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In the following section, we shall employ the material explained in Eqs.
(11-20) to analyze the field produced by a point charge with a relativistic
trajectory.
6.2.3 THE LI É NARD-WIECHERT FIELD
The solution of Eqs. (11f) and (11g) for a particle in arbitrary motion in
Minkowski space was obtained by Liénard and Wiechert; the correspond-
ing potential carries their names and is given by
(
)
r
b
1
r
q
=
charge / 4
πε
A
X
=
qw
v
,
(retarded potential),
(21a)
0
which is fundamental in everything that follows; by the use of Eq. (11a), it
is simple to calculate the associated Faraday tensor :
(
)
(21b)
2
2
F wUkUk wUk
=
=
×
rb
r
b
b
r
r
b
means the antisymmetric product. This notation is due to Lowry
[22] and will cause such expressions to be very compact. From Eqs. (11c)
and (21b), it is clear that
where
×
*
2
ab
,
(21c)
FqwUk
=−
ε
mn
mnab
therefore
,
F
=
0
(21d)
24
Fq
=−
2
<
0
2
1
In other words, the electric and magnetic fields generated by the charge
satisfy

EB
=
0
BE
<
,
(21e)
),
the invariant F tends to zero, which means that F is close to the null case
(type C ) far away from the charge.
With Eqs. (21d) and (20c) is valid; therefore, the Stachel theorem [2]
implies that Eq. (21b) can be reduced to Eq. (20b). This is easy to do be-
cause from Eqs. (4) and (5), the following relationships are available:
In consequence F is type B . Note that in the asymptotic region ( w
→∞
 
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