Showing Levi-Civita properties in 4 dimensions

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Homework Help Overview

The discussion revolves around properties of the Levi-Civita symbol in four dimensions, specifically focusing on verifying certain identities involving the symbol and Kronecker deltas. The original poster is attempting to show relationships between the Levi-Civita symbols and the Kronecker delta, questioning the correctness of their findings.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to prove identities involving the Levi-Civita symbol, expressing confusion over discrepancies between their results and expected outcomes. They question whether their statements might be incorrect.
  • Some participants suggest using matrix representations and simplifying, while others note the importance of considering the number of terms in anti-symmetrization.

Discussion Status

Participants are actively engaging with the original poster's reasoning, providing insights and suggestions for alternative approaches. There is acknowledgment of potential errors in the original poster's calculations, and some guidance has been offered regarding the structure of the proofs.

Contextual Notes

There is a focus on the implications of the dimension of the space (four dimensions) and how it affects the calculations involving the Kronecker delta. The original poster expresses uncertainty about the correctness of their results based on the properties of the Levi-Civita symbol.

Phys pilot
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first of all english is not my mother tongue sorry. I want to ask if you can help me with some of the properties of the levi-civita symbol.

I am showing that

$$\epsilon_{ijkl}\epsilon_{ijmn}=2!(\delta_{km}\delta_{ln}-\delta_{kn}\delta_{lm})$$

so i have this...

$$\epsilon_{ijkl}\epsilon_{ijmn}=\delta_{ii}\delta_{jj}\delta_{km}\delta_{ln}+\delta_{ij}\delta_{jm}\delta_{kn}\delta_{li}+\delta_{im}\delta_{jn}\delta_{ki}\delta_{lj}+\delta_{in}\delta_{ji}\delta_{kj}\delta_{lm}-\delta_{ii}\delta_{jn}\delta_{km}\delta_{lj}-\delta_{in}\delta_{jm}\delta_{kj}\delta_{li}-\delta_{im}\delta_{jj}\delta_{ki}\delta_{ln}-\delta_{ij}\delta_{ji}\delta_{kn}\delta_{lm}=3^2\delta_{km}\delta_{ln}+\delta_{kn}\delta_{lm}+\delta_{km}\delta_{ln}+\delta_{kn}\delta_{lm}-3\delta_{km}\delta_{ln}-\delta_{km}\delta_{ln}-3\delta_{km}\delta_{ln}-3\delta_{kn}\delta_{lm}=3\delta_{km}\delta_{ln}-3\delta_{kn}\delta_{lm}=3(\delta_{km}\delta_{ln}-\delta_{kn}\delta_{lm})$$

which is not equal to the supposedly correct answer. can the statement be wrong?
if not i can't see my error.

Also i need to prove that:

$$\epsilon_{ijkl}\epsilon_{ijkm}=3!\delta_{lm}$$
i know and i proved that
$$\epsilon_{ijkl}\epsilon_{ijkl}=24=4!$$
so if $l=m$ i have this
$$\epsilon_{ijkl}\epsilon_{ijkl}=3!\delta_{ll}=3!\cdot 3=18$$
which is not equal to 4!=24 so its the statement wrong again? it must be
$$\epsilon_{ijkl}\epsilon_{ijkm}=8\delta_{lm} $$
Actually i proved that:
$$\epsilon_{ijkl}\epsilon_{ijkm}=\delta_{ii}\delta_{jj}\delta_{kk}\delta_{lm}+\delta_{ij}\delta_{jk}\delta_{km}\delta_{li}+\delta_{ik}\delta_{jm}\delta_{ki}\delta_{lj}+\delta_{im}\delta_{ji}\delta_{kj}\delta_{lk}-\delta_{ii}\delta_{jm}\delta_{kk}\delta_{lj}-\delta_{im}\delta_{jk}\delta_{kj}\delta_{li}-\delta_{ik}\delta_{jj}\delta_{ki}\delta_{lm}-\delta_{ij}\delta_{ji}\delta_{km}\delta_{lk}=3^3\delta_{lm}+\delta_{ik}\delta_{km}\delta_{li}+\delta_{ii}\delta_{lj}\delta_{jm}+\delta_{jm}\delta_{kj}\delta_{lk}-3^2\delta_{lm}-\delta_{jj}\delta_{li}\delta_{im}-3\delta_{ii}\delta_{lm}-\delta_{ii}\delta_{lm}=3^3\delta_{lm}+\delta_{lk}\delta_{km}+\delta_{ii}\delta_{lm}+\delta_{lj}\delta_{jm}-3^2\delta_{lm}-3\delta_{lm}-3^2\delta_{lm}-3\delta_{lm}=3^3\delta_{lm}+\delta_{lm}+3\delta_{lm}+\delta_{lm}-3^2\delta_{lm}-3\delta_{lm}-3^2\delta_{lm}-3\delta_{lm}=8\delta_{lm} $$
Even more if i use my solution:

