(adsbygoogle = window.adsbygoogle || []).push({}); why no change of variable to polar coordinates inside multi-loop integral ??

given a mul,ti-loop integral

[tex] \int d^{4}k_{1} \int d^{4}k_{2}.................\int d^{4}k_{n}f(k_{1} , k_{2},.....,k_{n}) [/tex]

which can be considered a 4n integral for integer n , my question is why can just this be evaluated by using a change of variable to 4n- polar coordinates ?

one we have made a change of variable and calculated the Jacobian, and integrated over ALL the angular variables we just have to make an integral

[tex] \int_{0}^{\infty}drg(r)r^{4n-1} [/tex] which is just easier to handle

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# Why no change of variable to polar coordinates inside multi-loop integral ?

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