global gauge symmetry" breaking? And what is meant by "global gauge symmetry"? I was taught that gauge symmetries ...
7
votes
3answers
65 views

Cosmic background radiation vs superfluids

I've been reading a lot about superfluids lately (fluids that are cooled to such a degree that they no longer obey the standard laws of physics) in various physics journals and realized that the ...
2
votes
1answer
303 views

Complex valued energy

I'm working on a 2D He superfluid system with vortices. I was asked to calculate the kinetic energy of vortex-(anti-)vortex pairs and compare the two situations. One finds in literature that the ...
3
votes
1answer
595 views

Phonons, rotons, and maxons

What are phonons, rotons, and maxons, and what does their dispersion curve have to do with superfluidity? I understand that they are quasiparticles, but I'm not entirely sure what that implies. Are ...