Higher dimensional FTC in electrostatics: Mathematically rigorous or not?

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Discussion Overview

The discussion revolves around the mathematical rigor of applying the Fundamental Theorem of Calculus (FTC) in the context of electrostatics, particularly in higher dimensions. Participants explore the implications of charge distributions in separate volumes and the integration of forces between them.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant presents a scenario involving two non-overlapping volumes filled with electric charge and questions the mathematical rigor of the implication relating force and charge distributions.
  • Another participant notes the relevance of Stoke's theorem when considering integrals in higher dimensions, suggesting a connection to the discussion on the FTC.
  • Clarification is sought regarding the acronym FTC, with some participants initially misunderstanding it as referring to the Federal Trade Commission instead of the Fundamental Theorem of Calculus.
  • There is an acknowledgment that defining acronyms is important for clarity in discussions.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the mathematical rigor of the FTC in this context, and there are competing views regarding the application of the theorem in higher dimensions.

Contextual Notes

Some assumptions regarding the continuity of charge density and the nature of the integrals over volumes and surfaces remain unaddressed, leading to potential limitations in the discussion.

oliverkahn
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I have two volumes ##V## and ##V'## in space such that:

1. ##∄## point ##P## ##\ni## ##[P \in V ∧ P\in V']##

2. ##V## is filled with electric charge ##q##

3. ##\rho = \dfrac{dq}{dV}## varies continuously in ##V##

4. ##V'## is filled with electric charge ##q'##

5. ##\rho' = \dfrac{dq'}{dV'}## varies continuously in ##V'##

Let ##r## be the distance between a point ##P_1 \in V## and a point ##P_2 \in V'##

In electrostatics, we use the implication:

##\displaystyle \dfrac{d^2\vec{F}}{dq\ dq'}=k\dfrac{\hat{r}}{r^2} \implies \vec{F}=k\int_q \int_{q'}\dfrac{\hat{r}}{r^2} dq'\ dq##

Does this implication has any mathematically rigor?

NOTE: I know:

##G(x)## is differentiable on interval ##[a,b]##

##\land## ##g(x)## is Riemann integrable function in interval ##[a,b]##

##\land## ##\dfrac{d\ G(x)}{dx} = g(x)## in interval ##(a,b)##

##\implies \displaystyle G(b)-G(a) = \int^b_a g(x) dx##

But I don't see why this works for integral over a volume, integral over a surface, etc...
 
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@oliverkahn - what does FTC stand for? Some of us mentors are confused.. I'm one of them.
 
oliverkahn said:
But I don't see why this works for integral over a volume, integral over a surface, etc...
In case the dimension is higher than one, it is called Stoke's theorem.
 
jim mcnamara said:
@oliverkahn - what does FTC stand for? Some of us mentors are confused.. I'm one of them.
Fundamental Theorem of Calculus
 
oliverkahn said:
Fundamental Theorem of Calculus
Rats. I had "Federal Trade Commission" in the Mentor pool. Oh well...

(It's always best to define your acronyms when you use them when they may be non-obvious...) :smile:
 
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And assume they are never obvious.
 
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