Article
Mechanics
Aditya G. G. Nair, James Hanna, Matteo Aureli
Summary: In two-dimensional decaying homogeneous isotropic turbulence, kinetic energy and enstrophy are transferred to larger and smaller scales, respectively. It is challenging to identify the important flow structures that govern this behavior in such complex dynamics. Two flow-modification strategies are proposed and implemented, leveraging the inviscid global conservation of energy and enstrophy to selectively and simultaneously change these quantities and guide the system towards steady-state or late-stage behavior. One strategy is based on local flow field information, while the other is global. Various flow structures excited by these modified inputs are observed and compared with recent literature. Energy modification excites smaller wavenumber structures in the flow, while enstrophy modification differs.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Multidisciplinary
Ildoo Kim
Summary: The study successfully characterized turbulent soap film flows using entropy analysis, revealing the anisotropy of turbulence and the increase in the most unpredictable time scale with downstream distance, indicating decaying turbulence.
Article
Materials Science, Multidisciplinary
Jing-Ren Zhou, Qing-Rui Wang, Zheng-Cheng Gu
Summary: This paper studies fermionic topological phases with q-type anyon excitations and generalizes the construction by Gu, Wang, and Wen. By using a set of nonlinear algebraic equations and constraints on phase factors, we are able to construct a topological invariant partition for 3D spin manifolds.
Article
Mechanics
Yan Yang, Minping Wan, William H. Matthaeus, Shiyi Chen
Summary: In studies of compressible magnetohydrodynamic (MHD) turbulence, it was found that compressive kinetic and thermal energy exchange is driven by acoustic waves through pressure dilatation, while exchange between kinetic and magnetic energy is dominated by interactions involving solenoidal velocity. Systematic rapid adjustments were found to be reproducible with simple scalings derived from empirical data.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Brodie C. Pearson, Jenna L. Pearson, Baylor Fox-Kemper
Summary: The study proposes new relations to diagnose energy and enstrophy dissipation rates in anisotropic two-dimensional turbulence, using second-order advective structure functions. These new relations show improvement over existing methods through increased accuracy, insensitivity to sampling direction, and lower temporal and spatial variability. Advective structure functions have benefits under weakly anisotropic conditions, becoming increasingly important as third-order structure functions become inappropriate.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Astronomy & Astrophysics
Pallavi Bhat, Muni Zhou, Nuno F. Loureiro
Summary: Recent numerical studies have shown the existence of inverse transfer of magnetic energy in 3D magnetically dominated turbulence, likely driven by magnetic reconnection. The scaling behavior is found to be similar between 2D and 3D cases. Furthermore, simulations also demonstrate an inverse transfer of magnetic energy in 3D when the magnetic field is subdominant to the flow, with the emergence of a dynamo effect.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Optics
Thudiyangal Mithun, Kenichi Kasamatsu, Bishwajyoti Dey, Panayotis G. Kevrekidis
Summary: The study investigates quantum turbulence in miscible binary Bose-Einstein condensates and the formation of vortex-antidark structures under certain conditions. The interplay of parameter asymmetry and trap frequencies affects the dynamics of turbulent condensates, leading to the emergence of unique spectral features related to incompressible kinetic energy. Additionally, the impact of intercomponent interaction on like-signed vortex cluster formation in an elliptical steep-wall trap is examined, revealing the decay of clustered configurations due to intercomponent coupling.
Article
Mechanics
Jin-Han Xie, Shi-Di Huang
Summary: Through simulations of an idealized isotropic convection system, we provide evidence for the existence of Bolgiano-Obukhov (BO) scaling in Rayleigh-Benard convection (RBC) and establish its association with the inverse kinetic energy cascade. We also observe strong intermittent effects in the buoyancy field, but not in the velocity.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Multidisciplinary
Leonardo Campanelli
Summary: This research constructs a discrete shell model for two-dimensional turbulence that incorporates local and nonlocal interactions between velocity modes in Fourier space. The continuous limit of this model in real space is described by the one-dimensional Burgers equation. The study finds a novel approximate scaling solution for this equation and demonstrates its ability to accurately describe the main characteristics of the energy spectrum in fully developed, freely decaying two-dimensional turbulence.
JOURNAL OF THE KOREAN PHYSICAL SOCIETY
(2022)
Article
Physics, Multidisciplinary
Adam Griffin, Giorgio Krstulovic, Victor S. L'vov, Sergey Nazarenko
Summary: We present an exact unique constant-flux power-law analytical solution for the wave kinetic equation, applicable for ak << 1. Our theory describes acoustic turbulence in 2D Bose-Einstein condensates, and the corresponding spectrum is confirmed through numerical simulations.
