riskless rate การใช้

The equation states that over any infinitesimal time interval the loss from theta and the gain from the gamma term offset each other, so that the result is a return at the riskless rate.
Where E is the expectations operator, pj is the end-of-period random yield on the jth asset, pm is the end-of-period random yield on the market portfolio and r is one plus the riskless rate of return.
Where the dependent variable, ( r _ j-r _ f ) _ t is the asset return in excess of the riskless rate, the two intercepts are a _ j ^ + and a _ j ^-, for the up-market and down-market regime respectively, and \ beta _ j ^ + ( r _ m ^ +-r _ f ) _ t is the product of the up-market beta and the up-market excess return, and similarly \ beta _ j ^-( r _ m ^-- r _ f ) _ t is the product of the down-market beta and the down-market excess return . a _ j ^ +, \ beta _ j ^ +, a _ j ^-, and \ beta _ j ^-are the estimated parameters for up-market and down-market days, respectively; r _ m ^ + = r _ m on days the market index did not decline and r _ m ^-= r _ m on days it did; D is a dummy variable, which takes the value of 1 when the market index daily return is non-negative and zero otherwise . The final term, \ epsilon _ t, reflects the idiosyncratic information not proportional to either the up-market or down-market excess returns .