Heston
Model variance as a mean-reverting square-root diffusion.
Build the mental model first.
Heston becomes useful once its observable quote, state variables and governing convention are kept separate. Build the mental model before selecting the numerical method.
Model variance as a mean-reverting square-root diffusion.
Now make it exact.
Notation and units
Decimal rates and volatilities, year-fraction time and continuous compounding unless stated otherwise.
Every model has a price.
Educational conventions are stated explicitly and may simplify market quotation or settlement details.
Rates are continuously compounded unless the section says otherwise.
Inputs are deterministic in the base model.
“An unstated convention is a future reconciliation break.”— THEQUANTBATEMAN
Why a quant cares.
Heston appears in pricing, scenario analysis, risk aggregation or hedge design. Production use requires explicit units, calendars, interpolation and data lineage.
The hedge has opinions.
Start with the quote convention, then ask which EQ risk survives the hedge. A number without its convention is merely well-dressed ambiguity.
Ask Bateman about this model →