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I'm trying to do the following integral, but Mathematica won't evaluate it - it just spits out the actual symbolic integral.

$$\frac{e^{-\frac{(k-d)^2}{2 a^2}} \left | \frac{-d+\frac{c i}{2}+k-\frac{i b}{2}}{-d+\frac{b i}{2}+\frac{c i}{2}+k}+1 \right | ^2}{4 \sqrt{2 \pi } \sqrt{a^2}}, a = 1, b = 1, c = 0, d = 0.0001$$

a = 1;
b = 1;
c = 0;
d = 0.0001;

Integrate[((2*Pi*a^2)^(-1/4)*
     Exp[-(k - d)^2/(4*a^2)])^2 * (Abs[
      1 + ((k - d + (I*c/2) - (I*b/2))/ (k - d + (I*c/2) + (I*b/2)))]/
     2)^2, {k, 0, Infinity} ]

$$\int_0^{\infty } \frac{e^{-\frac{1}{2} (k-0.0001)^2} \left | \frac{(-0.0001-0.5 i)+k}{(-0.0001+0.5 i)+k}+1\right | ^2}{4 \sqrt{2 \pi }} \, dk$$

Can anyone tell me what I'm doing wrong?

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  • $\begingroup$ First,use NIntegrate.second,it is bad idea that put Abs in Integrate. $\endgroup$
    – Apple
    Commented Mar 14, 2014 at 4:17
  • $\begingroup$ Thanks. What's the problem with Abs and Integrate? $\endgroup$
    – JuanMunoz
    Commented Mar 14, 2014 at 4:27

1 Answer 1

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Use NIntegrate, it can do it

a = 1;
b = 1;
c = 0;
d = 1/10000;

int = ((2*Pi*a^2)^(-1/4)*Exp[-(k - d)^2/(4*a^2)])^2*
  (Abs[1 + ((k - d + (I*c/2) - (I*b/2))/(k - d + (I*c/2) + (I*b/2)))]/2)^2;
NIntegrate[int, {k, 0, Infinity}]
(* 0.280909 + 0. I *)

Integrate could not find closed form solution

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  • $\begingroup$ OK, thanks, it works now :) $\endgroup$
    – JuanMunoz
    Commented Mar 14, 2014 at 4:27

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