1.2题，没有听懂，Y=0.34-0.55X，(1) X和Y分别是什么？题目说回归是用来估计long-term average correlation of the common stocks and the mean reverting rate. 那Y是long-term average correlation吗？X是mean reverting rate，还是average weekly correlation?
(2) 老师说mean reverting=55%，老师之前说St=a*u+(1-a)*St-1的式子里a*u的部分是mean reverting，那和Y=0.34-0.55X怎么对应啊？-0.55X对应a*u吗？a可以是负数吗？
