A Hilbert space of Dirichlet series is
obtained by considering the Dirichlet series f(s) = ∑n=1∞ann−s that
satisfy ∑n=0∞|an|2< +∞. These series converge in the half plane
Res > and define a functions
that are locally L2 on the boundary Res = . An analog of Carleson’s celebrated
convergence theorem is obtained: Each such Dirichlet series
converges almost everywhere on the critical line Res = . To each Dirichlet series of the above type
corresponds a “trigonometric” series ∑n=1∞anχ(n), where
χ is a multiplicative character
from the positive integers to the unit circle. The space of
characters is naturally identified with the
infinite-dimensional torus T∞, where each dimension comes from a
a prime number. The second analog of Carleson’s theorem
reads: The above “trigonometric” series converges for
almost all characters χ.