How does this change of coordinates work?

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I have the following integral:

$$\displaystyle \int_{\mathbb{R}^2} \left( \int_{\mathbb{R}^2} \frac{J_{1}(\rho |\alpha|)J_{1}(\rho|k- \alpha|)}{|\alpha||k-\alpha|} \ \mathrm{d}\alpha \right)^2 \ \mathrm{d}k,$$

with $\alpha, k \in \mathbb{R}^2$, $\rho$ constant, $J_{\nu}$ the Bessel function of the first kind, $|\cdot|$ the Euclidean norm on $\mathbb{R}^2$.

I want to make the substitution $\alpha = s$, $k = s + t$. If the square wasn't there, this would be easy, and we'd just end up with

$$\displaystyle \int_{\mathbb{R}^2} \int_{\mathbb{R}^2} \frac{J_{1}(\rho |s|)J_{1}(\rho|t|)}{|s||t|} \ \mathrm{d}s \ \mathrm{d}t,$$

since the determinant of the Jacobian corresponding to this change of coordinates is $1$. But the square makes things difficult. What does the integral at the top look like after making that change of coordinates?

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IMHO, you should consider apart the transformation of the inside integral.

What follows is a hint, far from a full answer.

2 remarks:

1) $f(\omega)=\pi\dfrac{\sqrt{3}}{2}r^{3/2}\dfrac{J_1(2 \pi \omega r)}{2 \pi \omega r}$ is the Fourier transform of a unit disk with radius $r$.

(http://isi.ssl.berkeley.edu/~tatebe/whitepapers/FT%20of%20Uniform%20Disk.pdf).

2) The inside integral is, up to a multiplicative constant, the convolution of two such transforms, otherwise said, it is a square of convolution.

Thus, the integral can be written, up to a multiplicative constant, as the integral of the Fourier transform of a the area common to two disks with radius $r$, this function being explicitly computable.