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A colleague asked me this question and I had no clue.

When a function (for instance, a sine wave) is multiplied by a decaying exponential, we call the phenomenon damping. What would it be called if the wave is multiplied by a growing exponential?

I suggested forcing or driving, since functions of that form arise in simple harmonic oscillators driven by sine waves with frequency equal to the oscillator's frequency. But I wondered if others had words for it.

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"Negative damping" or "positive feedback" are common. –  Arturo Magidin Apr 27 '11 at 17:13
Driven/driving is certainly the term I've heard; see here for example. –  Zev Chonoles Apr 27 '11 at 17:15
Exciting comes to mind. –  Emre Apr 27 '11 at 17:20
Ramping? ...... –  mjqxxxx Apr 27 '11 at 19:24
People (at least in electrical engineering) use amplification (=gain) as the opposite of damping (=loss)... –  Fabian Apr 27 '11 at 20:13

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