Are These Sets of Matrices Closed Under Multiplication?

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SUMMARY

The discussion focuses on the closure properties of specific sets of matrices under multiplication, specifically circulant matrices, upper triangular matrices, and Hessenberg matrices. It is established that upper triangular matrices are closed under multiplication, as the product of two upper triangular matrices is also upper triangular. The closure properties of circulant and Hessenberg matrices are questioned, with a need for further exploration into whether their products yield matrices of the same type.

PREREQUISITES
  • Understanding of matrix multiplication
  • Familiarity with types of matrices, specifically circulant, upper triangular, and Hessenberg matrices
  • Knowledge of linear algebra concepts
  • Ability to apply definitions of matrix types in proofs
NEXT STEPS
  • Research the properties of circulant matrices and their closure under multiplication
  • Explore the characteristics of Hessenberg matrices and their behavior under multiplication
  • Study proofs related to the closure of upper triangular matrices under multiplication
  • Investigate general closure properties of matrix sets in linear algebra
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Students and professionals in mathematics, particularly those studying linear algebra, matrix theory, and anyone interested in the properties of matrix operations.

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A set S of (necessarily square) matrices is said to be closed under multiplication if AB∈ S whenever A, B ∈ S.

Which of these matrices are closed under multiplication?

Circulant matrices
Upper triangular matrices
Hessenberg matrices

My trouble: How do I go about figuring this one out?
 
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"A set S of (necessarily square) matrices is said to be closed under multiplication if AB∈ S whenever A, B ∈ S."

Perhaps you mean that the multiplication of 2 matrices of the same type will give as result a matrix of the same type.If that's so, then all triangular matrices are closed under multiplication (it can be proved, just have to use the definitions of triangular matrices and matrix pultiplication).
I'm not familiar with the other types os matrices.

Best regards
 
you mean "which of these sets of matrices is closed under multiplication".

If you multiply two circulant matrices is the result always a circulant matrix?

If you multiply two Hessenberg matrices is the result always a Hessenberg matrix?
 

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