Acoustic analogies with general relativity, quantum fields, and thermodynamics

Abstract: Modern physics is based on three major theories - general relativity, quantum field theory, and (quantum) thermodynamics. Classical acoustics in fluids is usually regarded and studied as a part of classical mechanics, more precisely fluid dynamics. This assumes velocities much below the speed of light and length scales much above the molecular scale. However, like acoustics, all three modern theories are field theories, whether classical (gravitation) or quantum (quantum field theory and quantum thermodynamics). This fact opens possibilities for establishing direct analogies between acoustics and the other theories, which are in the focus of the work presented here. The analogy with covariant (as well as quantum) vector theory of electromagnetism is also addressed, as the most natural link between the analogue scalar theory of acoustics and the second-order tensor theory of general relativity. All these allow an analogue unified theory to be defined, in which the fundamentals of classical acoustics in fluids are expressed using the formalisms of modern field theories, and which should further help narrowing the gap between the apparently remote physics.