721 research outputs found
Scale Separation Scheme for Simulating Superfluid Turbulence: Kelvin-Wave Cascade
A Kolmogorov-type cascade of Kelvin waves--the distortion waves on vortex
lines--plays a key part in the relaxation of superfluid turbulence at low
temperatures. We propose an efficient numeric scheme for simulating the Kelvin
wave cascade on a single vortex line. The idea is likely to be generalizable
for a full-scale simulation of different regimes of superfluid turbulence. With
the new scheme, we are able to unambiguously resolve the cascade spectrum
exponent, and thus to settle the controversy between recent simulations [1] and
recently developed analytic theory [2].
[1] W.F. Vinen, M. Tsubota and A. Mitani, Phys. Rev. Lett. 91, 135301 (2003).
[2] E.V. Kozik and B.V. Svistunov, Phys. Rev. Lett. 92, 035301 (2004).Comment: 4 pages, RevTe
Optical scattering angles and Bose-stimulated motion in cold atomic gas
Bose statistics imply a substantial enhancement at small angles for light
scattering off a cold, Bose gas. The enhancement increases dramatically at the
Bose-Einstein temperature. This phenomenon could be utilized to eliminate
almost entirely the heating of the gas by a weak probe light beam.Comment: 9 pages (REVTeX) and 1 figure (ps); revisions: some new comments
relevant to current experiments and one math typo; to appear in Physics
Letters
Comment on ``Hausdorff Dimension of Critical Fluctuations in Abelian Gauge Theories"
Hove, Mo, and Sudbo [Phys. Rev. Lett. 85, 2368 (2000)] derived a simple
connection, , between the anomalous scaling dimension of
the U(1) universality class order parameter and the Hausdorff dimension
of critical loops in loop representations of U(1) models. We show that the
above relation is wrong and establish a correct relation that contains a new
critical exponent.Comment: In 1 revtex page with 1 figur
Rotational response of superconductors: magneto-rotational isomorphism and rotation-induced vortex lattice
The analysis of nonclassical rotational response of superfluids and
superconductors was performed by Onsager (in 1949) \cite{Onsager} and London
(in 1950) \cite{London} and crucially advanced by Feynman (in 1955)
\cite{Feynman}. It was established that, in thermodynamic limit, neutral
superfluids rotate by forming---without any threshold---a vortex lattice. In
contrast, the rotation of superconductors at angular frequency ---supported by uniform magnetic field
due to surface currents---is of the rigid-body type (London Law). Here we show
that, neglecting the centrifugal effects, the behavior of a rotating
superconductor is identical to that of a superconductor placed in a uniform
fictitious external magnetic filed . In particular,
the isomorphism immediately implies the existence of two critical rotational
frequencies in type-2 superconductors.Comment: replaced with published versio
The 17/5 spectrum of the Kelvin-wave cascade
Direct numeric simulation of the Biot-Savart equation readily resolves the
17/5 spectrum of the Kelvin-wave cascade from the 11/3 spectrum of the
non-local (in the wavenumber space) cascade scenario by L'vov and Nazarenko.
This result is a clear-cut visualisation of the unphysical nature of the 11/3
solution, which was established earlier on the grounds of symmetry.Comment: 2 pages, 1 figur
Kolmogorov and Kelvin-Wave Cascades of Superfluid Turbulence at T=0: What is in Between?
As long as vorticity quantization remains irrelevant for the long-wave
physics, superfluid turbulence supports a regime macroscopically identical to
the Kolmogorov cascade of a normal liquid. At high enough wavenumbers, the
energy flux in the wavelength space is carried by individual Kelvin-wave
cascades on separate vortex lines. We analyze the transformation of the
Kolmogorov cascade into the Kelvin-wave cascade, revealing a chain of three
distinct intermediate cascades, supported by local-induction motion of the
vortex lines, and distinguished by specific reconnection mechanisms. The most
prominent qualitative feature predicted is unavoidable production of vortex
rings of the size of the order of inter-vortex distance.Comment: 4 RevTex pages, 1 figure. Quantitative analysis of the regime 2 has
been revise
Two-Dimensional Weakly Interacting Bose Gas in the Fluctuation Region
We study the crossover between the mean-field and critical behavior of the
two-dimensional Bose gas throughout the fluctuation region of the
Berezinskii--Kosterlitz--Thouless phase transition point. We argue that this
crossover is described by universal (for all weakly interacting |psi|^4 models)
relations between thermodynamic parameters of the system, including superfluid
and quasi-condensate densities. We establish these relations with
high-precision Monte Carlo simulations of the classical |psi|^4 model on a
lattice, and check their asymptotic forms against analytic expressions derived
on the basis of the mean-field theory.Comment: Revtex, 8 pages, 8 figures; submitted to Phys. Rev. A; extended
discussion of effective interaction and of a trapped gas; corrected typo in
Eq. (32
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