We consider the distribution of argζ(σ+it) on fixed lines σ>21, and in particular the density d(σ)=T→+∞lim2T1∣{t∈[−T,+T]:∣argζ(σ+it)∣>π/2}∣, and the closely
related density d−(σ)=T→+∞lim2T1∣{t∈[−T,+T]:ℜζ(σ+it)<0}∣. Using classical results of
Bohr and Jessen, we obtain an explicit expression for the characteristic
function ψσ(x) associated with argζ(σ+it). We give
explicit expressions for d(σ) and d−(σ) in terms of
ψσ(x). Finally, we give a practical algorithm for evaluating these
expressions to obtain accurate numerical values of d(σ) and
d−(σ).Comment: 22 pages, 3 tables. To appear in Proceedings of the International
Number Theory Conference in Memory of Alf van der Poorten (Newcastle,
Australia, 2011