Double Integral: solution with hypergeometric function?

Dirickby
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Homework Statement


Hello, I've recently encountered this double integral
$$\int_0^1 dv \int_0^1 dw \frac{(vw)^n(1-v)^m}{(1-vw)^\alpha} $$

with ## \Re(n),\Re(m) \geq 0## and ##\alpha = 1,2,3##.

Homework Equations



I use Table of Integrals, Series and Products by Gradshteyn & Ryzhik as a reference. There I found that
$$\int_0^1 dv \frac{(v)^n(1-v)^m}{(1-vw)^\alpha} = \beta(n+1, m+1)
_2F_1(\alpha ,n+1; n+m+2; w) \qquad\text{(3.197.3)} $$
with the ##\beta##-function and ##_2F_1## the ordinary hypergeometric function. But this equation is only valid for ##w<1## (and ## \Re(n+1),\Re(m+1) > 0##, which is the case here).

The Attempt at a Solution


If I could use the formula above, I could easily integrate over ##v## and then over ##w##, but I suppose it would be wrong as ##w=1## at the upper integration limit. Can I somehow bypass this?
Additionnally if we were to only consider ##w=1##, the integral would diverge at least in some cases (e.g. ##m=0##). Could my whole integral diverge because of this?
 
Physics news on Phys.org
At w=1, the integral from Gradstein diverges logarithmically. But the integral over a logarithmic singularity is finite, so the integral over w should exist.
 
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There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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