Example · Undergraduate

Terms

TermThis exampleWhy
periodic orbit ✓ The unit circle is a periodic orbit of the harmonic oscillator, because the solution $(\cos t, -\sin t)$ goes around the unit circle with period $2 \pi$.
omega limit set ✓ The unit circle is the ω-limit set of each of its own points, because the solutions on it go around it periodically.
limit cycle ✗ The unit circle is not a limit cycle of the harmonic oscillator, because every nearby circle is also a periodic orbit, so it is not isolated.
attractive ✗ The unit circle is not attractive for the harmonic oscillator, because nearby solutions stay on their own circles and do not approach it.
attractor ✗ The unit circle is not an attractor for the harmonic oscillator, because nearby solutions do not approach it.

Distinctions using this example

  • Periodic orbit vs. limit cycle: The unit circle is a periodic orbit of the harmonic oscillator but not a limit cycle, because every circle around the origin is also a periodic orbit, so the unit circle is surrounded by other periodic orbits.

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