Salem numbers as Mahler measures of nonreciprocal units by Artūras Dubickas (Vilnius) 1. Introduction. Recall that for a polynomial f (x) = a(x − α 1). .. (x − α n) ∈ C[x], where a = 0, its Mahler measure is defined by M (f) := |a| n j=1 max{1, |α j |}. If f (x) = (x − α 1). .. (x − α n) ∈ Q[x] is irreducible over the field Q, we denote by K f its splitting field Q(α 1 ,. .. , α n) and by G f = Gal(K f /Q) its Galois group. Also, the polynomial f is called reciprocal if the set {α 1 ,. .. , α n } of its roots is equal to {α −1 1 ,. .. , α −1 n }, i.e. f (x) = ±x n f (x −1), and nonreciprocal otherwise. A root α > 1 of a monic irreducible polynomial f in Z[x] of degree 2n ≥ 4 is called a Salem number if f is reciprocal and has 2n − 2 roots on the unit circle |z| = 1. Let L 0 be the set of all possible Mahler measures of nonreciprocal (but not necessarily irreducible) polynomials in Z[x]. Various aspects of the set of all Mahler measures L := {M (f) : f ∈ Z[x]} and of its subset of nonreciprocal measures L 0 := {M (f) : f ∈ Z[x], f nonreciprocal} have been investigated in the papers of Adler and Marcus [1], Boyd [2], [3], [4], Dixon and Dubickas [6], Dubickas [8], and Schinzel [12]. One of the problems from the recent BIRS workshop "The Geometry, Algebra and Analysis of Algebraic Numbers" held in 2015 in Banff (Canada) suggested by David Boyd, 7(c), is the following: • Does L 0 contain any Salem numbers?