Quantization of Macroscopic Motions and Hydrodynamics of Rotating Helium II

Андроникашвили, Э.Л.; Mamaladze, Yu.G.

doi:10.1103/revmodphys.38.567

Cited by 135 publications

(40 citation statements)

References 65 publications

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“…(20)] and the glass temperature T 0 > 0 K, [Eq. (29)], while in our analysis we assumed for simplicity and to avoid the use of too many adjustable parameters that β = 1 and T 0 = 0 K. For more realistic glass models one would need to relax these constraints. Indeed, Fig.…”

Section: Discussionmentioning

confidence: 99%

Origin of the decrease in the torsional-oscillator period of solidHe4

et al. 2007

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A decrease in the rotational period observed in torsional oscillator measurements was recently taken as a possible indication of a putative supersolid state of helium. We reexamine this interpretation and note that the decrease in the rotation period is also consistent with a solidification of a small liquidlike component into a lowtemperature glass. Such a solidification may occur by a low-temperature quench of topological defects (e.g., grain boundaries or dislocations) which we examined in an earlier work. The low-temperature glass can account for not only a monotonic decrease in the rotation period as the temperature is lowered but also explains the peak in the dissipation occurring near the transition point. Unlike the non-classical rotational inertia scenario, which depends on the supersolid fraction, the dependence of the rotational period on external parameters, e.g., the oscillator velocity, provides an alternate interpretation of the oscillator experiments.

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Section: Discussionmentioning

confidence: 99%

Origin of the decrease in the torsional-oscillator period of solidHe4

et al. 2007

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“…(ii) In contrast to (i), superfluidity is dramatically in evidence in 4 He but, while the superfluid fraction is essentially 100% below 1 K [12], only 7% of the atoms are in a condensate. This value is arrived at both from neutron scattering experiments [13] and from Diffusion Monte Carlo calculations [14].…”

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confidence: 82%

Roton excitations in Bose–Einstein condensates and a fluid–solid transition

March

Tosi

2005

Physics and Chemistry of Liquids

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Several authors have recently discussed the existence of roton excitations in Bose-Einstein condensates (BECs) and considered how a roton dip in the dispersion curve of elementary excitations may be related to the formation of a spatially modulated ground state. Here attention is drawn to a theoretical study of Minguzzi et al. on interatomic correlations in a BEC from dipole-dipole interactions induced by laser light of increasing intensity. Attractive interactions in superfluid 4 He and repulsive interactions in 'untuned' BECs are then compared and contrasted, the experiments of Woods and Cowley and of Greiner et al. providing the focus respectively. It is stressed that, contrary to a very recent assertion by Nazario and Santiago, 4 He is crucially different from BECs at the lowest temperatures.It has been shown in the recent literature that the emergence of a roton dip in the dispersion relation of elementary excitations in a gaseous Bose-Einstein condensate (BEC) can be driven by interatomic correlations due to long-range interactions between dipoles, either permanent [1] or induced by irradiation with a far-off-resonance laser [2]. This feature in the excitation spectrum of a BEC may in turn lead to a quantum phase transition into a spatially modulated ground state [3,4]. Nazario and Santiago [5] have more recently proposed that roton excitations in a BEC may be signatures of proximity to a Mott insulating phase. Here their study is first related to previous theoretical conclusions drawn by Minguzzi et al. [3]. These authors drew on the work of O'Dell et al.[2] and interpreted the BEC structure factor S(k, I ) driven by laser intensity I as heralding a fluid-solid transition at a critical height of its main peak.

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“…The term T was not included in the original derivation of Hall & Vinen (1956a, b). It was proposed by Andronikashvili & Mamaladze (1966), to take into account the curvature of the vortex lines. The vortex tension T arises from the local circulation around a vortex line.…”

Section: Mutual Friction and Vortex Tensionmentioning

confidence: 99%

“…The mean area density of vortex lines is ω s /κ. Hence the average straightening force per unit volume of superfluid is (eω s /κ)(ω s · ∇)ω s = ρ s ν s ω s × (∇ ×ω s ), with ν s = e/(ρ s κ) (Khalatnikov 1965;Andronikashvili & Mamaladze 1966). In order to evaluate this force, we need the energy per unit length of vortex line, which is given classically by e = ρ s κ 2 ln(b 0 /a 0 )/(4π), where b 0 is the intervortex spacing and a 0 is the core radius of the vortex.…”

Section: Mutual Friction and Vortex Tensionmentioning

confidence: 99%

Superfluid spherical Couette flow

et al. 2008

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We solve numerically for the first time the two-fluid Hall-Vinen-BekarevichKhalatnikov (HVBK) equations for an He-II-like superfluid contained in a differentially rotating spherical shell, generalizing previous simulations of viscous spherical Couette flow (SCF) and superfluid Taylor-Couette flow. The simulations are conducted for Reynolds numbers in the range 1 × 10 2 6 Re 6 3 × 10 4 , rotational shear 0.1 6 Ω/Ω 6 0.3, and dimensionless gap widths 0.2 6 δ 6 0.5. The system tends towards a stationary but unsteady state, where the torque oscillates persistently, with amplitude and period determined by δ and Ω/Ω. In axisymmetric superfluid SCF, the number of meridional circulation cells multiplies as Re increases, and their shapes become more complex, especially in the superfluid component, with multiple secondary cells arising for Re > 10 3 . The torque exerted by the normal component is approximately three times greater in a superfluid with anisotropic Hall-Vinen (HV) mutual friction than in a classical viscous fluid or a superfluid with isotropic Gorter-Mellink (GM) mutual friction. HV mutual friction also tends to 'pinch' meridional circulation cells more than GM mutual friction. The boundary condition on the superfluid component, whether no slip or perfect slip, does not affect the large-scale structure of the flow appreciably, but it does alter the cores of the circulation cells, especially at lower Re. As Re increases, and after initial transients die away, the mutual friction force dominates the vortex tension, and the streamlines of the superfluid and normal fluid components increasingly resemble each other. In non-axisymmetric superfluid SCF, three-dimensional vortex structures are classified according to topological invariants. For misaligned spheres, the flow is focal throughout most of its volume, except for thread-like zones where it is strain-dominated near the equator (inviscid component) and poles (viscous component). A wedge-shaped isosurface of vorticity rotates around the equator at roughly the rotation period. For a freely precessing outer sphere, the flow is equally strain-and vorticity-dominated throughout its volume. Unstable focus/contracting points are slightly more common than stable node/saddle/saddle points in the viscous component, but not in the inviscid component. Isosurfaces of positive and negative vorticity form interlocking poloidal ribbons (viscous component) or toroidal tongues (inviscid component) which attach and detach at roughly the rotation period. 222

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Quantization of Macroscopic Motions and Hydrodynamics of Rotating Helium II

Cited by 135 publications

References 65 publications

Origin of the decrease in the torsional-oscillator period of solidHe4

Origin of the decrease in the torsional-oscillator period of solidHe4

Roton excitations in Bose–Einstein condensates and a fluid–solid transition

Superfluid spherical Couette flow

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