# All Questions

132,882 questions
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### Is Smoluchowski equation for aggregation conservative?

The Smoluchowski equation for the aggregation with no breakage can be written as $$\frac{dn_k}{dt}=\frac{1}{2}\Big(\sum_{i+j=k} n_i \beta_{ij}n_j\Big) - n_k \sum_{i=1}^N \beta_{ki} n_i$$ where $n_k$ ...
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### How large would the Moon have to be such that I could not see it in its entirety from earth?

The [^circumference of the] moon can be seen in its entirety from Earth [^during a full moon] taking up a very small portion of the visible sky. The Moon is ~1/4 the diameter of the Earth. If for the ...
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### Cutkosky's rule for vertex correction

I don't understand how to evaluate the diagram for electron-photon vertex with help of Cutosky's rule: According to the rule, one should cut diagram "in the middle". I denote final state as F and ...