tokens: When the simulator is based on differential equations , the link between Gaussian Processes ( GP ) and linear stochastic differential equations ( SDE ) Poggio1990 , Steinke2008 , Albert2012 , Sarkka2013 , Gonzalez2014 , Solin2014 , permits the creation of GP based emulators that include knowledge about the simulator dynamics ; these are called mechanistic emulators ( MEMs ) .