Questions tagged [superfluidity]
A flow with no viscosity
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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 ...
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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 ...
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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 ...
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15 views
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. ...
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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 ...
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1answer
42 views
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 ...
2
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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 ...
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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 $T_c$ ...
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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 ...
3
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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 $.
(...
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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 ...
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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 ...
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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 ...
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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 ...
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1answer
61 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:
$$\rho=\hat{z}\cdot(\partial_x\vec{v}\times \partial_y\vec{v})$$
$$j^x=\hat{z}\cdot(...
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29 views
Topological properties of dark solitons in superfluid systems
In the study of superfluid systems, vortices are often referred to as "topological excitations", because the winding of the phase of the superfluid order parameter around a vortex is a topological ...
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1answer
50 views
Resource request: Superfluid helium
I am wondering if anybody could recommend any good textbooks on the subject. So far, I have discovered (but not yet had a chance to read), a chapter in Landau-Lifshitz fluid mechanics (love Landau-...
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1answer
56 views
Superfluidity: separation of quantised vortices in a vortex tangle
It is often quoted (see https://doi.org/10.1016/j.piutam.2013.09.008) that the separation $\delta$ between quantised vortices in a vortex tangle in a superfluid is approximately
$$\delta \approx L^{-...
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36 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}...
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1answer
120 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 ...
2
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1answer
86 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 ...
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1answer
78 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 ...
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0answers
48 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-...
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0answers
54 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 ...
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1answer
120 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 ...
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1answer
240 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 ...
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0answers
155 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 ...
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1answer
52 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, ...
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0answers
172 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 ...
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1answer
227 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 + \...
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2answers
189 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
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 ...
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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 ...
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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 ...
4
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 $h_{c2}$, ...
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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 ...
