Is (\alpha AB)^* Equal to \bar{\alpha }B^*A^* for All n × n Complex Matrices?

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Homework Help Overview

The discussion revolves around the equality of the adjoint of a product of matrices, specifically examining whether (\alpha AB)^* equals \bar{\alpha }B^*A^* for n × n complex matrices A and B.

Discussion Character

  • Exploratory, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the use of test matrices to understand the problem, with one participant questioning the validity of this approach for proving the statement for all n × n matrices. Another suggests starting with a simpler case involving a single matrix.

Discussion Status

The discussion is ongoing, with participants sharing initial thoughts and attempts at reasoning. Some guidance has been provided regarding breaking down the problem into simpler components, but no consensus or resolution has been reached.

Contextual Notes

Participants are considering the implications of proving the statement for arbitrary n × n matrices and the challenges associated with using specific examples.

DanielFaraday
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Homework Statement



Prove the following:

For every n × n complex matrices A and B, [tex](\alpha AB)^*=\bar{\alpha }B^*A^*[/tex].

Homework Equations



None

The Attempt at a Solution



Okay, I'm just getting started on this problem. All the ideas I have come up with so far involve using two "test" matrices. The problem with this is that it doesn't prove it for any n × n matrix. Does this matter?
 
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Ok, start small. Can you prove [tex] (\alpha A)^*=\bar{\alpha }A^*[/tex]

If you can, then you can just focus on proving that A and B swap like that
 
Hmm...

This feels like trying to prove 1+1=2. It just is! I'm still working on it...
 
Do you think this is a sufficient proof?

[tex] (\alpha AB)^*=\bar{\alpha }\overline{AB}=\bar{\alpha }\left(\bar{A}\right)\left(\bar{B}\right)=\bar{\alpha }\left(\left(\bar{A}\right)^T\right)^T\left(\left(\bar{B}\right)^T\right)^T=\bar{\alpha }\left(A^*\right)^T\left(B^*\right)^T=\bar{\alpha }\left(B^*A^*\right)^T[/tex]
 

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