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4 votes

Intractability of an integral by deterministic numerical methods

For small $n$ Monte Carlo integration is not needed. For $n$ up to 100 see Kolmogorov-Smirnov Tests when Parameters are Estimated with Applications to Tests of Exponentiality and Tests on Spacings (t …
Carlo Beenakker's user avatar
40 votes
Accepted

How does Mathematica do symbolic integration?

An overview by one of the developers of Mathematica, focusing on definite integrals, is at Symbolic definite integration: methods and open issues. Mathematica knows all the entries in Gradshteyn-Ryzhi …
Carlo Beenakker's user avatar
7 votes

A numerical calculation for an integral

Nemo's representation of $F(\eta)$ in terms of a hypergeometric function can be evaluated without difficulty for large $\eta$: $$F(\eta)=\frac{\sqrt{3} {\eta}^2 \Gamma \left(\frac{2}{3}\right) \; _1F_ …
Carlo Beenakker's user avatar
4 votes

Fourier series of $e^{(\cos(\pi x) - m)^2}$

For large $s$ a single sum in terms of a hypergeometric function may be useful, $$c_{p}=\frac{(-1)^p}{2^p p!}\sum_{n=0}^\infty\frac{(n)_p}{(2s)^{n}n!}(m+1)^{n-p} {}_2F_1\bigl(p+1/2,p-n,2p+1,2/(m+1)\bi …
Carlo Beenakker's user avatar
1 vote

Approximation for a Bessel function integral

Q: The OP seeks a "reasonable approximation" for large or small $\rho_0$ of the function $$P(x)= \int_0^{x} e^{-\rho^2-\rho_0^2} \rho I_0(2\rho \rho_0)\,d\rho,\;\;x\geq 0.$$ Consider the kernel $$p …
Carlo Beenakker's user avatar
2 votes
Accepted

Quadrature methods for high-dimensional Gaussian integration

You may want to use a stochastic algorithm. Entry points to the literature (which is large) could be A stochastic algorithm for high-dimensional integrals over unbounded regions with Gaussian weight …
Carlo Beenakker's user avatar
1 vote
Accepted

Proving that $\lim_{j \to i} Z_{ij} = [\ln(\frac{\Delta s_i}{2})-1]\Delta s_i$

You want the relation between $\phi(x)$ evaluated at a point $x$ on the boundary and the derivative $\partial\phi/\partial n$ evaulated at the same point $x$, which is given by $$\phi(x)=\frac{\partia …
Carlo Beenakker's user avatar
2 votes
Accepted

Integrating a B-Spline basis function with respect to the standard normal PDF

Since a B-spline is a piecewise polynomial function, the question is whether there exists an exact equality formula for the integral $\int_{-a}^{b}u^pe^{-u^2/2}du$. This integral equals an elementary …
Carlo Beenakker's user avatar
0 votes
Accepted

Numerically bounding a Exponential-Trigonometric Integral

The limit is $$\lim_{n\rightarrow\infty} \int_0^{\pi/2} \frac{e^x}{\left(2x/\pi\right)^n + 1} \left| \sin(x) \sin(nx) \sin(2nx) \right| \, dx=\frac{2 \left(1+e^{\pi /2}\right)}{3 \pi }=1.23302\cdots.$ …
Carlo Beenakker's user avatar