May 30th, 2007, 3:47 am
Hi,Not sure between points (2) and (3). Are you saying dw(t,i) and dS(t,i) has a correlation(possibly option implied) for ith stock, dS(t,i) and dS(t,j) has a correlation (maybe historical) and dw(t,i) and dw(t,j) are uncorrelated?.Either ways my naive guess would be that multidim heston would produce a lower expectation. I mean when correlation is being played, I would think you would like a dynamic/time varying correlation matrix. Because you have problems of positive definiteness and bounded values [-1,1] for corr matrix I think people try to take a dynamic covariance matrix.One such type of a covar matrix is one where the matrix is driven by a diffusion process with the probabilities prescribed by a wishart distribution. The dynamics of the corr matrix process are then got from dynamics of the covar matrix through an ito manipuation. This matrix is able to meet the above constraints (under some conditions).Thanks