# Jon

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bio website marcofrasca.wordpress.com location age member for 1 year, 5 months seen 1 hour ago profile views 674

I am a theoretical physicist working in the area of quantum field theory, mostly QCD and gauge theories. I am also interested in mathematical problems related to the solution of PDEs.

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 Aug3 answered Solution to a second order semilinear elliptic PDE Jul30 comment Solution to a second order semilinear elliptic PDEAre you sure about the last term in your equation? Shouldn't it be $u(u_r)^2$ rather than $u^2(u_r)$? Jul29 comment Laplace transform of a product of Modified Bessel Functions@J.M.: Thanks for your comment. I did it taking into account that I worked this out with Mathematica and held the further definition taken Wikipedia. Jul29 revised Laplace transform of a product of Modified Bessel FunctionsEdited the definition of the elliptic integral Jul28 comment Wiener process questionThis is not so. "cumsum" is always needed as you are describing a trajectory that, while has not derivative, is anyway continuous. The other way is just to write dW2(j)=dW2(j)+W2(j-1) and plotting dW2 but is not so efficient. You can find some code at marcofrasca.wordpress.com/2012/02/02/… and comments there. Jul28 comment Wiener process questionYou have to sum all the increments. This is the reason why the first code works ("cumsum") and the the second one does not. Jul27 comment Laplace transform of a product of Modified Bessel FunctionsI think Sasha's answer fits the bill. Jul27 answered Laplace transform of a product of Modified Bessel Functions Jul27 comment Show $1 + 2 \sum_{n=1}^N \cos n x = \frac{ \sin (N + 1/2) x }{\sin \frac{x}{2}}$ for $x \neq 0$This can be reduced to a geometric series just noting that $\cos nx =\frac{e^{inx}+e^{-inx}}{2}$. Jul27 revised Integral equation with a constraintMinor correction Jul26 revised Integral equation with a constraintAdded an existence condition Jul26 answered Integral equation with a constraint Jul25 comment Is there a known closed form number for $\prod\limits_{k=2}^{ \infty } \sqrt[k^2]{k}$Try using Euler-Maclaurin formula en.wikipedia.org/wiki/Euler%E2%80%93Maclaurin_formula. Jul23 accepted Moving to a conformal metric Jul22 comment Moving to a conformal metricYes, the content of this answer is not worth downvote being very near to my aims and of course, flagging it as spam is blatantly wrong. I understand that Chandra was a physicist and the cited book is about physics, but this guy should be treated somewhat better. Jul20 comment Moving to a conformal metricThanks Leonid. I will check the approach devised in Wikipedia. The reference you gave seems really interesting. Jul19 comment Moving to a conformal metric@WillieWong: My problem is that I have the metric given and I would like to turn it into a conformal shape in order to apply a theorem on Cramer-Rao optimal estimators. So, if I would have a quite general result, I should be able to accomplish the task. Jul19 comment Moving to a conformal metric@WillieWong: I am aware of this. But can they always be given explicitly in this case? Jul19 asked Moving to a conformal metric Jul11 revised The puzzling eigenvalues of a differential equation systemMinor correction