Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2011

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Integral with singularities

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116695] Re: Integral with singularities
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Thu, 24 Feb 2011 06:22:41 -0500 (EST)

What are your values for a and b? Without those, we can't duplicate your  
situation.

Bobby

On Wed, 23 Feb 2011 04:24:46 -0600, gmarkowsky at gmail.com  
<gmarkowsky at gmail.com> wrote:

> Hello all,
>
> I am doing
>
> NIntegrate[
>  1/Sqrt[(x^2 + y^2) ((x - 1)^2 +
>       y^2) ((x - a)^2 + (y - b)^2)], {x, -3, 3}, {y, -3, 3}]
>
> Somehow it is not working very well. This doesn't seem to be a  
> particularly difficult request but Mathematica is having trouble. It  
> keeps saying stuff like
>
> NIntegrate::slwcon: Numerical integration converging too slowly; suspect  
> one of the following: singularity, value of the integration is 0, highly  
> oscillatory integrand, or WorkingPrecision too small. >>
>
> NIntegrate::ncvb: NIntegrate failed to converge to prescribed accuracy  
> after 18 recursive bisections in x near {x,y} = {1.,2.06474}. NIntegrate  
> obtained 76.80413981137505` and 101.86483781265876` for the integral and  
> error estimates. >>
>
> I guess that near 0, 1, and a+bi the integrand blows up. I have tried to  
> exclude small areas around those points, but I don't seem to be doing it  
> right. Can anyone help?
>
> Greg
>


-- 
DrMajorBob at yahoo.com


  • Prev by Date: Re: Mathematica Weirdness
  • Next by Date: Re: weibull plot on weibull scaled paper
  • Previous by thread: Re: Integral with singularities
  • Next by thread: How to local files on ParallelKernels