# Questions tagged [superfluidity]

A flow with no viscosity

150 questions
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### Convert Normal water to cool instantly [on hold]

Is it possible to convert the hot/normal water to cold steam instantly(may be within 1/2hr) without using refrigerators etc. If yes, how far can the cold steam travel. I am not sure with all the fluid ...
2answers
68 views

### What's the difference and relationship between perfect fluid and superfluid?

Sorry for this naive question, I just cannot find good references talking about the difference and relationship between perfect fluid and superfluid. Could someone explain this to me or point me to ...
0answers
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### Is the streaming of a superliquid through a circular tube equivalent to the current running in a circular piece of superconducting material?

When a superfluid streams endlessly through an isolated circular tube is the same mechanism at work as in the endless current moving through an isolated circular piece of superconducting material? Is ...
0answers
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### How will a rotating, circular, and cylindrical body of a superfluid develop in outer space?

Let's consider a rotating (about its center, in the plane cutting the initial circular and cylindrical form into two halves), circular, and cylindrical body of a superfluid somewhere in outer space. ...
0answers
27 views

### Do Goldstone modes with linear dispersion always correspond to superfluidity?

For a superfluid, we get that the Goldstone modes has a linear dispersion. $\omega=vk$ where $v$ will be a critical velocity. We can have no excitations caused by impurities with a velocity less that ...
1answer
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### Why we can't write low energy effective field theory for a gapless system?

Assume that we have an Hamiltonian $$H=H_0+H_{int}$$ where $H_0$ has gappless excitations and $H_{int}$ has usual two body interactions. If $H_0$ were gapped I would able to get low energy effective ...
0answers
52 views

### Energy dissipation from a black hole by neutrinos

Could the high gravitation field of a black hole cause neutrinos to form a Fermi gas or superfluid? Could these neutrinos from the neutrino background of the big bang whose temperature and deBroglie ...
1answer
524 views

### What is so topological about topological phase transitions?

I am studying the KT-transition, which is called a topological phase transition. The phase transition is driven by vortices in a 2-D superfluid, where it is shown that at a critical temperature $T_c$ ...
0answers
35 views

### What if an ocean planet is covered by superfluid ocean? [closed]

It is possible that an ocean planet can be covered by superfluid state liquid. What will happens on this kind of planet? Will there be any changes to tide? Will there be strong magnetic field? Will ...
1answer
62 views

### BCS theory for neutral fermions

As I understand it, Cooper pairs form between two fermions and are the cause of superconductivity. I was told by a teacher that the formation of Cooper pairs and BCS theory requires both fermions to ...
0answers
22 views

### What would happen if we test the Hagen-Poiseuille law with a superfluid?

When we have a laminar flow we can test the Hagen-Poiseuille law from the pressure difference created by the flow of the fluid. This process is created due to conservation of total energy but the ...
1answer
95 views

### Does (Tomas) Bohr's modified double slit argument really doom Couder's quantum/classical fluid dynamics analogy?

I'm just an amateur, probably why I find the de Broglie/Bohm/Couder approach to QM compelling. But Copenhagen struck back: in a coincidence, Bohr's grandson is a fluid physicist who claims that ...
1answer
25 views

### How do we imagine the transition between phonons and rotons?

In the theory of superfluidity, we have both phonon and roton excitations. Phonons are long-range density fluctuations (sound waves) and rotons are short-range (atomic scale) circulations of the atoms ...
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86 views

### What macroscopic fields exist around color supercurrent?

For an ordinary superconductor such as Lead, charge supercurrent gives rise to a magnetic field around the whole material for low enough currents. At large enough currents, the superconductor will ...
1answer
41 views

### What is *diagonal* long range order?

I have seen this question about off-diagonal long range order in superfluids. What’s the difference and the significance between long range diagonal and off-diagonal long range order?
0answers
35 views

### What is the link between superfluids and BEC?

i’m studying superfluids (in particular $^4 He$) and one of the first theorical apporoach was with Bose-Einstein condensation and i know that we can calculate the $T_c$ and it is close to the the ...
1answer
109 views

### Vortex in superfluid?

I'm studying superfluid helium 4. I have studied that the superfluid has a velocity : $\vec{v}_s = \frac{\hbar}{m} \vec{\nabla} \varphi(\vec{r})$ $\rightarrow$ $\nabla \times \vec{v}_s = 0$. (...
2answers
87 views

