Physics

Fluids thicken at the speed of light: new theory extends Einstein’s theory of relativity to real fluids

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Special relativity has many surprising and counterintuitive effects, the most famous of which are length reduction and time dilation. If an object moves with a velocity relative to an observer that is a non-negligible fraction of the speed of light, the length of the object in the direction of movement will appear to the observer to be shorter than its actual length. Remaining frame.

In particular, only the coefficient equal to the value divided by the Lorentz coefficient is displayed shorter. The latter depends only on the relative velocity between the object and the observer and the speed of light, and can only be greater than or equal to 1, resulting in a “length contraction” effect.

Length contraction and time dilation are well-established relativistic effects, known even before Einstein’s 1905 paper on special relativity, but others regarding other fundamental physical properties One may wonder whether the relativistic effects of can also be predicted by special relativity.

For example, despite intense research in the field of relativistic fluid mechanics, there is so far no relativistic theory of fluid viscosity that can also recover the classical gas limit. Not yet. This is a clear sign that the available relativistic theories of viscosity are probably incomplete.

In a new article published in Physical Review E, I present a non-linear analysis of microscopic particles based on the recently proposed relativistic Langevin equation (derived from a relativistic microscopic particle bath Lagrangian). We derived a general microscopic theory of fluid viscosity, combined with affine theory. -Level displacement under flow. This framework describes the microscopic movement of particles (atoms or ions) as a result of interactions and collisions with other particles under forced flow fields.

Particles tend to follow the flow field, but they can also deviate from the flow field due to interactions with other particles. These “deviations” are called “non-affine” motions and contribute significantly to the dissipation of momentum of the moving fluid.

In special relativity, the “momentum” associated with the relative motion of an object to an observer is the “proper momentum” which is the particle’s normal momentum multiplied by the Lorentz factor (again, the latter is a number). It is always greater than 1 and can be very large for objects moving at or near the speed of light).

The new theory I came up with is that the viscosity of a fluid that is proportional to the loss of proper momentum of a fluid moving at speeds close to the speed of light is proportional to the normal viscosity of the same fluid moving at normal speeds multiplied by It shows that. Lorentz factor.

When I checked whether my microscopic relativistic theory could recover the classical gas viscosity known from kinetic theory and many aerodynamic experiments in the non-relativistic limit of low speeds. , I was very surprised. In fact, it turns out that the new formula is able to recover the correct dependence of viscosity on temperature, particle mass and size, and Boltzmann’s constant, known for classical gases (such as air flowing near the wings of an airplane). .

In the opposite limit for energetic fluids moving at extremely high speeds (such as quark-gluon plasmas and classical relativistic plasmas), the theory predicts a cubic dependence on temperature, consistent with the evidence, and Create a new set of fundamental physical laws. The most important fundamental constant in nature.

Interestingly, I realized that the new theory could reveal the hitherto ignored influence of Einstein’s theory of relativity. For example, in analogy with length contraction and time dilation, “fluid thickening” can be talked about as a new relativistic effect that has hitherto been overlooked, and is a relative phenomenon in astrophysics and high-energy physics. This could have important implications for our understanding of theoretical plasmas. , including quark-gluon plasmas obtained from high-energy nuclear collision reactions.

This story is part of the Science X Dialog, where researchers can report findings from published research papers. To learn more about Science X Dialog and how to participate, visit this page.

Further information: Alessio Zaccone, Relativistic theory of fluid viscosity across the energy spectrum, Physical Review E (2024). DOI: 10.1103/PhysRevE.110.L052101. For arXiv: DOI: 10.48550/arxiv.2406.18434

Biography: Alessio Zaccone received his Ph.D. He received his PhD from the Department of Chemistry, ETH Zurich in 2010. From 2010 to 2014, he was an Oppenheimer Fellow at the Cavendish Laboratory, University of Cambridge. Since 2022, he has been Full Professor and Professor of Theoretical Physics at the Department of Physics at the University of Milan, after having served on the faculty at the Technical University of Munich (2014-2015) and the University of Cambridge (2015-2018). These include the ETH Silver Medal, the 2020 Gauss Professorship at the Göttingen Academy of Sciences, the Cambridge Queen’s College Fellowship, and the ERC Consolidator Grant (‘Multimech’).

Research contributions include analytical solutions for jamming transition problems (Zaccone & Scossa-Romano PRB 2011), analytical solutions for random close-packed problems in two and three dimensions (Zaccone PRL 2022), and thermally activated reaction kinetics. Includes process theory. Shear flow (Zaccone et al. PRE 2009), theory of crystal nucleation under shear flow (Mura & Zaccone PRE 2016), theoretical prediction of boson-like peaks in vibrational spectra of crystals (Milkus & Zaccone PRB 2016; Baggioli & Zaccone PRL 2019), glass transition theory in polymers (Zaccone & Terentjev PRL 2013), theoretical and computational discovery of topological defects in glasses (Baggioli, Kriuchevskyi, Sirk, Zaccon PRL 2021), and theoretical predictions of superconductivity enhancement by phonon decay. Effect (Setty, Bagioli, Zaccon PRB 2020). Research interests range from statistical physics of disordered systems (random packing, jamming, glasses and glass transitions, colloids, non-equilibrium thermodynamics) to solid state physics and superconductivity.

Citation: Fluids thicken at the speed of light: New theory extends Einstein’s theory of relativity to real fluids (November 7, 2024) https://phys.org/news/2024-11-fluids- thicken- Theory- Retrieved November 10, 2024 from Einstein-Real.html

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