Gram–Schmidt Process for Orthonormalizing Vectors in R^n

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Discussion Overview

The discussion centers on the applicability of the Gram–Schmidt process for orthonormalizing a finite set of linearly independent vectors in spaces defined by nondegenerate sesquilinear forms or symmetric bilinear forms that are not necessarily positive definite. The conversation explores whether the process can be generalized beyond the standard positive definite inner product.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the Gram–Schmidt process can be applied when the inner product is not positive definite, providing a specific example in R2.
  • Another participant asserts that the process works as long as there is a valid inner product.
  • A follow-up inquiry seeks clarification on the implications of dropping the positive definiteness assumption for the inner product.
  • Another participant notes that obtaining unit length vectors involves dividing by the length.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the Gram–Schmidt process without the positive definiteness condition, indicating that the discussion remains unresolved.

Contextual Notes

The discussion does not clarify the specific conditions under which the Gram–Schmidt process may or may not be valid outside of positive definiteness, leaving assumptions and definitions open to interpretation.

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http://en.wikipedia.org/wiki/Gram-Schmidt_process

Can Gram–Schmidt process be used to orthonormalize a finite set of linearly independent vectors in a space with any nondegenerate sesquilinear form / symmetric bilinear form not necessarily positive definite?

For example in R^2 define
[tex]\langle a, b\rangle = - a_1\times a_1 + a_2\times a_2[/tex]

From [tex]\{v_1, v_2\}[/tex] to [tex]\{e_1, e_2\}[/tex], assume v's are not null.
[tex]e_1 = \frac{v_1}{|v_1|}[/tex]
where [tex]|v_1| = \sqrt{|\langle v_1, v_1\rangle|}[/tex]
[tex]t_2 = v_2 - \frac{\langle v_1, v_2\rangle}{\langle v_1, v_1\rangle}v_1[/tex]
[tex]e_2 = \frac{t_2}{|t_2|}[/tex]

It looks like it can be generalized to R^n without any problem.
 
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In general, as long as you have a valid inner product, it works.
 
Yes, I'm asking if we drop the assumption of positive definiteness of inner product, will it work?
 
well to get unit length vectors you divide by the length.
 

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