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Low temperature structural and superfluid properties of $^4$He confined in cylindrical nanopores are theoretically investigated by means of first principle Quantum Monte Carlo (QMC) simulations. We vary the density of $^4$He inside the…
We report hot-wire measurements performed in two very different, co- and counter-rotating flows, in normal and superfluid helium at 1.6 K, 2 K, and 2.3 K. As recently reported, the power spectrum of the hot-wire signal in superfluid flows…
The elementary excitations in superfluid liquid He-4 named rotons have an unusual dispersion curve. The energy is an approximately quadratic function of (p-p_0), the difference between the magnitude of the momentum p and a characteristic…
A formula for potential U of the He-4--He-4 interaction in the liquid state is obtained by the direct electromagnetic computation as a function of the interatomic distance R. The potential decreases exponentially at large R. The further…
Like many quantum fluids, superfluid helium-4 (He II) can be considered as a mixture of two miscible fluid components: an inviscid superfluid and a viscous normal fluid consisting of thermal quasiparticles [1]. A mutual friction between the…
We obtain the von K\'arm\'an-Howarth relation for the stochastically forced three-dimensional Hall-Vinen-Bekharvich-Khalatnikov (3D HVBK) model of superfluid turbulence in Helium ($^4$He) by using the generating-functional approach. We…
Using general local conservations laws we derive dispersion relations for edge modes in a slab of electron liquid confined by a symmetric potential. The dispersion relations are exact up to $\lambda^{2} q^{2}$, where $q$ is a wave vector…
The theory of sound propagation in macroscopically isotropic and homogeneous porous media saturated with superfluid ^4He(so-called He II) has been developed neglecting all damping processes. The case when the normal fluid component is…
We review our study of critical phenomena in superfluid $^4$He confined in nanoporous glasses. $^4$He in nanoporous media is an ideal ground to survey the quantum phase transition of bosons. In the present work, critical phenomena were…
A study by computer simulation is reported of the behaviour of a quantized vortex line at a very low temperature when there is continuous excitation of low-frequency Kelvin waves. There is no dissipation except by phonon radiation at a very…
The property of superfluidity, first discovered in liquid 4He, is closely related to Bose-Einstein condensation (BEC) of interacting bosons. However, even at zero temperature, when one would expect the whole bosonic quantum liquid to become…
The onset mechanism of superfluidity is examined by taking the case of the capillary flow of liquid helium 4. In the capillary flow, a substantial fall of the shear viscosity has been observed in the normal phase (lambda point<T<3.7K). In…
The relationship between the apparently unrelated physical quantities -- kinematic viscosity of liquid He-4, $\nu$, and quantum of circulation, $\kappa=2\pi \hbar/m_4$, where $\hbar$ is the Planck constant and $m_4$ denotes the mass of the…
We measure the response of a rotating sample of superfluid $^3$He-B to spin-down to rest in the zero-temperature limit. Deviations from perfect cylindrical symmetry in the flow environment cause the initial response to become turbulent. The…
We have measured the interaction between superfluid $^3$He-B and a micro-machined goalpost-shaped device at temperatures below $0.2\,T_c$. The measured damping follows well the theory developed for vibrating wires, in which the Andreev…
Based on the many-boson system structure factor, which takes into account three- and four-particle direct correlations, there was found the first sound velocity temperature behaviour in liquid $^4$He in the post-RPA approximation. The…
The hybridization of the single-excitation branch with the two-excitation continuum in the momentum region beyond the roton minimum is reconsidered by including the effect of the interference term between one and two excitations. Fits to…
Recently, it has been argued by Kuklov et al., that unusual features associated with the superflow-through-solid effect observed in solid He4 can be explained by unique properties of dilute distribution of superfluid edge dislocations. We…
We measure the oscillations of a standing wave of phonons in a Bose-Einstein condensate, thus obtaining the dispersion relation. We present the technique of short Bragg pulses, which stimulates the standing wave. The subsequent oscillations…
We show that there can exist two liquid states in distinguishable helium-4 ($^4$He) obeying Boltzmann statistics by path integral centroid molecular dynamics (CMD) simulations. This is an indication of quantum liquid polyamorphism induced…