Classically developed as a tool for partial differential equations, the
analysis of operators known as pseudodifferential analysis is here
regarded as a possible help in questions of arithmetic. The operators
which make up the main subject of the book can be characterized in terms
of congruence arithmetic. They enjoy a Eulerian structure, and are
applied to the search for new conditions equivalent to the Riemann
hypothesis. These consist in the validity of certain parameter-dependent
estimates for a class of Hermitian forms of finite rank. The Littlewood
criterion, involving sums of Möbius coefficients, and the Weil so-called
explicit formula, which leads to his positivity criterion, fit within
this scheme, using in the first case Weyl's pseudodifferential calculus,
in the second case Fuchs'.
The book should be of interest to people looking for new possible
approaches to the Riemann hypothesis, also to new perspectives on
pseudodifferential analysis and on the way it combines with modular form
theory. Analysts will have no difficulty with the arithmetic aspects,
with which, save for very few exceptions, no previous acquaintance is
necessary.