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where
x 1 ) 2 P 2 +
···
is a regular matrix function of x and 1 is a unit matrix. By virtue of equality,
P ( x )= 1 +( x
x 1 ) P 1 +( x
T 0 = 0
( 0 is a zero matrix) in the expansion of the exponent into a power series all
the powers above the first turn into zero and we obtain
U ( x )= 1 +( x
···
x 1 ) 2 P 2 +
x 1 ) P 1 +( x
×
( 1 + T 0 ln( x
x 1 )) .
(4.59)
Calculations shown in Chapter 6 yield
= D 1 k A ( x 1 ) R 1 ( x )+ D 2 S 1 ( x )+ R 1 ,
b ( x )
B 0
(4.60a)
S 2 ( x )+ R 2
k A ( x 1 )
,
ξ x ( x )= D 1 R 2 ( x )+ D 2
(4.60b)
1
x
x 1 + S 3 ( x )+ R 3 .
ik y
k A ( x 1 )
ξ y ( x )= D 1 ik y R 3 ( x )+ D 2
(4.60c)
Here we denote R i = k y R i ( x )ln[ k y ( x
x 1 )] ,i =1 , 2 , 3. Functions R n ( x )and
S n ( x )havetheform
x 1 ) 2
x 1 ) 2
R 1 ( x )= ( x
( x
R 2 ( x )=1+ k y
+
···
,
+
···
,
2
4
x 1 ) 2
4
R 3 = x
x 1
( x
k y
+
···
,
S 1 ( x )=1
+
···
,
2
1+
( x
k y k A ( x 1 )
2( k A ( x 1 ) ) 2
k A ( x 1 )
2 k A ( x 1 )
S 2 ( x )=
x 1 )+
···
,S 3 ( x )=
+
···
.
The coecients D 1 and D 2 are arbitrary constants which can be found
from the boundary conditions. Relations connecting electric E and magnetic
b fields with displacement ξ
reduce for a plane wave
exp ( iωt
i kr )to
(see 4.32)
E x
B 0
= i ω
E y
B 0
i ω
c ξ y ,
=
c ξ x ,
b x
B 0
b y
B 0
b B 0
= ik ξ x ,
=
ik ξ y ,
=
·
ξ
.
The main singularity of the field near the resonance point x 1 can be found
without determining the coecients D 1 and D 2 . Note that at x
x 1 pertur-
bations of the longitudinal magnetic field b tend to a constant b 0 and have a
logarithmic singularity
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