Show that this field is orthogonal to each vector field.

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Homework Help Overview

The problem involves demonstrating that a specific field, represented by the expression ε_{ijkl}a^{i}b^{k}c^{l}, is orthogonal to three vector fields a, b, and c within the context of a locally Minkowskain 4-manifold.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to show that the expression equals zero when multiplied by each vector field but expresses uncertainty about the method to achieve this.
  • Some participants discuss the properties of the antisymmetric tensor ε_{ijkl} and its implications for the expression involving the vector fields.
  • Questions arise regarding the manipulation of indices and the implications of antisymmetry in the context of the problem.

Discussion Status

The discussion is ongoing, with participants exploring the properties of the tensor and its relationship to the vector fields. Some guidance has been offered regarding the manipulation of indices, but no consensus or resolution has been reached yet.

Contextual Notes

Participants are considering the implications of the antisymmetry of the tensor ε_{ijkl} and how it affects the expression involving the vector fields. There is an emphasis on ensuring the correct handling of indices in the calculations.

gotmilk04
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Homework Statement


If a, b, and c are any three vector fields in locally Minkowskain 4-manifold, show that the field ε_{ijkl}a^{i}b^{k}c^{l} is orthogonal to \vec{a}, \vec{b}, and \vec{c}.


Homework Equations





The Attempt at a Solution


I know I have to show that multiplying the field by each individual vector field equals 0, but I don't know how to go about doing this.
 
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The tensor \epsilon_{ijkl} is totally antisymmetric. In particular, \epsilon_{ijkl}=-\epsilon_{jikl}. What does that imply about \epsilon_{ijkl}a^i a^j?
 
So then ε_{ijkl}a^{i}a^{j}= -ε_{jikl}a^{i}a^{j}?
 
gotmilk04 said:
So then ε_{ijkl}a^{i}a^{j}= -ε_{jikl}a^{i}a^{j}?

Yes, but also note that we can swap the indices that we're summing over:

\epsilon_{jikl} a^i a^j = \epsilon_{ijkl} a^j a^i .

You might want to do this in steps if it's not completely obvious (first change i to m, j to n, then n to i, m to j).

After you figure it out, put it all back together in the expression that you started with.
 

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