What symbol is used for linear operator actions?

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Discussion Overview

The discussion revolves around the notation used for linear operator actions, specifically in the context of a vector function and its mapping by an operator. Participants explore the appropriate symbols for expressing these operations, including the tensor product and matrix-vector multiplication.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant introduces a vector function v and an operator G, asking about the commonly used symbol for the mapping G(v).
  • Another participant suggests that using G(v) is acceptable.
  • A participant clarifies that G is a 3x3 matrix-valued operator and questions the appropriateness of the tensor product \otimes for expressing the operation.
  • Some participants argue that neither the tensor product nor the dot product is suitable, advocating for the use of G(v) instead.
  • A participant expresses a desire to emphasize matrix-vector multiplication but agrees to use G(v) to avoid ambiguity.
  • A later reply confirms that the notation G^n(v) is found in a textbook, indicating a common understanding of applying the operator multiple times.

Areas of Agreement / Disagreement

Participants generally agree that G(v) is the most appropriate notation, while there is contention regarding the use of the tensor product and dot product. The discussion remains unresolved on the necessity of emphasizing the matrix-vector multiplication aspect.

Contextual Notes

There are limitations regarding the definitions of the symbols discussed and the context in which they are applied, particularly concerning the operator's matrix representation and the implications of using different notations.

sunjin09
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Given a vector v[itex]\in H[/itex]: R2->R3 which is a function from R2 to R3, and an operator G: H->H on the space H in which v lives, what is the most commonly used symbol to refer to this mapping, i.e., G(v)=G[itex]\otimes v[/itex] or something else?
 
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G(v) is fine.
 
Thank you for replying, but I want to emphasize that G is a 3x3 matrix valued operator that multiplies the 3x1 vector valued function v then integrated over the entire domain, is the tensor product [itex]\otimes[/itex] appropriate? I used a dot but was complained about by the reviewer.
 
The tensor product is not appropriate, neither is the dot. Using G(v) makes most sense. Is there a reason why you don't want to use G(v)?
 
Thanks again for clarifying, I guess I just wanted to emphasize the matrix vector multiplication part, I'll use G(v) so that there's no ambiguity. One more question though, if I apply G n times to v, n>=0, is [itex]G^n(v)[/itex] appropriate?
 
I found the notation G^n(v)=G(G(G...G(v)...)) in a textbook. Thank you both!
 

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