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Collocation quadrature data are well defined
Statement
For the distinct nodes and cardinal polynomials in Collocation tableau from distinct quadrature nodes, every entry of , every component of , and the Lebesgue constant is a finite real number.
Facts & Assumptions
Given: An integer and distinct nodes as in Collocation tableau from distinct quadrature nodes.
Cardinal-polynomial interpolation and Cardinal interpolation functions are polynomials of the stated degrees: each cardinal function is a polynomial of degree at most .
Sums, scalar multiples, products, absolute values, maxima, minima and quotients with nonvanishing denominator of continuous functions are continuous, as are constants, the identity and every polynomial function: polynomial functions, absolute values of continuous functions, and finite sums of continuous functions are continuous.
A continuous function on is Riemann integrable, by Heine-Cantor and Riemann's criterion: a continuous real function on a nondegenerate compact interval is Riemann integrable. For a degenerate interval, The integral with oriented limits: and stipulates that the integral is zero.
Intervals of : the nine order-convex forms, nondegeneracy, and length and Lower bound, bounded below, bounded set: is closed and bounded. A subset of is compact if and only if it is closed and bounded makes it compact, so Extreme value theorem: a continuous real function on a nonempty compact subset of attains a greatest and a least value gives a finite maximum of the continuous cardinal sum.
Proof
By [F1], each is a polynomial, hence continuous by [F2]. For every , its restriction to is Riemann integrable by [F3] when , and its integral is when . Its integral on is also finite by [F3]. Thus all defining entries and are finite.
The function is continuous by [F2]; [F4] supplies its finite maximum on . This is exactly from the definition. The matrices and the vector have finitely many finite entries, so their displayed finite sums and row norms are finite as well.
Depends on
- Collocation tableau from distinct quadrature nodes
- Cardinal-polynomial interpolation
- Cardinal interpolation functions are polynomials of the stated degrees
- A continuous function on $[a,b]$ is Riemann integrable, by Heine-Cantor and Riemann's criterion
- Sums, scalar multiples, products, absolute values, maxima, minima and quotients with nonvanishing denominator of continuous functions are continuous, as are constants, the identity and every polynomial function
- Extreme value theorem: a continuous real function on a nonempty compact subset of $\mathbb{R}$ attains a greatest and a least value
- The integral with oriented limits: $\int_a^a f := 0$ and $\int_b^a f := -\int_a^b f$
- A subset of $\mathbb{R}$ is compact if and only if it is closed and bounded
- Intervals of $\mathbb{R}$: the nine order-convex forms, nondegeneracy, and length
- Lower bound, bounded below, bounded set
Used by
- Finite explicit-left-Euler spectral deferred-correction sweep Algorithm
- Two-node Gauss collocation gives the exact endpoint for a nonstiff cubic IVP Example
- A Gaussian collocation defect has a high-order weighted endpoint bound Lemma
- M-node collocation has local defect order M Theorem
- M-node Gauss collocation has local defect order 2M Theorem
- Small-step collocation maps are Lipschitz stable Theorem
Cited to discharge well-definedness by Collocation tableau from distinct quadrature nodes.
Dependency tree · two levels
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Sources
- Ernst Hairer, Syvert P. Nørsett, and Gerhard Wanner, Solving Ordinary Differential Equations I, 2nd ed., Chapter II §II.7 (standard reference, not scraped)