What's the minimum (physics first) to get an oscillator?

[jonpaul]

Simple answer:
Loop gain > 1

Works for any osc, mechanical, electric, electronic.



Jon

[SiliconWizard]

Everything is an oscillator.

[The Electrician]

There was a lady on the Coast to Coast radio show: https://en.wikipedia.org/wiki/Coast_to_Coast_AM

the other night who informed the listeners that everything in the universe has a frequency.  There must be a lot of oscillators keeping it all going.

[AndyBeez]

Is white noise oscillation?

[TimFox]

No, it is "variation".
Inherent in the term "oscillation", starting with the physics of harmonic oscillators and the engineering of feedback oscillators is that the action be periodic.

[AK6DN]

Two requirements for an oscillator:
1) a feedback loop
2) gain greater than unity

[TimFox]

Two requirements for an oscillator:
1) a feedback loop
2) gain greater than unity

The title of this post is "what's the minimum (physics first) to get an oscillator?" (emphasis supplied)
As I keep pointing out, in physics an "oscillator" does not have to produce a sustained output, as does a feedback oscillator in engineering.
Even in engineering, there are non-feedback oscillators (such as negative-resistance or relaxation oscillators).

[metebalci]

From a mathematical and physics point of view, you need to have a second order time derivative in the differential equation that describes the system. This is the only way the solution will include a complex exponential which will involve functions of sin() and cos().

Interesting thread.

The quote above is too restrictive though. There are higher order DEs which can be proven to oscillate, though I'm not at all familiar with the methods (and as you note later, coupled first order DEs like Lotka-Volterra can also oscillate - do we count them as "really" second order?) - there is a branch of DE maths called oscillation theory which treats these problems.

Lotka-Volterra is second order, isnt it ? Why "really" ? There is a pair of first order equations.

I think an oscillation can happen in one dimensional discrete systems but for a continuous one two dimensions are needed (not possible to have two unstable points next to each in one dimension I think?)