  We address the question as to why, in the semiclassical limit, classically
chaotic systems generically exhibit universal quantum spectral statistics
coincident with those of Random Matrix Theory. To do so, we use a semiclassical
resummation formalism that explicitly preserves the unitarity of the quantum
time evolution by incorporating duality relations between short and long
classical orbits. This allows us to obtain both the non-oscillatory and the
oscillatory contributions to spectral correlation functions within a unified
framework, thus overcoming a significant problem in previous approaches. In
addition, our results extend beyond the universal regime to describe the
system-specific approach to the semiclassical limit.
