Dirac equation is always written with indices. Is there any way to write it down without any indices ABSTRACT or not, and without coordinates,basis vectors etc..?
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2Always? $/ !!!\partial$ . – Cosmas Zachos Sep 17 '19 at 16:35
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How can you have a differential equation for a function on spacetime without having any coordinates to express where you are in spacetime? – G. Smith Sep 17 '19 at 16:37
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No, you don’t need indices. Just write it out using $t,x,y,z$ derivatives. – G. Smith Sep 17 '19 at 16:38
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3There is, although doing it carefully requires introduction of spinor bundles. See https://ncatlab.org/nlab/show/Dirac+operator for example. – Peter Kravchuk Sep 17 '19 at 16:45
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This is still in component form exactly the opposite of what I want. It's not about being invariant under component of frame transformations , it's about being completely coordinateless as I specified in the question. – Kugutsu-o Sep 18 '19 at 08:18
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G smith_ using vectors not coordinates – Kugutsu-o Sep 19 '19 at 13:38
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Writing out $\gamma^\mu \partial_\mu$ is really no different than writing anything that looks like an inner product (for example, the Laplacian). If you're concerned that the indices don't make the frame-independence obvious, then just write it as a four-vector dot product: $$ (i\gamma\cdot\partial - m)\psi = 0. $$
I'm not saying that this notation is usual, or even that you will find it anywhere, but it seems no different to me than writing, say, $\nabla \times \nabla f = 0$ or $\nabla \cdot \nabla \phi = -\rho$.
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Ok so why don't you write it down exactly as you did the last line if it's all the same.. – Kugutsu-o Sep 18 '19 at 07:56