Proving an Identity Involving Matrices and Inner Products

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SUMMARY

The discussion centers on proving the identity \(\langle Ax,y \rangle = \langle x,A^*y \rangle\), where \(A\) is an \(n \times n\) matrix over \(\mathbb{C}\), and \(A^*\) is its conjugate transpose. Participants clarify that the standard inner product on \(\mathbb{C}^n\) can be expressed as \(\langle a, b \rangle = a^\dagger b\) or \(\langle a, b \rangle = a^t \bar{y}\). The proof is confirmed to be valid using these definitions, demonstrating the equivalence of the two expressions.

PREREQUISITES
  • Understanding of linear algebra concepts, specifically matrix operations.
  • Familiarity with inner product spaces, particularly in \(\mathbb{C}^n\).
  • Knowledge of conjugate transposes of matrices.
  • Proficiency in complex number arithmetic.
NEXT STEPS
  • Study the properties of inner products in complex vector spaces.
  • Learn about the implications of the conjugate transpose in matrix theory.
  • Explore proofs of other identities involving matrices and inner products.
  • Investigate applications of inner product spaces in quantum mechanics.
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Mathematicians, physics students, and anyone involved in linear algebra or quantum mechanics who seeks to deepen their understanding of matrix identities and inner product spaces.

devious_
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Is there a non-ugly proof of the following identity:
\langle Ax,y \rangle = \langle x,A^*y \rangle
where A is an nxn matrix over, say, \mathbb{C}, A* is its conjugate transpose, and \langle \cdot , \cdot \rangle is the standard inner product on \mathbb{C} ^n.
 
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Just start writing out the left side using <a,b>=a^\dagger b.
 
Thanks.

Although using my definition for the standard inner product I had to use \langle a , b \rangle = a^t \bar{y}, but it all worked out in the end.
 

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