Critical fluctuations and slowing down of chaos

Fluids cooled to the liquid–vapor critical point develop system-spanning fluctuations in density that transform their visual appearance. Despite a rich phenomenology, however, there is not currently an explanation of the mechanical instability in the molecular motion at this critical point. Here, we...

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Bibliographic Details
Published in:Nature communications 2019-05, Vol.10 (1), p.2155-2155, Article 2155
Main Authors: Das, Moupriya, Green, Jason R.
Format: Article
Language:English
Subjects:
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639/638/563/981
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Approximation
Chain dynamics
Computational fluid dynamics
Computer simulation
Critical phenomena
Critical point
Dynamical systems
Exponents
Fluctuations
Fluids
Humanities and Social Sciences
Initial conditions
Mathematical models
Molecular motion
Motion stability
multidisciplinary
Nonlinear dynamics
Nonlinear systems
Phenomenology
Science
Science (multidisciplinary)
Simulation
Statistical physics
Statistics
Vapors
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Summary:Fluids cooled to the liquid–vapor critical point develop system-spanning fluctuations in density that transform their visual appearance. Despite a rich phenomenology, however, there is not currently an explanation of the mechanical instability in the molecular motion at this critical point. Here, we couple techniques from nonlinear dynamics and statistical physics to analyze the emergence of this singular state. Numerical simulations and analytical models show how the ordering mechanisms of critical dynamics are measurable through the hierarchy of spatiotemporal Lyapunov vectors. A subset of unstable vectors soften near the critical point, with a marked suppression in their characteristic exponents that reflects a weakened sensitivity to initial conditions. Finite-time fluctuations in these exponents exhibit sharply peaked dynamical timescales and power law signatures of the critical dynamics. Collectively, these results are symptomatic of a critical slowing down of chaos that sits at the root of our statistical understanding of the liquid–vapor critical point. It is well known that fluids become opaque at the liquid–vapor critical point, but a description of the underlying mechanical instability is still missing. Das and Green leverage nonlinear dynamics to quantify the role of chaos in the emergence of this critical phenomenon.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-019-10040-3