How Does Cholesky Factorization Demonstrate Matrix Norm Inequalities?

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SUMMARY

The discussion focuses on demonstrating matrix norm inequalities using Cholesky factorization for a Hermitian positive-definite matrix A. The Cholesky factorizations are defined as A11 = L1L*1 and A22 = L2L*2, with the relationship A22 - A*12 A-111 A12 = L3L*3. The key conclusion is that the inequality ||A22 - A*12 A-111 A12||2 ≤ ||A||2 holds true by applying the submultiplicative and triangle inequalities.

PREREQUISITES
  • Understanding of Hermitian positive-definite matrices
  • Knowledge of Cholesky factorization
  • Familiarity with matrix norms, specifically ||.||2
  • Proficiency in applying submultiplicative and triangle inequalities
NEXT STEPS
  • Study the properties of Hermitian matrices and their implications
  • Learn more about Cholesky factorization techniques and applications
  • Research matrix norm inequalities and their proofs
  • Explore advanced topics in linear algebra, such as spectral theory
USEFUL FOR

Students and professionals in mathematics, particularly those studying linear algebra, matrix theory, and numerical methods. This discussion is beneficial for anyone looking to deepen their understanding of matrix inequalities and Cholesky factorization.

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Homework Statement


Let A =[A11 A12; A*12 A22] be Hermitian Positive-definite.
Use Cholesky factorizations
A11 = L1L*1
A22 = L2L*2
A22-A*12 A-111 A12 = L3L*3

to show the following:

||A22-A*12 A-111 A12||2≤||A||2

Homework Equations


The Attempt at a Solution



Using the submultiplicative and triangle inequalities:

||A22||2+||A*12||2 ||A-111||2||A12||2≤||A||2
 
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