The spectral shape and intensity of the optical signals from the N-V centers are sensitive to external perturbation.
Suppose now that some time , an external perturbation is applied to the system, driving it out of equilibrium.
It is also possible for widely separated binaries to lose gravitational contact with each other during their lifetime, as a result of external perturbations.
The balance-flow model gives no clue on the initial speed of an inertial circle, which needs to be triggered by some external perturbation.
These two techniques allow the atoms or ions to be highly isolated from external perturbations, thus producing an extremely stable frequency reference.
In addition, there are constant external perturbations, such as breezes, and internal perturbations that come from respiration.
In condensed matter physics, relaxation is usually studied as a linear response to a small external perturbation.
Due to an external perturbation, a standing capillary wave can form at the liquid-air interface.
In 2D correlation analysis, a sample is subjected to an external perturbation while all other parameters of the system are kept at the same value.
Because a rocket, propellant and exhaust in flight, without any external perturbations, may be considered as a closed system, the total momentum is always constant.