# Nuclear Transport

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1. Feb 6, 2015

### bamaguy

Show by direct calculation that Eqs. (4-134) and (4-137) in the textbook by Duderstadt and Hamilton hold, i.e.:

(a) ∫ dΩΩiΩj= 4π/3 δij; i,j = x,y,z;

(b) ∫ dΩΩxΩyΩz = 0, if l, m, or n is odd.

The integrals are over 4π.

This is part of the derivation of the diffusion equation from the neutron transport equation. Part (b) from D&H Next note that the integral of the product of any odd number of components of OMEGA vanishes by symmetry.

(a) I think that 4π/3 comes from the volume of the sphere and δij is the kronecker delta. I don't know how to show this mathematically.
(b)
I think that this has to do with the sin or cos function.

2. Feb 6, 2015

### DEvens

Not volume. Omega is solid angle.

http://en.wikipedia.org/wiki/Solid_angle

I don't have the textbook you cite. So it's a little difficult to follow the question. You should read back in the text to see if they don't do something on solid angle and how to manipulate it.

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