The Wishart distribution has long been a useful tool for modeling covariance structures. According to Gyndikin’s theorem, the degrees of freedom (df) for a Wishart distribution can be any real number belonging to the Gyndikin set, either integer-valued or fractional. However, the fractional-df...

In stochastic volatility models, the unit root test on the time series of the unobserved log-volatilities may be performed by applying the commonly usedfrequentist unit root tests. For instance, augmented Dickey Fuller tests based on the log-squared meancorrected returns can be used. The...