Simultaneous non-vanishing and sign changes of Fourier coefficients of modular forms

Abstract

In this paper, we give some results on simultaneous non-vanishing and simultaneous sign-changes for the Fourier coefficients of two modular forms. More precisely, given two modular forms [Formula: see text] and [Formula: see text] with Fourier coefficients [Formula: see text] and [Formula: see text] respectively, we consider the following questions: existence of infinitely many primes [Formula: see text] such that [Formula: see text]; simultaneous non-vanishing in the short intervals and in arithmetic progressions; simultaneous sign changes in short intervals.