342 research outputs found
Propagation of thermal excitations in a cluster of vortices in superfluid 3He-B
We describe the first measurement on Andreev scattering of thermal
excitations from a vortex configuration with known density, spatial extent, and
orientations in 3He-B superfluid. The heat flow from a blackbody radiator in
equilibrium rotation at constant angular velocity is measured with two quartz
tuning fork oscillators. One oscillator creates a controllable density of
excitations at 0.2Tc base temperature and the other records the thermal
response. The results are compared to numerical calculations of ballistic
propagation of thermal quasiparticles through a cluster of rectilinear
vortices.Comment: 6 pages, 4 figure
The State of the Art in Hydrodynamic Turbulence: Past Successes and Future Challenges
We present a personal view of the state of the art in turbulence research. We
summarize first the main achievements in the recent past, and then point ahead
to the main challenges that remain for experimental and theoretical efforts.Comment: 19 pages, 6 figures, submitted to Physica
Dynamical Equilibration Across a Quenched Phase Transition in a Trapped Quantum Gas
The formation of an equilibrium quantum state from an uncorrelated thermal
one through the dynamical crossing of a phase transition is a central question
of non-equilibrium many-body physics. During such crossing, the system breaks
its symmetry by establishing numerous uncorrelated regions separated by
spontaneously-generated defects, whose emergence obeys a universal scaling law
with the quench duration. Much less is known about the ensuing re-equilibrating
or "coarse-graining" stage, which is governed by the evolution and interactions
of such defects under system-specific and external constraints. In this work we
perform a detailed numerical characterization of the entire non-equilibrium
process, addressing subtle issues in condensate growth dynamics and
demonstrating the quench-induced decoupling of number and coherence growth
during the re-equilibration process. Our unique visualizations not only
reproduce experimental measurements in the relevant regimes, but also provide
valuable information in currently experimentally-inaccessible regimes.Comment: Supplementary Movie Previes: SM-Movie-1: https://youtu.be/3q7-CvuBylg
SM-Movie-2: https://youtu.be/-Gymaiv9rC0 SM-Movie-3:
https://youtu.be/w-O2SPiw3nE SM-Movie-4: https://youtu.be/P4xGyr4dwK
Density Functional Theory of doped superfluid liquid helium and nanodroplets
During the last decade, density function theory (DFT) in its static and
dynamic time dependent forms, has emerged as a powerful tool to describe the
structure and dynamics of doped liquid helium and droplets. In this review, we
summarize the activity carried out in this field within the DFT framework since
the publication of the previous review article on this subject [M. Barranco et
al., J. Low Temp. Phys. 142, 1 (2006)]. Furthermore, a comprehensive
presentation of the actual implementations of helium DFT is given, which have
not been discussed in the individual articles or are scattered in the existing
literature. This is an Accepted Manuscript of an article published on August 2,
2017 by Taylor & Francis Group in Int. Rev. Phys. Chem. 36, 621 (2017),
available online: http://dx.doi.org/10.1080/0144235X.2017.1351672Comment: 113 pages, 42 figure
In situ imaging of vortices in Bose-Einstein condensates
Laboratory observations of vortex dynamics in Bose-Einstein condensates
(BECs) are essential for determination of many aspects of superfluid dynamics
in these systems. We present a novel application of dark-field imaging that
enables \texttt{\it in situ} detection of two-dimensional vortex distributions
in single-component BECs, a step towards real-time measurements of complex
two-dimensional vortex dynamics within a single BEC. By rotating a Rb
BEC in a magnetic trap, we generate a triangular lattice of vortex cores in the
BEC, with core diameters on the order of 400 nm and cores separated by
approximately 9 m. We have experimentally confirmed that the positions of
the vortex cores can be determined without the need for ballistic expansion of
the BEC.Comment: 5 pages, 4 figure
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