Understanding Dirac notation - Product of ops. is product of matrices

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SUMMARY

The discussion focuses on the relationship between Dirac notation and matrix representation of operators, specifically in the context of quantum mechanics as presented by Shankar. It establishes that the product of two operators in Dirac notation corresponds directly to the multiplication of their respective matrices. The key equation discussed is (Ωλ)_{ij} = ∑(over k) = ∑(over k) Ω_{ik}λ_{kj}, which illustrates this concept. Participants seek clarification on the proof's details and formatting issues related to the notation.

PREREQUISITES
  • Understanding of Dirac notation in quantum mechanics
  • Familiarity with matrix multiplication
  • Basic knowledge of linear operators
  • Proficiency in quantum mechanics principles as outlined in Shankar's texts
NEXT STEPS
  • Study the derivation of operator products in Dirac notation
  • Explore matrix representations of quantum operators
  • Learn about the implications of linear operators in quantum mechanics
  • Review Shankar's "Principles of Quantum Mechanics" for detailed examples
USEFUL FOR

Students of quantum mechanics, physicists working with linear algebra in quantum systems, and anyone seeking to deepen their understanding of Dirac notation and operator theory.

ThereIam
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Homework Statement


This makes intuitive sense to me, but I am getting stuck when trying to read the Dirac notation proof.

Anyway, the author (Shankar) is just demonstrating that the product of two operators is equal to the product of the matrices representing the factors.

Homework Equations



(Ωλ)_{ij} = <i|Ωλ|j> = <i|ΩIλ|j> =

(and this is the part I don't understand)

\sum(over k) <i|Ω|k><k|λ|j> = \sum (over k) Ω_{ik}λ_{kj}

I apologize if the formatting didn't work. I'll try to fix it asap.

The Attempt at a Solution

 
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Could you be more precise as to what you don't understand?
 

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