Non-vanishing and Sign Changes of Hecke Eigenvalues for Siegel Cusp Forms of Genus Two

In this paper, we show that half of non-zero coefficients of the spinor zeta function of a Siegel cusp form of genus 2 are positive and half are negative. We also prove results concerning the non-vanishing in short intervals and strong cancellation among the coefficients evaluated at powers of a fixed prime. Our results rest on a Serre’s type density result established by Kowalski and Saha in the Appendix.