1) dynamic panel: panel cointegration, cross sectional dependence, bootstrap.....
2) nonlinear dynamics: time series, multivariate, nonlinear ECM(STAR, THR, MS models......), nonlinear transformation of I(1)
3) long memory I(d) process with 0<d<1, robustness of unit root and cointegration test( against nonlinearity), long run variance(kernal, bandwith selection)......
4) nonparametric test of cointegration, nonparametric nonlinear......... continuous stochastic models of second moments
5) local time of brownian motion and its estimation
there are some nontrivial problems for the theoretical foundation of nonlinearity...................
Peter and Park's work confront the nontrivial problem of identification, it requires knowledge of analysis.................
Factor models are vary hot issues..
copula, stochasitc correlation are the beloved of finance people