On the Liouville function at polynomial arguments

: Teräväinen, Joni

Publisher: JOHNS HOPKINS UNIV PRESS

: BALTIMORE

: 2024

: American Journal of Mathematics

: AMERICAN JOURNAL OF MATHEMATICS

: AM J MATH

: 146

: 4

: 1115

: 1167

: 54

: 0002-9327

: 1080-6377

DOI: https://doi.org/10.1353/ajm.2024.a932436(external)

: https://muse.jhu.edu/article/932436(external)

: https://arxiv.org/pdf/2010.07924(external)

: https://arxiv.org/abs/2010.07924(external)

Let lambda denote the Liouville function. A problem posed by Chowla and by Cassaigne-Ferenczi-Mauduit-Rivat-Sarkozy asks to show that if P(x) is an element of Z[x], then the sequence lambda(P(n)) changes sign infinitely often, assuming only that P(x) is not the square of another polynomial. We show that the sequence lambda(P(n)) indeed changes sign infinitely often, provided that either (i) P factorizes into linear factors over the rationals; or (ii) P is a reducible cubic polynomial; or (iii) P factorizes into a product of any number of quadratics of a certain type; or (iv) P is any polynomial not belonging to an exceptional set of density zero. Concerning (i), we prove more generally that the partial sums of g(P(n)) for g a bounded multiplicative function exhibit nontrivial cancellation under necessary and sufficient conditions on g . This establishes a "99% version" of Elliott's conjecture for multiplicative functions taking values in the roots of unity of some order. Part (iv) also generalizes to the setting of g(P(n)) and provides a multiplicative function analogue of a recent result of Skorobogatov and Sofos on almost all polynomials attaining a prime value.