Lagrangian formulation and symmetrical description of liquid dynamics

Understand

Theoretical description of liquids has been primarily based on the hydrodynamic approach and its generalization to the solid-like regime.

• We show that the same liquid properties can be derived starting from solid-like equations and generalizing them to account for the hydrodynamic flow.
• Both approaches predict propagating shear waves with the notable gap in $k$-space.
• This gives an important symmetry of liquids regarding their description.