$$\epsilon_{ijkl}\epsilon_{ijmn}=3(\delta_{km}\delta_{ln}-\delta_{kn}\delta_{lm})$$
to prove
$$\epsilon_{ijkl}\epsilon_{ijkm}=3!\delta_{lm}$$
using $m=k$ and $n=m$ i have this
$$3(\delta_{km}\delta_{ln}-\delta_{kn}\delta_{lm})$$
$$3(\delta_{kk}\delta_{lm}-\delta_{km}\delta_{lk})$$
$$3(3\delta_{lm}-\delta_{lm})$$
$$3(2\delta_{lm})$$
$$6(\delta_{lm})=3!(\delta_{lm})$$
 
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Dr Transport said:
Start with the matrix representation using Kronecker deltas then simplify.

https://en.wikipedia.org/wiki/Levi-Civita_symbol#Four_dimensions
That's what i did but when i simplify i get the error and i don't know where i think that the statement is false because i repeat the product too many times and i always get the same
 
In 4 dimensions ##\delta_{ii} = 4##.
 
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Orodruin said:
In 4 dimensions ##\delta_{ii} = 4##.
that makes sense but if $\delta_{ii}=4$
$$\epsilon_{ijkl}\epsilon_{ijkl}=\delta_{ii}\delta_{jj}\delta_{kk}\delta_{ll}+\delta_{ij}\delta_{jk}\delta_{kl}\delta_{li}+\delta_{ik}\delta_{jl}\delta_{ki}\delta_{lj}+\delta_{il}\delta_{ji}\delta_{kj}\delta_{lk}-\delta_{ii}\delta_{jl}\delta_{kk}\delta_{lj}-\delta_{il}\delta_{jk}\delta_{kj}\delta_{li}-\delta_{ik}\delta_{jj}\delta_{ki}\delta_{ll}-\delta_{ij}\delta_{ji}\delta_{kl}\delta_{lk}=4^4+\delta_{lj}\delta_{jl}+\delta_{ii}\delta_{jj}+\delta_{jl}\delta_{lj}-\delta_{ii}\delta_{jj}\delta_{kk}-\delta_{ii}\delta_{jj}-\delta_{ii}\delta_{jj}\delta_{ll}-\delta_{ii}\delta_{kk}=4^4+\delta_{ll}+4^2+\delta_{jj}-4^3-4^2-4^3-4^2=4^4+4+4^2+4-4^3-4^2-4^3-4^2=120=5!$$

And it should be 4!=24, actually if $\delta_{ii}=3$ it works
$$\epsilon_{ijkl}\epsilon_{ijkl}=\delta_{ii}\delta_{jj}\delta_{kk}\delta_{ll}+\delta_{ij}\delta_{jk}\delta_{kl}\delta_{li}+\delta_{ik}\delta_{jl}\delta_{ki}\delta_{lj}+\delta_{il}\delta_{ji}\delta_{kj}\delta_{lk}-\delta_{ii}\delta_{jl}\delta_{kk}\delta_{lj}-\delta_{il}\delta_{jk}\delta_{kj}\delta_{li}-\delta_{ik}\delta_{jj}\delta_{ki}\delta_{ll}-\delta_{ij}\delta_{ji}\delta_{kl}\delta_{lk}=3^4+\delta_{lj}\delta_{jl}+\delta_{ii}\delta_{jj}+\delta_{jl}\delta_{lj}-\delta_{ii}\delta_{jj}\delta_{kk}-\delta_{ii}\delta_{jj}-\delta_{ii}\delta_{jj}\delta_{ll}-\delta_{ii}\delta_{kk}=3^4+\delta_{ll}+3^2+\delta_{jj}-3^3-3^2-3^3-3^2=3^4+3+3^2+3-3^3-3^2-3^3-3^2=24=4!$$
 
You are missing terms. The anti-symmetrisation over the 4 indices should have 4! = 24 terms, not 8.
 
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Orodruin said:
You are missing terms. The anti-symmetrisation over the 4 indices should have 4! = 24 terms, not 8.
Yeah, its true, i am sorry.

i am going to do the determinant 4x4
gif&s=2&w=82.&h=76..gif
gif&s=2&w=446.&h=57..gif

and then simplify.
Thanks!
 

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