PHYSICAL REVIEW LETTERS
(2022)
Article
Mechanics
Nikolay A. Ivchenko, Sergey S. Vergeles
Summary: The study focuses on time-averaged properties of coherent vortices in two-dimensional turbulence, classifying weak perturbations as waves of condensate propagating in the radial direction. The dispersion law and propagation length of these waves are dependent on the radial position inside the vortex flow, with variations between saturated condensate and viscous condensate cases.
Article
Materials Science, Multidisciplinary
Zhu -Xi Luo
Summary: This article discusses the stacking of a gapped boundary of a (3+1)D topological order (TO) with a decoupled (2+1)D TO to obtain another boundary theory. The author argues that different classes of gapped boundaries of (3+1)D TO should be defined modulo the decoupled (2+1)D TOs. Furthermore, the possibility of coupling the boundary of a (3+1)D TO to additional (2+1)D TOs or fractonic systems is examined, leading to more possibilities for gapped boundaries. The classification of gapped boundaries based on stringlike excitations is proposed.
Article
Mechanics
Xander M. de Wit, Adrian van Kan, Alexandros Alexakis
Summary: In this study, direct numerical simulations of thin-layer flow were used to investigate whether the bistable range survives as the domain size and turbulence intensity are increased. The research found that the bistable range grows as the box size and/or Reynolds number Re are increased.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Martin Jacques-Coper, Valentina Ortiz-Guzman, Jorge Zanelli
Summary: This study presents a simplified model of the terrestrial planet atmosphere, describing it as a two-dimensional open system with an ideal gas. The model considers the effects of radiation, matter exchange, diffusion, and dissipation. The dynamics of the atmosphere is governed by non-linear differential equations, and the problem can be solved analytically or numerically depending on the level of non-linearity. The study provides analytical expressions and simulations for the linear regime, allowing exploration of the model's response to parameter changes. Interestingly, a 2.5% reduction in emissivity can lead to a 7-degree Celsius increase in average global temperature.
Article
Physics, Multidisciplinary
Murad Abuzarli, Nicolas Cherroret, Tom Bienaime, Quentin Glorieux
Summary: We report on the observation of a prethermal state in a nonequilibrium, two-dimensional fluid of light. By directly measuring the first order coherence function of the fluid, we observe the emergence of algebraic correlations, which resemble the properties of thermal superfluids. Increasing the fluctuations leads to a transition from algebraic to short-range correlations. This phenomenon is interpreted as a nonequilibrium precursor of the Kosterlitz-Thouless transition.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Applied
M. M. Cawte, M. T. Reeves, A. S. Bradley
Summary: In this study, quantum vortex states consisting of a ring of vortices with alternating sign in a homogeneous superfluid were investigated. An exact stationary solution for the neutral vortex necklace was found. The stability of the necklace state within both the point-vortex model and the Gross-Pitaevskii equation was examined, revealing sensitivity to perturbations and potential for vortex chaos or quantum turbulence.
JOURNAL OF LOW TEMPERATURE PHYSICS
(2021)
Article
Optics
M. D. E. Denys, M. K. Olsen, L. S. Trainor, H. G. L. Schwefel, A. S. Bradley
Summary: The study analyzes the degenerate intracavity triplet down conversion process using quantum phase-space techniques, finding that quantum effects are most pronounced in the region immediately above the semi-classical pumping threshold. Through simulating time evolution, steady states, and calculating fluctuation spectra, regimes of squeezing, bipartite entanglement, and non-Gaussianity can be observed in the cavity output fields.
OPTICS COMMUNICATIONS
(2021)
Article
Physics, Multidisciplinary
Matthew T. Reeves, Kwan Goddard-Lee, Guillaume Gauthier, Oliver R. Stockdale, Hayder Salman, Timothy Edmonds, Xiaoquan Yu, Ashton S. Bradley, Mark Baker, Halina Rubinsztein-Dunlop, Matthew J. Davis, Tyler W. Neely
Summary: We experimentally study the emergence of microcanonical equilibrium states in the turbulent relaxation dynamics of a two-dimensional chiral vortex gas. The resulting long-time vortex distributions are in excellent agreement with the mean-field Poisson Boltzmann equation for the system, and a point-vortex model with phenomenological damping and noise can quantitatively reproduce the equilibration dynamics.
Article
Physics, Multidisciplinary
Zain Mehdi, Ashton S. Bradley, Joseph J. Hope, Stuart S. Szigeti
Summary: This theoretical investigation focuses on the stochastic decay of persistent currents in a toroidal ultra cold atomic superfluid, caused by a perturbing barrier. The study utilizes detailed three-dimensional simulations to model an experiment, observing a strong temperature dependence in the timescale of superflow decay. Results of the simulations show quantitative discrepancies at higher temperatures, suggesting the need for further experimental and theoretical studies on superflow stability.
