In general relativity , the peeling theorem describes the asymptotic behavior of the Weyl tensor as one goes to null infinity . Let
γ
{\displaystyle \gamma }
be a null geodesic in a spacetime
(
M
,
g
a
b
)
{\displaystyle (M,g_{ab})}
from a point p to null infinity, with affine parameter
λ
{\displaystyle \lambda }
. Then the theorem states that, as
λ
{\displaystyle \lambda }
tends to infinity:
C
a
b
c
d
=
C
a
b
c
d
(
1
)
λ
+
C
a
b
c
d
(
2
)
λ
2
+
C
a
b
c
d
(
3
)
λ
3
+
C
a
b
c
d
(
4
)
λ
4
+
O
(
1
λ
5
)
{\displaystyle C_{abcd}={\frac {C_{abcd}^{(1)}}{\lambda }}+{\frac {C_{abcd}^{(2)}}{\lambda ^{2}}}+{\frac {C_{abcd}^{(3)}}{\lambda ^{3}}}+{\frac {C_{abcd}^{(4)}}{\lambda ^{4}}}+O\left({\frac {1}{\lambda ^{5}}}\right)}
where
C
a
b
c
d
{\displaystyle C_{abcd}}
is the Weyl tensor, and abstract index notation is used. Moreover, in the Petrov classification ,
C
a
b
c
d
(
1
)
{\displaystyle C_{abcd}^{(1)}}
is type N,
C
a
b
c
d
(
2
)
{\displaystyle C_{abcd}^{(2)}}
is type III,
C
a
b
c
d
(
3
)
{\displaystyle C_{abcd}^{(3)}}
is type II (or II-II) and
C
a
b
c
d
(
4
)
{\displaystyle C_{abcd}^{(4)}}
is type I.