# Contents

## Idea

The field strength of the electromagnetic field.

## Details

Over Minkowski space $\mathbb{R}^{4}$:

$A = \phi \mathbf{d}t + A_1 \mathbf{d}x^1 + A_2 \mathbf{d}x^2 + A_3 \mathbf{d}x^3$

then field strength is the de Rham differential

$F \coloneqq \mathbf{d}A = E_1 \mathbf{d}t \wedge \mathbf{d}x^1 + E_2 \mathbf{d}t \wedge \mathbf{d}x^2 + E_3 \mathbf{d}t \wedge \mathbf{d}x^3 + B_1 \mathbf{d}x^2 \wedge \mathbf{d}x^3 + B_2 \mathbf{d}x^3 \wedge \mathbf{d}x^1 + B_3 \mathbf{d}x^1 \wedge \mathbf{d}x^2$

with

$E_i = \frac{\partial \phi}{\partial x^i}$

the electric field strength

and

$B_1 = \frac{\partial A_2}{\partial x^3} - \frac{\partial A_3}{\partial x^2}$

etc

the magnetic field strength.

The field strength is closed, $\mathbf{d} F = 0$

this are the first 2 of 4 Maxwell equations

Created on November 9, 2012 17:34:27 by Urs Schreiber (80.187.201.44)