On nontrivial zeros for the Ramanujan zeta function

The Hardy hypothesis, as an analogue to the Riemann hypothesis for the Riemann zeta function, is a conjecture proposed by Hardy in 1940, that all of the nontrivial zeros for the Ramanujan zeta function have a real part equal to 6. In this paper, we propose the power series expansion for the entire Ramanujan zeta function using the work of Mordell. Then, we suggest an alternative infinite product for the entire Ramanujan zeta function derived from the work of Conrey and Ghosh. We also establish the class of the entire Ramanujan zeta function related to the functional equation coming from Wilton. Motivated by the work of Lekkerkerker, we prove an conjecture due to Bruijn that all of the zeros of the Ramanujan Xi function are nonzero real numbers. From theory of the entire functions, we also prove that the Hardy hypothesis is true.