,
,
instead of 1, 2, 3, and we shall reserve the numeral indices 1, 2, 3, 4 for the four-dimensional space-time continuum.
If there exists with respect to
only a magnetic field,
, but no electric field,
,
,
instead of 1, 2, 3, and we shall reserve the numeral indices 1, 2, 3, 4 for the four-dimensional space-time continuum.
If there exists with respect to
only a magnetic field,
, but no electric field,