Questions tagged [superfluidity]
A flow with no viscosity
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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 ...
3
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1answer
52 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 ...
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15 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 ...
2
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1answer
54 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 ...
1
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1answer
20 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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0answers
81 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 ...
0
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1answer
30 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?
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0answers
28 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 ...
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1answer
96 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 $.
(...
1
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2answers
67 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 ...
0
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1answer
223 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 ...
1
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0answers
17 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 ...
2
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1answer
73 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 ...
1
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1answer
56 views
A conservation law in fluid dynamics
Let's consider a water flow in two dimensional space, assume the velocity field is $\vec{v}(t,x,y)$, we can define:
$$\rho=\hat{z}\cdot(\partial_x\vec{v}\times \partial_y\vec{v})$$
$$j^x=\hat{z}\cdot(...
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0answers
26 views
flowing water with really high Reynolds number hitting a wall not prependicular
A streamline of water is incident upon a wall at an angle $\theta$ where $\theta \neq 90°$ Friction can be neglected.
What will the force exerted on the point of incidence be?
If we assume the flow ...
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0answers
29 views
Topological properties of dark solitons in superfluid systems
In the study of superfluid systems, vortices are often referred to as "topological excitations", because the winding of the phase of the superfluid order parameter around a vortex is a topological ...
0
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1answer
43 views
Resource request: Superfluid helium
I am wondering if anybody could recommend any good textbooks on the subject. So far, I have discovered (but not yet had a chance to read), a chapter in Landau-Lifshitz fluid mechanics (love Landau-...
2
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1answer
50 views
Superfluidity: separation of quantised vortices in a vortex tangle
It is often quoted (see https://doi.org/10.1016/j.piutam.2013.09.008) that the separation $\delta$ between quantised vortices in a vortex tangle in a superfluid is approximately
$$\delta \approx L^{-...
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0answers
32 views
The correct expression for pressure, temperature in Landau's 2-fluid model
Setup: the system of equations
I would like to numerically solve the equations of motion in Landau's [Ref (1)] two-fluid description of superfluid He II, which are
$$
\frac{\partial \rho}{\partial t}...
2
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1answer
102 views
Is the superfluid state a coherent state?
In the normal to a superfluid phase transition, U(1) symmetry related to particle number conservation is spontaneously broken which seems to imply that the superfluid state is a state in which there ...
0
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0answers
141 views
Whats the speed of sound in the superfluid vacuum?
In the superfluid vacuum theory, sound can propagate in the vacuum, as it is connected to vacuum energy considerations.
Quote: "There are several theories of a superfluid vacuum. These theories have ...
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0answers
31 views
Superfluids: what is the physics that predicts how thick is a Rollin film?
I do not have much familiarity with the physics of fluids (or superfluids, by the way) and I couldn't find what physically makes a Rollin film to be as thin as it is (I know that the order of ...
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1answer
47 views
Is the $\lambda$ point in superfluid helium understood?
When liquid helium is cooled below a certain temperature, it undergoes a second phase transition from He I to He II. The specific heat spikes at the famous lambda point. Is this spike in the specific ...
0
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0answers
96 views
Does Helium really stay a liquid at $0K$ due to zero-point motion?
People often say that helium stays a liquid at low temperatures due to "zero point motion.'' I decided to test this for myself. Based on this source which estimates that the depth of the potential ...
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0answers
50 views
Superfluidity in one dimension?
Why is there no superfluidity in one dimension? What is the connection to higher dimensional superfluidity, static/thermodynamical, and dynamical responses?
0
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1answer
58 views
Why do rotons correspond to the minimum of the dispersion curve?
The dispersion curve for superfluid helium-4 is given above. To my knowledge, the first paper that was able to argue that the curve should take this shape from first principles was Feynman's 1954 ...
2
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0answers
34 views
Definition of Superfluid with no Bose-Einstein condensation?
A BEC with no superfluidity is referred to as Bose Glass (due to S. Yukalov to my knowledge). Is anyone aware of a similar definition for systems which exhibit superfluid behaviour but are not Bose-...
2
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0answers
47 views
Observational evidence for superfluidity in neutron stars
What is the earliest evidence for the existence of superfluidity in neutron stars?
I'm about to present the subject in a seminar and I'm under the impression that at the moment there is no ...
1
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1answer
98 views
Quasiclassical propagator
Sometimes they are referred as Keldysh quasiclassical propagator or Eilenberger propagator. How the quasiclassical propagator is derived? How they are implement with a simple case of a Green's ...
1
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1answer
191 views
Landau critical velocity and sound velocity
The definition of Landau critical velocity is
$v_L=\min_{q}\{\frac{\omega(q)}{q}\}$, where $\omega(q)$ is the spectrum of excitations. The viscosity vanishes when the object is moving through the ...
3
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0answers
125 views
Superfluidity book recommendation
I'm preparing for a senior undergrad seminar on superfluidity and quantized vortices, and my professor seems to prefer old textbooks, so I wondered what modern (~90's onwards) books on these phenomena ...
0
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1answer
39 views
Energy of the excitation in the superfluid
According to the chapter 1.3: Superfluidity, from the book "Methods of Quantum Field Theory In Statistical Physics by A.A Abrikosov, it is written that
Consider a Bose liquid at absolute zero, ...
2
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0answers
166 views
Is gapless spectrum necessary for superfluity
In 3D interacting Boson system, the condensate leads to a gapless spectrum and superfluidity. The same gapless spectrum for 2D with quasi-condensate (correct me if it is wrong ).
I am wondering if it ...
1
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1answer
172 views
Partition function of weakly interacting Bose gas
In the Bogoliuobov theory of superfluidity, the hamiltonian of a system of weakly interacting bosons in second quantized notation is diagonalized with the following result:
$$\hat H = H_0 \hat1 + \...
6
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2answers
169 views
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
$$\phi=\sqrt{\rho} e^{\mathrm{i}\theta}.$$
...
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0answers
50 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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0answers
101 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 ...
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0answers
62 views
Effect of electromagnetic field on atoms of supercooled helium in a vacuum
I'm trying to predict what would happen to supercooled helium atoms in a vacuum when a strong electromagnetic field was present nearby. I think that a Lorentz force would move the helium atoms away ...
1
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2answers
56 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 ...
4
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1answer
184 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 ...
4
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1answer
165 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 ...
2
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0answers
118 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 ...
0
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0answers
57 views
The single valuedness of the superfluid and superconductor order parameter
For a superfluid, why does the phase of the order-parameter must be single valued? Does the answer differ for a superconductor? Does the answer depends on the topology of the manifold?
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0answers
202 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 ...
0
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2answers
58 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 ...
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1answer
42 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 ...
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2answers
83 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 ...
11
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1answer
267 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 $h_{c2}$, ...
3
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1answer
589 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 ...
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1answer
73 views
Why do superfluid vortices form a lattice?
I often hear that in a superfluid, vortices get arranged in a lattice but I don't understand why and I've been hard pressed to find a discussion of it online.
I'm aware that vortices should repel ...