### vortex anti-vortex configuration to ground state [closed]

i'm studying kosterlitz transition. I'm reading this: https://assets.nobelprize.org/uploads/2018/06/advanced-physicsprize2016-1.pdf?_ga=2.51324009.1302372948.1538119052-1605759177.1538119052 Now ...
1answer
238 views

### Is dark matter a superfluid?

The fact that the dark matter halos surrounding colliding galactic clusters simply pass through each other without interacting has a simple explanation. If they are superfluid bodies, wouldn't be ...
0answers
18 views

### Why the form factors on the green function of relativistic two-component liquid model for superfluid have this form?

I am working in trying to understand Appendix A of arXiv:0906.4810. On this appendix, the authors set up an external velocity field perturbating a superfluid, described by a two-component model. This ...
1answer
115 views

### Holographic Superfluid Space Time and Temperature

I am approaching this from a layman’s perspective and curious about what those more expert in the field have to say about my understanding of Superfluid vacuum theory and the holographic principle and ...
1answer
61 views

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2answers
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### Is density fluctuation gapless in superfluid?

Deep in the superfluid phase, the superfluid order parameter $\phi$ can be decomposed into the amplitude (density) mode $\rho$ and the phase mode $\theta$ as $$\phi=\sqrt{\rho} e^{\mathrm{i}\theta}.$$ ...
0answers
60 views

### Introductory condensed matter physics book [duplicate]

I need a book for general condensed matter physics, preferably at an undergraduate level, e.g. at Ashcroft and Mermin's level or below. Modern applications are preferred.
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126 views

### Superconductivity and superfluidity in bosonic and fermionic condensates

Can bosonic and fermionic condensates explain superfluid and superconducting properties? Are they better than the theory of BCS and Landau? Edited: My question is based in this lecture pesentation ...
2answers
61 views

### Is there a phase coexistence line below the critical temperature $T_c$ in normal to superfluid transition?

In the case of water, there is a phase coexistence line (called the liquid-gas coexistence curve) which ends in a critical point. And this line separates the gas phase from the liquid phase in the P-T ...
1answer
206 views

### Why do pairing and condensation occur simultaneously in superconductors?

Bose condensation in the weak-coupling limit (such as BCS superconductors) and the strong-coupling limit (like BECs of atoms) can be unified into a single framework by the BEC-BCS crossover. One key ...
1answer
208 views

### Are there Goldstone bosons in the spontaneous normal to superfluid transition?

The normal to the superfluid transition of liquid helium breaks is a U(1) global symmetry. Since it is a continuous, global symmetry (unlike superconductivity which is a gauge theory), I expect that ...
0answers
142 views

### The appearance of a gapless phase mode in Landau Ginzburg theory of charged superconductor

My question is simply: Why do the Landau Ginzburg(LG) theory of superconductors describe a phase mode which is ungapped/massless when it should be promoted to the plasma frequency? I will try to ...
0answers
238 views

### Sod shock tube - Contact Discontinuity

sorry for bothering with my question. https://en.wikipedia.org/wiki/Sod_shock_tube I have trying to understand, how is it possible to have a discontinuity on Density and not on Pressure. I don't ...
2answers
62 views

### Quantification of the circulation in superfluids : why does the phase jump by $2 \pi$?

In superfluidity we have the current density that is $j=\frac{h}{m} \vec{\nabla}(\phi)$ Where the wavefunction describing the system is : $\psi(\vec r)=\sqrt{n_s}e^{i \phi(\vec{r})}$ We then ...
1answer
43 views

### How superfluidity can arise at extremely high temperatures

I'm a mathematicians and I don't have a big knowledge of physics. I've heard that superfluidity can arise inside a neutron star and I've given to understand that this has to do with a hugh density ...
2answers
90 views

### The two-current model of superconductivity

Standard text books (Landau and Lifshitz etc) explain that the correct macroscopic theory of a superfluid is two-fluid hydrodynamics. A superfluid is made of two components, a viscous normal fluid and ...
1answer
321 views

### Why are superfluid vortex lattices stable?

Both (a) neutral superfluids that are externally rotated, and (b) type-II superconductors (i.e. charged superfluids) under applied magnetic fields between the critical fields $h_{c1}$ and $h_{c2}$, ...
1answer
770 views

### What causes liquid helium to climb walls?

It is a phenomenon which can be observed if your search on the web. Apparently liquid Helium can crawl up through walls. Does every superfluid do this crawling action or is it just special for liquid ...