A terminological note on cyclotomic polynomials and Blaschke matrices

In a recent paper, Mertens and Ravn (2010) study the effects of anticipated fiscal policy shocks in a structural vector autoregressive model. The authors maintain that (i) the lag polynomial associated with news shocks is a cyclotomic polynomial and (ii) the matrix B(L) which transforms a nonfundamental MA representation into a fundamental one is a Blaschke matrix. Though the results in Mertens and Ravn (2010) are correct, we find that the terms 'cyclotomic' and 'Blaschke matrix' are misused.