Article
Physics, Multidisciplinary
Callum L. Grimshaw, Thomas P. Billam, Simon A. Gardiner
Summary: This article investigates a scheme for interferometric measurement using bright solitons in atomic Bose-Einstein condensates. The scheme uses the geometric scalar potential experienced by atoms in a spatially dependent dark state to overcome the limitation of barrier width in interferometric measurement. Numerical simulations are conducted to probe the effects of deviations from the ideal configuration.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Thomas P. Billam, Kate Brown, Ian G. Moss
Summary: Cold atomic gases can simulate the physics of the early Universe in the laboratory, with features similar to high energy particle theory. This paper describes a three-level system that undergoes a first-order phase transition through bubble nucleation. Theoretical investigation shows bubbles nucleating in two dimensions at non-zero temperature. The bubble nucleation rates calculated from a stochastic projected Gross-Pitaevskii equation and a non-perturbative instanton method show good agreement. Bubbles preferentially nucleate near the walls of the trap when an optical box trap is included in the simulations.
NEW JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
Zain Mehdi, Joseph J. Hope, Stuart S. Szigeti, Ashton S. Bradley
Summary: We present a microscopic open quantum systems theory for the thermally damped vortex motion in oblate atomic superfluids. The theory considers previously neglected energy-damping interactions between superfluid and thermal atoms. The mechanism strongly couples to vortex core motion, leading to the dissipation of vortex energy and the Brownian motion of vortices. We derive an analytic expression for the dimensionless mutual friction coefficient that agrees well with experimentally measured values.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Optics
Ashton S. Bradley, Jordan Clarke, Tyler W. Neely, Brian P. Anderson
Summary: In this study, we propose an exact reformulation of the Gross-Pitaevskii equation for ultracold Bose gas, which allows simulations of long evolution times during expansion or similar large-scale manipulation by using a coordinate frame that adaptively scales with the system size. Our approach does not make hydrodynamic approximations and is not limited to specific assumptions or potentials. We apply our method to simulate various scenarios including the expansion of an ideal gas, a cigar-shaped condensate in the Thomas-Fermi regime, and a linear superposition of counterpropagating Gaussian wave packets. We identify different scaling regimes and show that there is no exact, aspect-ratio invariant, free expansion for nonlinear evolution.
Article
Optics
Ashton S. Bradley, R. Kishor Kumar, Sukla Pal, Xiaoquan Yu
Summary: The study of turbulent flows requires the consideration of excitations on different length scales. In this paper, we develop a spectral analysis method for quantum fluids with U(1) symmetry-breaking, which can be used to analyze turbulent flows. Our method takes into account the quantum phase information and allows for arbitrary resolution spectral analysis, providing a rigorous tool for analyzing quantum features of superfluid turbulence.
Article
Optics
Kali E. Wilson, E. Carlo Samson, Zachary L. Newman, Brian P. Anderson
Summary: We demonstrate a method to generate multiply quantized superfluid circulation in highly oblate Bose-Einstein condensates (BECs) through experimental and numerical approaches. By spiraling a blue-detuned laser beam around and towards the center of the BEC, we are able to achieve pinned superflow with high winding numbers. This method can be used to generate persistent currents or control the placement of clusters of singly quantized vortices with the same circulation.
Article
Optics
Thomas P. Billam, Kate Brown, Ian G. Moss
Summary: This study proposes an ultracold atom analog of false-vacuum decay using all three states of a spin-1 Bose gas, avoiding instabilities caused by time-modulated coupling, and examines the dependence of vacuum decay rate on particle density for 7Li and 41K with reasonable agreement with instanton methods.
Article
Optics
Thomas P. Billam, Kate Brown, Andrew J. Groszek, Ian G. Moss
Summary: The study analyzes the supercooled state in an analog of an early universe phase transition using a one-dimensional, two-component Bose gas with time-dependent interactions. It shows that the system behaves similarly to a thermal, relativistic Bose gas undergoing a first-order phase transition. The study proposes a method to prepare the system in a metastable phase and reveals that parametric resonances can be suppressed by thermal damping.
Article
Physics, Multidisciplinary
Kali E. Wilson, Alexander Guttridge, I-Kang Liu, Jack Segal, Thomas P. Billam, Nick G. Parker, N. P. Proukakis, Simon L. Cornish
Summary: In this study, we investigate the collective dynamics of a quantum degenerate Bose-Bose mixture of Cs-133 and Yb-174 with attractive interspecies interactions. The experiments and numerical simulations reveal complex and interesting behaviors, such as significant damping of the Cs dipole mode and the possibility of late-time revivals highly sensitive to Cs and Yb atom number combinations. Additionally, we explore the stability of the degenerate mixture and observe collapse of the Cs condensate mediated by the attractive Cs-Yb interaction under certain conditions, in good agreement with simulations.
PHYSICAL REVIEW RESEARCH
(2021)