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Coefficients of determinant polynomial are zero for higher order matrix?

Posted 9 years ago

I am solving a homogeneous system of linear equations of order 14n x 14n. I need to find out the values of one parameter for which determinant is zero. But after n=2, all the coefficient of the characteristic polynomial are becoming zero, which is unexpected. Elements of the matrix are integrals involving Bessel's and modified Bessel's function. Is there a way to resolve it?

POSTED BY: neelam choudhary
5 Replies

Maybe.

That's about the best one can say absent serious detail, preferably in the form of Mathematica code. Note that such can be attached as a Mathematica notebook if too large for the post itself.

POSTED BY: Daniel Lichtblau

Code is large, I cant post here. But it works well for n=1,2 and gives good results.

POSTED BY: neelam choudhary

Dear Daniel, Code is attached herewith. I want to increase 'n' to find 'w' which is required. I kindly request you to please let me know the issue of code.

Attachments:
POSTED BY: neelam choudhary

The issue is obvious if you scan over the code. Pay careful attention to red coloring. It shows up in every use of the function Abs, wherein brackets are not used to enclose the arguments.

There are probably numeric problems as well, since there appears to be a mix of exact and approximate methods. Might try wirking with NIntegrate[...] rather than N[Integrate[...]] for example. Or give exact input and use Integrate[...], and don't numericize until necessary. But this might be too slow.

The code as written is quite overly complicated, so it's really hard to say what else might be going on. First thing would be to make appropriate use of Table and get rid of all the For loops.

POSTED BY: Daniel Lichtblau

I will work on your suggestions. Thanks a lot.

POSTED BY: neelam choudhary
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