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 Dec17 comment Definite integral over triple products of higher order Bessel functions. Thank you for your answer. May28 comment General expression for hypergeometric function ${}_1F{}_1(p, 1, x)$ when p is an integer it seems the answer is Sum[(-x)^k/k!/(k + 1) Binomial[p, k], {k, 0, p}]==Hypergeometric1F1[-p, 2, x] May27 comment General expression for hypergeometric function ${}_1F{}_1(p, 1, x)$ when p is an integer Ok never mind! What motivated the conjecture? May27 comment General expression for hypergeometric function ${}_1F{}_1(p, 1, x)$ when p is an integer Would you know what Hypergeometric1F1[p, 2, x] could be? Its the only other one I need :-) May27 comment General expression for hypergeometric function ${}_1F{}_1(p, 1, x)$ when p is an integer More generally its If[p > 0, Exp[x] LaguerreL[p - 1, -x], LaguerreL[-p, x]] for negative p to work as well. May27 comment General expression for hypergeometric function ${}_1F{}_1(p, 1, x)$ when p is an integer Thanks so much! Its related to the spin of galaxies in large scales structures as it happens May26 comment What is the generalization of Gauss's Theorem to a manifold? I friend of mine (whom I passed your question) tells me that the answer to your question is on p. 147 & 148 of “Geometrical methods of mathematical physics” by Bernard Schutz. Regards Apr6 comment Perturbation theory PDEs I would argue this was not your original post. Mar27 comment Perturbation theory PDEs If you apply the above procedure iteratively n times it will provide you with a solution up to order ϵ^n. What would be a converged solution in your view? Compared to a numerical solution? Mar27 comment Perturbation theory PDEs It obeys the original equation at order ϵ^2 so that is more or less the definition of a perturbative solution. Note that the method would also work for the full blown problem of Ψ(r,t,p) it would just be more messy. Mar26 comment Perturbation theory PDEs @Lipschitz could you please explain to me why my answer is not answering your question? Mar23 comment Perturbation theory PDEs @Lipschitz it is rigorous! At least for a physicist :-) Mar23 comment Perturbation theory PDEs But your question claims actual solution is known, so I it is fair to assume the square is known too? Mar23 comment Perturbation theory PDEs Naively (as a physicist), one would write $\Psi=\Psi_0+\epsilon \Psi_1$. Replace in original equation assuming $\Psi_0$ solves original equation. Get a new (linear) equation for $\Psi_1$ involving r.h.s. with (known) $\Psi_0^2$… iterate? Sep17 comment Evaluate $\int_1^\infty \cosh^{-1}(x) \ln(x^2-1) \exp \left(- \frac{x}{T} \right) dx$ Thanks! Very impressive! FYI this computation was needed for this paper fr.arxiv.org/pdf/1211.7352 for which we gave up presenting the corresponding anisotropic closed form. Dec15 comment Change of variables in Belousov-Zhabotinsky reaction Could you please change you title to something more specific? Thanks Nov27 comment Definite integral over triple products of higher order Bessel functions. @Phira thanks for the advice; it seems difficult to do in practice since 3 such functions are involved?? Nov27 comment Integral over triple product of spherical Bessel functions Thanks a lot! It always looks so simple in retrospect; I feel a bit embarrassed. Jun29 comment Evaluate $\int_1^\infty \cosh^{-1}(x) \ln(x^2-1) \exp \left(- \frac{x}{T} \right) dx$ It arises in the context of Faraday polarization transfer. Jun4 comment Does the integral of PDF of multi-normal distribution over quarter planes have a closed form? Nor does its cumulative distribution reduces to any analytic form?