Theory and Examples of Generalised Prime Systems By Faez Ali AL-Maamori Thesis submitted for the degree of Doctor of Philosophy March 2013 Abstract A generalised prime system P is a sequence of positive reals p1, p2,p3,… satisfying 1 < p1 ≤ p2 ≤ … ≤ pn ≤ …and for which pn → ∞ as n → ∞. The {pn} called generalised primes (or Beurling primes) with the products p1a1. P2a2…pkak (where k ∈ N and a1,a1, … ak ∈ N ∪ {0} forming the generalised integers (or Beurling integers). In this thesis we study the generalised (or Beurling) prime systems and we examine the behaviour of the generalised prime and integer counting functions 𝜋𝜌(𝑥) and 𝑁P(x) and their relation to each other, including the Beurling zeta function 𝜁𝜌(s). Speci cally, we study a problem discussed by Diamond (see [7]) which is to determine the best possible in NP(x) = x + O(xe�c(log x) for some _ > 0; given that _P(x) = li(x) + O(xe�(log x)_); _ 2 (0; 1): We obtain the result that _ _ _: We study the connection between the asymptotic behaviour (as x ! 1) of the g-integer counting function NP(x) (or rather of NP(x) � ax ) and the size of Beurling zeta function _P(_ +it) with _ near 1 (as t ! 1). We show in the _rst section how assumptions on the growth of _P(s) imply estimates on the error term of NP(x), while in the second half we _nd the region where _P(_ + it) = O(tc); for some c > 0, if we assume that we have a bound for the error term of NP(x). Finally we apply these results to _nd O and results for a speci_c example. ); for some > 0; given that P(x) = li(x) + O(xe�(log x) ); 2 (0; 1): We obtain the result that