“The following problem arises immediately. If ε is a positive quantity, to find a polynomial of the form
f(x) = xr + a1 xr-1 + … + ar
where the a's are integers, such that the absolute value of the product of those roots of f which lie outside the unit circle, lies between 1 and 1 + ε.
“This problem, in interest in itself, is especially important for our purposes. Whether or not the problem has a solution for ε < 0.176 we do not know.” — Derrick Henry Lehmer, 1933.
Mahler's measure of a polynomial f is defined to be the absolute value of the product of those roots of f which lie outside the unit disk, multiplied by the absolute value of the coefficient of the leading term of f. We denote it M(f).
Lehmer's problem, sometimes called Lehmer's question, or Lehmer's conjecture, asks if there exists a constant C > 1 such that every polynomial f with integer coefficients and M(f) > 1 has M(f) ≥ C.
Lehmer added the following remark in his 1933 paper (using Ω to denote the measure):
“We have not made an examination of all 10th degree symmetric polynomials, but a rather intensive search has failed to reveal a better polynomial than
x10 + x9 − x7 − x6 − x5 − x4 − x3 + x + 1, Ω = 1.176280818.
“All efforts to find a better equation of degree 12 and 14 have been unsuccessful.”
Despite extensive searches, Lehmer's polynomial remains the world champion.
This page summarizes what is known today about Lehmer's problem.
It includes descriptions of algorithms, histories of searches performed,
and various lists of polynomials with small measure.
Please write if you have comments or contributions!
Last modified June 30, 2011.
Talks on Lehmer's Problem and Mahler's Measure
Department of Mathematics
Davidson College
Davidson, North Carolina 28035-6996
mimossinghoff "at" davidson "dot" edu