Classical Field Theory without Force

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SUMMARY

The discussion centers on the formulation of Classical Field Theory without invoking force, particularly in the context of General Relativity (GR) and Electromagnetism (E&M). Participants reference key works, including Jackson's "Classical Electrodynamics" and the Kaluza-Klein mechanism, which posits a fifth dimension to unify E&M and gravity. The conversation highlights the challenges of creating a field theory devoid of forces, emphasizing the Lorentz force's role and the implications of spacetime curvature. The consensus indicates that while alternative approaches exist, they often revert to force-based concepts.

PREREQUISITES
  • Understanding of General Relativity (GR)
  • Familiarity with Electromagnetism (E&M) principles
  • Knowledge of the Lorentz force equation
  • Basic concepts of Kaluza-Klein theory
NEXT STEPS
  • Study Jackson's "Classical Electrodynamics" for insights on relativistic dynamics
  • Explore the Kaluza-Klein mechanism and its implications for unifying forces
  • Research the role of spacetime curvature in GR and its effects on charged and uncharged matter
  • Investigate alternative formulations of E&M that do not rely on force concepts
USEFUL FOR

Physicists, theoretical researchers, and graduate students interested in advanced topics in field theory, particularly those exploring the intersection of electromagnetism and general relativity.

  • #31
Ben Niehoff said:
I'm sorry, this line of reasoning is totally wrong, and reaches a completely wrong conclusion. I'm not sure where you got this from, but it is clear you do not understand what 'd' is and how to apply it. Sounds like you should do some more basic reading.

You keep saying this sort of thing, and I appreciate it greatly. Can you be more specific in what you find erronious?

What do you recommend for more basic reading?

Point 3. Could you please answer me about how you arrived at d(A^G) = dA^G - A^dG?
 
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  • #32
Phrak said:
You keep saying this sort of thing, and I appreciate it greatly. Can you be more specific in what you find erronious?

What do you recommend for more basic reading?

Point 3. Could you please answer me about how you arrived at d(A^G) = dA^G - A^dG?

Hey Phrak if you still need to know the general product rule for differential forms is: given an n - form \Psi and an m - form \Phi
d(\Psi \wedge \Phi) = d\Psi \wedge \Phi + (-1)^{n}\Psi \wedge d\Phi
If you want to prove it then just work with the general equation for the wedge product of two differential forms and the general equation for the exterior derivative of a differential form.
 
  • #33
WannabeNewton said:
Hey Phrak if you still need to know the general product rule for differential forms is: given an n - form \Psi and an m - form \Phi
d(\Psi \wedge \Phi) = d\Psi \wedge \Phi + (-1)^{n}\Psi \wedge d\Phi
If you want to prove it then just work with the general equation for the wedge product of two differential forms and the general equation for the exterior derivative of a differential form.

Thanks for adding your thoughts, Wannabe N. Nice handle.

Your equation is

d(\Psi \wedge \Phi) = d\Psi \wedge \Phi + (-1)^{n}\Psi \wedge d\Phi \ .​
If the roles of \Psi and \Phi are reversed we have

d(\Phi \wedge \Psi) = d\Phi \wedge \Psi + (-1)^{m}\Phi \wedge d\Psi \ .​
This is an equally true statement; all this has done is to arbitrarily relabel free variables.

Commuting the wege product in each term and negating gives

d(\Psi \wedge \Phi) = \Psi \wedge d\Phi + (-1)^{m}d\Psi \wedge \Phi \ .​
Realigning terms to make comparison with your equation easy,
d(\Psi \wedge \Phi) = (-1)^{m}d\Psi \wedge \Phi \ + \Psi \wedge d\Phi.​
Your equation seems only to work when n and m are both even.
 
  • #34
Phrak said:
Commuting the wege product in each term and negating gives
d(\Psi \wedge \Phi) = \Psi \wedge d\Phi + (-1)^{m}d\Psi \wedge \Phi \ .

You cannot do that! And the formula works for any positive integers n and m.
One mistake is, let \Psi be a m form and \Phi a n form, then
\Psi\wedge \Phi = (-1)^{mn}\Phi\wedge\Psi.​

If you google "differential geometry lecture notes", or "differential forms lecture notes", then you will find many very good and free notes. A very nice and pedagogic book on these topics is "Gauge Fields, Knots and Gravity" by John Baez and Javier P Muniain.
 
  • #35
element4 said:
You cannot do that!
Thank's for the correction.
 

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