On Hadamard square roots of unity

A series all of whose coefficients have unit modulus is called an Hadamard square root of unity. We investigate and partially characterize the algebra ic Hadamard square roots of unity. The investigation makes use of a result about the asymptotic behavior of the coefficients of algebraic series and t he Weyl-von Neumann theorem. (C) 2000 Elsevier Science B.V. All rights rese rved.