In reviewing some basic GR (just to keep my old brain sharp), i was looking at the Einstein notation cinvention and was a bit confused. I see how you do the dot product of say:(adsbygoogle = window.adsbygoogle || []).push({});

e^{i}.e_{j}= δ^{i}_{j}

(i.e. 1 or 0)

But then the book I'm reading talks about e_{i}.e_{j}or e^{i}.e^{j}. Isn't that just the square of e^{i}or e_{i}? I thought the choice of index notation was irrelevant as it just goes over 1, 2, 3?

Or am I missing something basic? (first time in my life!)

If it is, why not just call it square?

Thanks!

Sterling

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# Simple GR Einstein Notation Question

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