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Design of optimal Runge-Kutta methods - FEniCS Project

Design of optimal Runge-Kutta methods - FEniCS Project

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The Stability Function<br />

For the linear equation<br />

u ′ = λu,<br />

a <strong>Runge</strong>-<strong>Kutta</strong> method yields a solution<br />

u n+1 = φ(λ∆t)u n ,<br />

where φ is called the stability function <strong>of</strong> the method:<br />

Example: Euler’s Method<br />

φ(z) = det(I − z(A − ebT )<br />

det(I − zA)<br />

u n+1 = u n + ∆tF (u); φ(z) = 1 + z.<br />

D. Ketcheson (KAUST) 10 / 36

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