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   Re: eigenvalues property ?
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   Author  Topic: Re: eigenvalues property ?  (Read 2214 times)
MonicaMath
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Re: eigenvalues property ?  
« on: Mar 28th, 2009, 8:29pm »
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maybe you can start with:
 
since r is not an eigenvalue for A then det(r*I - A) not zero, so (A-r*I) is nonsingular, and use the fact that Bx=r*x, then show that  
|| inv(r*I - A) (B-A) ||<1  to obtain a contradiction.
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trusure
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Re: eigenvalues property ?  
« Reply #1 on: Mar 28th, 2009, 9:33pm »
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I tried your method but there is no result ?!
 
can anyone give me a hint ! Roll Eyes
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Eigenray
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Re: eigenvalues property ?  
« Reply #2 on: Mar 29th, 2009, 5:31pm »
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Well that's a funny problem.  Note that  
 
(r I - A)-1(B-A)
 = (r I - A)-1( (r I - A) + (B - r I) )
 = I + C,
where C = (r I - A)-1(B - r I) is a singular matrix.  Do you know the following result: if || I + C || < 1, then C is non-singular?
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