Strong persistence is a common phenomenon that has been documented not only in the levels but also in the volatility of many time series. The class of doubly fractional models is extended to include the possibility of long memory in cyclical (non-zero) frequencies in both the levels and the...

Strong cyclical persistence is a common phenomenon that has been documented not only in the levels but also in the volatility of many time series, specially in astronomical or business cycle data. The class of doubly fractional models is extended to include the possibility of long memory in...

The aim of this paper is to identify whether the GARCH or the SV based models provide the best goodness of fit to financial time-series data. To investigate the issue, three different formulations for each type (i.e., the standard model, the fat-tailed model, and the asymmetric model) are...