Quasinormal Mode
Quasinormal modes (QNM) are the modes of energy dissipation of a perturbed object or field, i.e. they describe perturbations of a field that decay in time. A familiar example is the perturbation (gentle tap) of a wine glass with a knife: the glass begins to ring, it rings with a set, or superposition, of its natural frequencies -- its modes of sonic energy dissipation. One could call these modes normal if the glass went on ringing forever. Here the amplitude of oscillation decays in time, so we call its modes quasi-normal. To a very high degree of accuracy, quasinormal ringing can be approximated by
where is the amplitude of oscillation, is the frequency, and is the decay rate. The quasinormal frequency is described by two numbers,
or, more compactly
where stands for the real part. Here, is what is commonly referred to as the quasinormal mode frequency. It is a complex number with two pieces of information: real part is the temporal oscillation; imaginary part is the temporal, exponential decay.
In certain cases the amplitude of the wave decays quickly, to follow the decay for a longer time one may plot
-
- The sound of quasinormal ringing
Read more about Quasinormal Mode: Mathematical Physics, Biophysics
Famous quotes containing the word mode:
“The mode of clearing and planting is to fell the trees, and burn once what will burn, then cut them up into suitable lengths, roll into heaps, and burn again; then, with a hoe, plant potatoes where you can come at the ground between the stumps and charred logs; for a first crop the ashes suffice for manure, and no hoeing being necessary the first year. In the fall, cut, roll, and burn again, and so on, till the land is cleared; and soon it is ready for grain, and to be laid down.”
—Henry David Thoreau (1817–1862)