n
nicefa.
Advanced Proof

The Heston Stochastic Volatility Model: Capturing the Leverage Effect

Students often struggle with the Feller condition, 2κθ>σ2 2\kappa\theta > \sigma^2 . This ensures the variance vt v_t remains strictly positive. If this condition is violated, the variance can touch zero, leading to mathematical instabilities that suggest the model is failing to constrain the physical reality of volatility.
Institutional Reference: Advanced Stochastic Processes
View Full Proof →