Comment on “Collective modes and gapped momentum states in liquid Ga: Experiment, theory, and simulation”

Bryk, Taras; Mryglod, I. M.; Ruocco, G.

doi:10.1103/physrevb.103.096301

Cited by 4 publications

(2 citation statements)

References 18 publications

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“…On the contrary, the Frenkel time seems to attain to the dynamics of the single liquid molecule which is definitely not the character in discussion here since hydrodynamics refers only to the long-wavelength collective dynamics. These points have been already discussed in the literature [92][93][94]. Recently Ref.…”

Section: A Theoretical Backgroundmentioning

confidence: 64%

Deformations, relaxation, and broken symmetries in liquids, solids, and glasses: A unified topological field theory

2022

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We combine hydrodynamic and field theoretic methods to develop a general theory of phonons as Goldstone bosons in crystals, glasses, and liquids based on nonaffine displacements and the consequent Goldstone phase relaxation. We relate the conservation, or lack thereof, of specific higher-form currents with properties of the underlying deformation field-nonaffinity-which dictates how molecules move under an applied stress or deformation. In particular, the single-valuedness of the deformation field is associated with conservation of higher-form charges that count the number of topological defects. Our formalism predicts, from first principles, the presence of propagating shear waves above a critical wave vector in liquids, thus giving a formal derivation of the phenomenon in terms of fundamental symmetries. The same picture provides also a theoretical explanation of the corresponding "positive sound dispersion" phenomenon for longitudinal sound. Importantly, accordingly to our theory, the main collective relaxation timescale of a liquid or a glass (known as the α relaxation for the latter) is given by the phase relaxation time, which is not necessarily related to the Maxwell time. Finally, we build a nonequilibrium effective action using the in-in formalism defined on the Schwinger-Keldysh contour, that further supports the emerging picture. In summary, our work suggests that the fundamental difference between solids, fluids, and glasses has to be identified with the associated generalized higher-form global symmetries and their topological structure, and that the Burgers vector for the displacement fields serves as a suitable topological order parameter distinguishing the solid (ordered) phase and the amorphous ones (fluids, glasses).

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Section: A Theoretical Backgroundmentioning

confidence: 64%

Deformations, relaxation, and broken symmetries in liquids, solids, and glasses: A unified topological field theory

2022

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“…which is fundamental for all liquids [5][6][7][8]. Recently some of us [10] have demonstrated that one obtains results, which contradict the known dynamic properties of liquids, if the continuity equation is not taken into account. As a consequence of the absence of the continuity equation (5) in their treatment, BLZ claim that their longitudinal sound would come "from the mixing of energy fluctuations and longitudinal momentum fluctuations" (quoting BLZ [1]), at variance with textbook knowledge [5][6][7][8].…”

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confidence: 99%

Comment on "Deformations, relaxation and broken symmetries in liquids, solids and glasses: a unified topological field theory"

Bryk,

Schirmacher,

Ruocco

2022

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We discuss a field-theoretical approach to liquids, solids and glasses, published recently [Phys.Rev.E 105, 034108 (2022)], which aims to describe these materials in a common quantum formalism. We argue that such quantum formalism is not applicable to classical liquids, and the results presented, which rely heavily on the concept of phase relaxation borrowed from quantum fluids, contradict the known hydrodynamic theory of classical liquids. In particular, the authors miss the important particle-number conservation law and the density fluctuations as hydrodynamic slow variable. Instead, the authors invoke Goldstone bosons as elementary hydrodynamic excitations. We point out that in a classical liquid there are no broken continuous symmetries and consequently no Goldstone bosons. The authors claim that the Goldstone bosons would be responsible for the existence of sound in liquids, instead of resulting from combined particle-number and momentum conservation, a fact well documented in fluid-mechanics textbooks.

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Erratum: Collective modes and gapped momentum states in liquid Ga: Experiment, theory, and simulation [Phys. Rev. B 101 , 214312 (2020)]

Khusnutdinoff¹,

Cockrell²,

Dicks³

et al. 2021

Phys. Rev. B

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Comment on “Collective modes and gapped momentum states in liquid Ga: Experiment, theory, and simulation”

Cited by 4 publications

References 18 publications

Deformations, relaxation, and broken symmetries in liquids, solids, and glasses: A unified topological field theory

Deformations, relaxation, and broken symmetries in liquids, solids, and glasses: A unified topological field theory

Comment on "Deformations, relaxation and broken symmetries in liquids, solids and glasses: a unified topological field theory"

Erratum: Collective modes and gapped momentum states in liquid Ga: Experiment, theory, and simulation [Phys. Rev. B 101 , 214312 (2020)]

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