Wave-formed ripple Wave-formed ripple In sedimentology, wave-formed ripples or wave-formed ripple marks are a feature of sediments (sandstones, limestones, siltstones) and dunes. These ripple marks are often characterised (and thus distinguished from current ripples) by symmetric cross sections and long relatively straight crests, which may commonly bifurcate. Commonly, these crests can be truncated by subsequent flows. Their wavelength (periodicity) depends on the sediment grain size, water depth and water-particle orbits in the waves. On tidal flats the pattern of wave-formed ripples may be complicated, as a product of changing depth and wind and tidal runoff directions. Symmetrical ripples are commonly found in
Zero sound transport equation is valid in the regime where formula_36 and formula_37. In many systems, formula_38 only slowly depends on the angle between formula_39 and formula_40. If formula_29 is an angle-independent constant formula_42 with formula_43 (note that this constraint is stricter than the Pomeranchuk instability) then the wave has the form formula_44 and dispersion relation formula_45 where formula_46 is the ratio of zero sound phase velocity to Fermi velocity. If the first two Legendre components of the Landau parameter are significant, formula_47 and formula_48, the system also admits an asymmetric zero sound wave solution formula_49 (where formula_50 and formula_51 are the