How to Derive d^* Without Using the Hodge Star Operator?

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SUMMARY

The discussion focuses on deriving the adjoint of the exterior derivative d^* on a Riemannian manifold without utilizing the Hodge star operator. Participants emphasize the importance of the inner product defined by the Riemannian metric g and reference key texts such as John Baes' "Knots, Gauge Theory and Gravity" and R.W.R. Darling's "Differential Forms and Connections." The conversation highlights the challenge of expressing d^* through the canonical inner product directly, without relying on Hodge duality, and seeks alternative methodologies for achieving this derivation.

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  • Understanding of Riemannian manifolds and their metrics
  • Familiarity with differential forms and exterior derivatives
  • Knowledge of Hodge duality and its implications in differential geometry
  • Proficiency in mathematical notation and inner product definitions
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HenryGomes
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Usually the adjoint to the exterior derivative d^* on a Riemannian manifold is derived using the inner product
\langle\langle\lambda_1,\lambda_2\rangle\rangle:=\int_M\langle\lambda_1,\lambda_2\rangle\mbox{vol}=\int_M\lambda_1\wedge*\lambda_2
where \lambda are p-forms and * is the Hodge duality operator taking p-forms to (n-p)-forms which is defined by the above equation where \langle\cdot,\cdot\rangle is the canonical inner product induced on p-forms by the Riemannian metric g (it is just the tensor p-product of the inverse metric).
It is quite easy to derive d^*=*d*. But does anyone know how to do this without using Hodge star operator, through the g-induced inner product directly?
 
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what text are you referencing?
 
Any good differential geometry book should have this. One I like, which is for physicist's is John Baes' "Knots, Gauge Theory and Gravity". You might also want to check out Bleecker's " Variational Principles in Gauge Theories". I re-read the post and it seemed a bit badly written. So just to spell out what I meant:
The Hodge star is defined by:
\langle \lambda_1,\lambda_2\rangle vol=\lambda_1\wedge*\lambda_2
Find the adjoint of d without using Hodge star, just the canonically induced metric \langle\cdot,\cdot\rangle
 
thanks, Henry.

I have R.W.R. Darling's "Differential Forms and Connections". Formal. Not written for physicists. And a 1985 dover reprint, Dominic G. B. Edelen, "Applied Exterior Calculus". Neither one have I read yet.

Perhaps you could tell me if either of these texts might be worth trying.

I don't want to be misleading. I find differential forms fascinating in their application to physics. Sadly, I'm not capable of responding to your past three posts, as yet, but I would surely like to get to that point. From what I've seen over the past 6 weeks, Hurkyl seems to talk of differential forms with some authority. You might try buttonholing him for some input.

-deCraig
 
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Silly question -- if you want to express * d * without the Hodge stars, what's wrong with simply replacing them with a formula that calculates them?


Or... maybe your question is more fundamental? You call it the adjoint, so I assume

\langle d^* f, g \rangle = \langle f, dg \rangle?

Was that what you wanted? Or maybe something like d^*f is the transpose of the tangent multi-vector \langle f, d \_\_\_ \rangle?
 
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Because it is not really the answer I am looking for, but to apply a different method to obtain adjoints when we do not have the Hodge star. Thanks for the answer!
 

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