A linear transformation 
is hyperbolic if none of its eigenvalues
has modulus 1. This means that 
can be written as a direct sum
of two 
-invariant
subspaces 
and 
(where 
stands for stable and 
for unstable) such that there exist constants 
, 
, and 
with
 |  |  |
(1)
|
 |  |  |
(2)
|
for 
,
1, ....
