Classical Field Theory without Force

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Discussion Overview

The discussion centers around the concept of classical field theory without the notion of force, exploring its implications and potential formulations. Participants examine the relationship between classical electrodynamics and general relativity, as well as the challenges of creating a field theory that does not rely on forces.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that the idea of classical field theory without force may relate to general relativity (GR), but others argue that it does not directly equate to GR, as it seems to rehash the Lorentz force.
  • There is a discussion about the equation mx''=q(E+vxB), with some claiming it is neither a field equation nor relativistic, while others propose that replacing mx'' with p' could make it relativistic.
  • One participant mentions that the acceleration of charged particles depends on the charge-to-mass ratio, contrasting it with GR where acceleration is independent of object composition.
  • Some participants reference the Kaluza-Klein mechanism as a way to unify electromagnetism and gravity, suggesting that it allows for an equivalence principle that could lead to a formulation of E&M without forces.
  • There are mentions of various articles and resources that explore the formulation of electromagnetic fields in curved spacetime, indicating ongoing exploration in this area.
  • Concerns are raised about the lack of an equivalence principle in electromagnetism, complicating the construction of a field theory without forces.
  • One participant expresses interest in the quantization of wave solutions in the context of Kaluza-Klein theory, noting potential implications for particle masses and properties.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of formulating a classical field theory without force. While some explore potential approaches, there is no consensus on whether such a theory can be successfully developed or what it would entail.

Contextual Notes

Limitations include unresolved mathematical steps and the dependence on definitions of force and curvature in the context of electromagnetism and gravity.

  • #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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