Curl of the transpose of a gradient of a vector: demonstration of an identity

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Discussion Overview

The discussion revolves around the demonstration of an identity related to the curl of the transpose of a gradient of a vector, specifically using indicial notation. Participants are exploring concepts in tensor analysis as they relate to continuum mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks feedback on their attempt to demonstrate an identity using indicial notation and expresses a desire to understand tensors better.
  • Another participant questions the type of vector product being used, specifically referring to the notation \hat{e}_i \hat{e}_j.
  • A participant mentions using the tensor product in their approach.
  • Several participants express frustration over the perceived difficulty of the question and request assistance.
  • One participant provides a link to an external resource that may clarify the topic for another participant.
  • There is confusion regarding the definitions of \nabla(\nabla\times\mathbf{u}) and \nabla \mathbf{u}, with a participant attempting to clarify their understanding of these terms.
  • Another participant notes conflicting definitions of the curl of a tensor and expresses intent to contact the authors of these definitions for clarification.
  • A later reply indicates that the question is not trivial and acknowledges the existence of different definitions of the curl of a tensor.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the definitions and concepts involved, indicating that multiple competing views remain without a clear consensus on the definitions of the curl of a tensor.

Contextual Notes

Participants highlight limitations in their understanding, particularly regarding the definitions of vector products and the curl of tensors, which may depend on specific contexts or sources.

traianus
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I would like to demonstrate an identity with the INDICIAL NOTATION. I have attached my attempt. Please let me know where I made mistakes. Any suggestion? I am trying to understand tensors all by myself because they are the keys in continuum mechanics
Thanks
 

Attachments

Last edited:
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What sort of vector product are you using here [itex]\hat{e}_i \hat{e}_j[/itex]?
 
tensor product
 
Is this question so difficult? Please help me: I am trying to learn tensors and I would like to know what my mistake is. Thanks!
 
Any suggestion?
 
Can anyone suggest a forum to post my question? Thanks
 
anything? please help!
 
?
 
Is my question too difficult? Please advise.
 
  • #10
I don't really understand what is meant by
[tex]\nabla(\nabla\times\mathbf{u})[/tex]
and
[tex]\nabla \mathbf{u}[/tex].

For example, if [tex]\mathbf{u}=u_j\hat{e}_j[/tex], then [tex]\nabla \mathbf{u}=(\partial_i\hat{e}_i)(u_j\hat{e}_j)=\partial_iu_j\hat{e}_i\hat{e}_j[/tex].

But what is [tex]\hat{e}_i\hat{e}_j[/tex]; the inner product between the unit basis vectors? Then the result would be a scalar instead of a vector.
 
Last edited:
  • #12
Any other input?
 
  • #13
?
 
  • #14
You should at least explain how you define [itex]\nabla u[/itex] when u is a vector.
 
  • #15
The problem is at the very bottom line in the definition of a curl of a tensor. I found 2 definitions which contradict to each other. Mine is one of them. I will email the authors.
 
  • #16
I asked an expert. The question was not trivial. After a while I found out that there are different definitions of curl of a tensor.
 

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