��������һ��Լ�����÷���ģ��,
����ΥԼǿ�ȶ���Ϊ��������, ���Ǹ���L'evy����.
�ø��ʷ����õ���ΥԼʱ��ֲ��Ľ������ʽ. ���øý������ʽ,
�����˸����÷���ģ���µ�����ΥԼ����(Credit Default
Swaps)�ı���ʽ�Ķ��۹�ʽ.

For a reduced form model of credit risk,
we use Cox process whose intensity process is a subordinator process
to define the default time of the company. We derive closed forms of
the distribution of the company's default time. We also derive the
fair price of the defaultable zero coupon bond and the credit spread
of the credit default swaps.