Recent content by Lapidus

Fμν = ∂μAν- ∂νAμ ∂μFμν = ∂2μAν - ∂ν(∂μAμ) = ∂2μAνWhy ∂ν(∂μAμ) and not ∂μ∂νAμ ? And why does ∂ν(∂μAμ) drop out? thank you

Why do I perceive "now" as a special moment compared to all the other moments in my life, past and present? Which physics equation, concept, theory accounts for one of the most human conscious experience, the perception that time flows, that the past becomes the present, that the present becomes...

For some strange reason I have not found this site before. Looks perfect! Thanks PAllen!

That looks very good and might be just what I wanted. I will check it out at my library on Monday! Thanks George!

Thanks so far for your answers. I am still interested in thoughts about the nature of time from physicists that go beyond the pure operational approach. Again: Does anybody know of papers, talks or chapter of books where trained physicists speculate about what time is (or might be) besides...

Repeating? You mean, repeating in time?

This I knew, too. But I wanted to know what a clock is. Can you explain it without time?

What is a clock? Can you define it without the concept of time?

There are quite some pop-sci books (by Greene, Smolin, Carroll and others) that deal with the "nature of time". Why does time appear to flow? Why is there a special moment, the "now"? Does simultaneity in SR imply a block universe? Why time-symmetric laws but a time-unsymmetric universe? Does...

Fantastic! Thanks Samalkhaiat! Kronecker Deltas from derivatives and indices swapping in the Levi-Civita. Got it. I must study a little tensor calculus..

Orodruin, I really appreciate your time and effort. I read carefully all your posts in this thread and the link you gave. But unfortunately, I still can not answer my initial question. Maybe I try somewhere else. Thank you!

L = aμ∂νaλ ∂L/∂aμ - ∂ν (∂L/∂(∂νaμ)) = ∂vaμ - ∂v ? I do not know what and how to differentiate in the second term. Also, I need to add two identical terms to get the factor two. But there is a minus sign.

I differentiate γεμνλaμ∂νaλ w.r.t. aμ and I get γεμνλ∂νaλ and γεμνλaμ∂νaλ w.r.t. ∂νaλ which gives γεμνλaμ. Thus γεμνλ∂νaλ - γεμνλaμ = 0 , which is not 2γεμνλ∂νaμ = 0.

I get the equation but without the 2 in front. I do not see how the 2 comes about. How to sum over the indices. I find the indices confusing. Hence my question.

Right. And a derivative in front of one a. Do I get one term from the RHS and one from the LHS of equation of motion and then I add them together?