均衡模型是对即时短期利率做动态假设，模拟它的走势
无套利模型是根据市场上债券价格，抽取其蕴含的利率动态

你们知道单因子模型中的Sita（t）是如何确定的吗

the term structure is spot rates at all maturities. Models that take the initial term structure implied by market prices are called arbitragefree models. A different approach, however, is to start with assumptions about the interest rate process and about the risk premium demanded by the market for bearing interest rate risk and then derive the risk-neutral process. Models of this sort do not necessarily match the initial term structure and are called equilibrium models.