ON TIME-REVERSIBILITY OF MULTIVARIATE LINEAR PROCESSES

We study the time-reversibility of multivariate linear processes, introduc- ing a necessary and sucien t condition related to linear transforms of the multivari- ate linear process. Conditions analogous to Cheng's for univariate non-Gaussian linear processes are also explored; these are in terms of the noise distribution and the model parameters. The exploration results in an easily veriable set of neces- sary and sucien t conditions for a multivariate non-Gaussian linear process driven by a univariate noise, leaving the case of multivariate noise as a challenging open problem.