Splitting sigmas

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In summary, the statement to be proven is that Tr(AB) = Tr(BA) for nxn matrices A and B. To prove this, the double sigma notation is used to manipulate the equations and it is possible to change the dummy indices to any other letter without altering the formula for Tr. This provides a helpful approach to proving the statement.
  • #1
Bipolarity
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Homework Statement

Prove the following statement, where A and B are nxn matrices.

[tex] Tr(AB) = Tr(BA) [/tex]

Homework Equations


The Attempt at a Solution


Using some manipulations, I arrived at
[tex] \sum^{n}_{p=1}\sum^{n}_{k=1}A_{pk}B_{kp} = \sum^{n}_{p=1}\sum^{n}_{k=1}B_{pk}A_{kp} [/tex]

If I can prove the above, I am done, but I have never worked with double sigma notations before, so any advice folks?

BiP
 
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  • #2
Bipolarity said:

Homework Statement

Prove the following statement, where A and B are nxn matrices.

[tex] Tr(AB) = Tr(BA) [/tex]



Homework Equations





The Attempt at a Solution


Using some manipulations, I arrived at
[tex] \sum^{n}_{p=1}\sum^{n}_{k=1}A_{pk}B_{kp} = \sum^{n}_{p=1}\sum^{n}_{k=1}B_{pk}A_{kp} [/tex]

If I can prove the above, I am done, but I have never worked with double sigma notations before, so any advice folks?

BiP

k and p are what are called 'dummy indices'. You can change k to any other letter, like q and you still have a good formula for Tr. Just interchange k and p.
 
  • #3
Dick said:
k and p are what are called 'dummy indices'. You can change k to any other letter, like q and you still have a good formula for Tr. Just interchange k and p.

Ah, ingenious! Thanks!

BiP
 

1. What is "Splitting sigmas"?

"Splitting sigmas" refers to a phenomenon observed in certain scientific experiments or simulations where the results show a split in the standard deviation (sigma) of a data set. This can occur due to a variety of factors, such as outliers, underlying subgroups, or measurement errors.

2. How is "Splitting sigmas" different from normal data distribution?

In a normal data distribution, the standard deviation (sigma) remains relatively consistent across the entire data set. In "Splitting sigmas", the standard deviation may vary significantly between different subsets of the data, resulting in a split or separation between the two or more sigmas.

3. Can "Splitting sigmas" affect the accuracy of scientific results?

Yes, "Splitting sigmas" can potentially affect the accuracy of scientific results by introducing bias or inconsistency in the data. It is important for scientists to identify and address any instances of "Splitting sigmas" to ensure the validity of their findings.

4. What are some potential causes of "Splitting sigmas"?

There are several potential causes of "Splitting sigmas", including the presence of outliers, differences in subgroups within the data, and measurement errors. It can also occur due to complex interactions between multiple variables in a system.

5. How can scientists address "Splitting sigmas" in their research?

Scientists can address "Splitting sigmas" by carefully examining their data for any potential sources of bias, outliers, or subgroups. They can also utilize statistical methods to identify and account for any significant variations in the standard deviation of their data. Additionally, replicating experiments and conducting sensitivity analyses can help to confirm the robustness of the results and mitigate the impact of "Splitting sigmas".

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