Geometric Brownian motion 228
One realization of a geometric Brownian motion
()
[][][][][][][][][]()
()
dt
S
dt
S
N
dS
dt
dt
N
dS S
dt
dW
V
dW
dt
dW
V
dt
V
dW
dt
V
dS S
V
dt
dt
dW
E
dt
dW
E
dt
E
dW
dt
E
dS S
E
dt
N
dW
where
dW
dt
dS S
t
t
t
t t
t
t
t
t
t t
t
t
t
t t
t
t
t t
2 ² , ~ & ² , ~
²
0
²
0
,
cov
2
0
, 0
~
,
σ
μ
σ
μ
σ σ σ μ σ μ σ μ
μ μ σ μ σ μ σ
σ μ
μ
⇒
= + + = + + = + =
⎤ ⎥ ⎦
⎡ ⎢ ⎣
= + = + = + = + =
⎤ ⎥ ⎦
⎡ ⎢ ⎣
+
=
Derivative securities: Options - Black-Scholes model