Ортада сигнал тарату қасиеттерін сипаттаушы тензор

Tensor characterizing signal carrying properties in a medium

In acoustics and fluid dynamics, an acoustic metric (also known as a sonic metric) is a metric that describes the signal carrying properties of a given particulate medium. (Generally, in mathematical physics, a metric describes the arrangement of relative distances within a surface or volume, usually measured by signals passing through the region – essentially describing the intrinsic geometry of the region.)

An acoustic metric can give rise to "acoustic horizons" (also known as "sonic horizons"), analogous to the event horizons in the spacetime metric of general relativity. However, unlike the spacetime metric, in which the invariant speed is the absolute upper limit on the propagation of all causal effects, the invariant speed in an acoustic metric is not the upper limit on propagation speeds. For example, the speed of sound is less than the speed of light. As a result, the horizons in acoustic metrics are not perfectly analogous to those associated with the spacetime metric. It is possible for certain physical effects to propagate back across an acoustic horizon. Such propagation is sometimes considered to be analogous to Hawking radiation, although the latter arises from quantum field effects in curved spacetime.

Since acoustic metrics share some statistical behaviours with the way that we expect a future theory of quantum gravity to behave (such as Hawking radiation), these metrics have sometimes been studied in the hope that they might shed light on the statistical mechanics of actual black holes. Some people have suggested that analog models are more than just an analogy and that the actual gravity that we observe is actually an analog theory. But in order for this to hold, since a generic analog model depends upon both the acoustic metric and the underlying background geometry, the low energy large wavelength limit of the theory has to decouple from the background geometry.