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For questions about problems related to physics that involve evaluating integrals. Purely mathematical questions should be asked at math.SE.

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How to compute this form factor?

You can use the fact $$ \int e^{-iqr \cos\theta} \sin \theta d\theta = -\int e^{-iqr c} dc $$ where $c$ is the integration variable that replaced $\cos\theta$. The integral is now elementary. …
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2 votes
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Probability density function (pdf) of a Wiener process

Given the normally distributed random variable $Z\sim {N}(\mu,\sigma^2)$, it is possible to show that its moment-generating function is $$\langle \exp({tZ})\rangle=\exp({\mu t + \sigma^2 t^2/2})=\exp …
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14 votes

Why aren't Runge-Kutta methods used for molecular dynamics simulations?

In molecular dynamics you have to evolve a large number of particles, so efficiency is important. The Verlet algorithm provides numerical stability, as well as other properties that are important in …
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23 votes
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If charges is quantised, how can we use integrals in electrostatics?

You may also wonder why we use the concept of density of a material despite that material is made of molecules, or atoms, or in general quantized entities. This is the basis of hydrodynamics and solid …
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2 votes

Complex coordinates $ds^2 = dzdz̄$ in 2d

Consider $z=x+i y$ and $\bar z=x-iy$ ($x$ and $y$ are real). It is easy to show that: $$ dz\land d\bar z=(dx+i\,dy)\land(dx-i\,dy) =dx\land dx+i \, dy\land dx -i \, dx\land dy-dy\land dy. $$ However, …
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