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The Lumenary

Practice · Advanced undergraduate

Dynamical systems and chaos

Dynamical systems and chaos

Warm-upHuman

The map f(x)=x3f(x) = x^3 has three fixed points. How many of them are attracting?

Dynamical systems and chaos

Warm-upHuman

Classify the equilibrium at the origin of x˙=x+2y\dot x = x + 2y, y˙=3x+2y\dot y = 3x + 2y.

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Dynamical systems and chaos

CoreHuman

For the logistic map with r=2.5r = 2.5, how do orbits starting near the fixed point x∗=1−1/r=0.6x^* = 1 - 1/r = 0.6 behave?

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Dynamical systems and chaos

CoreHuman

How many points of the circle have minimal period exactly 33 under the doubling map D(x)=2x mod 1D(x) = 2x \bmod 1?

Dynamical systems and chaos

CoreHuman

On the torus R2/Z2\R^2/\Z^2, the flow x˙=1\dot x = 1, y˙=2\dot y = \sqrt2 has no equilibria, every orbit is bounded, and every orbit is dense — so no orbit is periodic or approaches a periodic orbit. Which hypothesis of the Poincaré–Bendixson theorem fails?

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Dynamical systems and chaos

CoreFormal

In Mathlib, which statement says that p lies on an orbit of f of period exactly 2 (periodic with period 2, but not a fixed point)?

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Dynamical systems and chaos

CoreHuman

Consider x˙=−y−x(x2+y2)\dot x = -y - x(x^2 + y^2), y˙=x−y(x2+y2)\dot y = x - y(x^2 + y^2). Which statement about the origin is correct?

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Dynamical systems and chaos

CoreComputational

Write lyapunov(r, x0, n, transient) that estimates the Lyapunov exponent of the logistic map fr(x)=rx(1−x)f_r(x) = rx(1 - x): iterate transient times from x0 without recording, then return the average of ln⁡∣fr′(xk)∣=ln⁡∣r(1−2xk)∣\ln|f_r'(x_k)| = \ln|r(1 - 2x_k)| over the next n iterates xkx_k.

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Dynamical systems and chaos

StretchHuman

Which statements are true? Choose all that apply.

Choose all that apply

Dynamical systems and chaos

StretchHuman

For which values of rr is the period-2 orbit {p+,p−}\{p_+, p_-\} of the logistic map attracting?

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