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Box 20.3 (The Legendre recurrence of U ( m ) A
in terms of U A , index set
A 1 ,A 2 ,...,A m− 1 ,A m
∈{
1 , 2
}
( Legendre 1806 )).
A
A 1 A 2
U A 1 U A 2 (geodesic , ( 20.42 )) ,
U A =
(20.55)
U A =
A
A 1 A 2
U A 3 U A 2 U A 1 +2 A
A
A 3 A 4
U A 2 U A 3 U A 4 ,
=
A 1 A 2
A 3
U (4) A =
(20.56)
A
A 1 A 2
, A 3 A 4 U A 4 U A 3 U A 2 U A 1
=
+3 A
, A 3
A 3
A 4 A 5
U A 1 U A 2 U A 4 U A 5
A 1 A 2
+ A
, A 3
A 1
A 4 A 5
A A 2 U A 3 U A 4 U A 5
A 1 A 2
+6 A
A 1
A 3 A 4
A 3
A 5 A 6
U A 2 U A 4 U A 5 U A 6 , etc .
A 1 A 2
If we replace U ( m ) A in the Taylor expansion ( 20.54 ) by means of the Legendre recurrence of
Box 20.3 ,wehavesolved the initial value problem of the geodesic ( 20.42 ) in terms of power series
U A 0 ,U A 0 U A 0 ,U A 0 U A 0 U A 0 etc. generating an exponential map , in particular
U A ( S ) =
(20.57)
= U 0 + SU 0 + S 2 A A 1 ,A 2 U A 0 U A 0 + ...
n
S m A A 1 A 2 ...A m U A 0 U A 0 ...U A 0 .
+ lim
n→∞
m =3
With respect to the first chart , part of the minimal atlas of E
A 1 ,A 2 , namely the orthogonal coor-
, we transform U 0 via
dinates
{
L, B
}
x
y
S G 22
L 0 = U 1 0 =
S G 11 ,B 0 = U 2 0 =
(20.58)
into (Riemann) normal coordinates {x, y} (inverse Riemann mapping, inverse Riemann cha-cha-
cha). Accordingly, we succeed to represent th e Ta ylor series ( 20. 54 ) i n terms of (Riemann) normal
coordinates {x, y} , in particular, x 1 := x/ G 11 and x 2 := y/ G 22
 
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