Single-Particle Electrodynamics - Assassination Science

All addition operations for arbitrary objects are assumed to be commutative,
without need for this to be explicitly noted. No assumptions about
commutativity of multiplication operations are made in the general case.
A.6.1
C-numbers and q-numbers
Quantities that commute with all other quantities are referred to as c-numbers.
Any quantity that is not a c-number is a q-number.
A.6.2
Commutators and anticommutators
The commutator of two quantities A and B is defined to be AB − BA, and
is denoted by brackets, thus:
[A, B] ≡ AB − BA.
(A.32)
The anticommutator of two quantities A and B is defined to be AB + BA,
and is denoted by braces, thus:
{A, B} ≡ AB + BA.
(A.33)
Commutators and anticommutators may be collectively referred to as
permutators. Quantities that are commutated or anticommutated are collectively
referred to as being permutated.
Indices may also be permutated:
and
A [α B β] ≡ A α B β − A β B α
A {α B β} ≡ A α B β + A β B α .
(A.34)
(A.35)
The permutated indices may be separated by an arbitrary number of intervening
factors, and may be repeated for identical indices within the one
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