x
0
(t)
T
ˆ
A(t
0
)
µ
i
x
0
(t)
|µ
i
| ≤ 1, i = 1, 2, . . . , N
+1
N
X
i=1
µ
i
= Sp
ˆ
M
T
,
N
Y
i=1
µ
i
= Det
ˆ
M
T
.
λ
i
=
1
T
ln |µ
i
|.
λ
i
≤ 0 λ
i
> 0
x
0
(t)
k ω
j
j = 1, 2, . . . , k
x
0
(t) = x
0
(ϕ
1
(t), ϕ
2
(t), . . . , ϕ
k
(t))
= x
0
(ϕ
1
(t) + 2πm, ϕ
2
(t) + 2πm, . . . , ϕ
k
(t) + 2πm),
m ϕ
j
(t) = ω
j
t, j = 1, 2, . . . , k
ˆ
A(t)