Partitions of primes by Chebyshev polynomials

Partitions of the set of primes are introduced based on the Chebyshev polynomials at rationals. The prime densities of all such partitions are established. Euler's Criterion for $SL(2,\mathbb Q)$ is formulated, which is the bridge between the algebra of Chebyshev polynomials and number-theoretic properties of the partitions. It is shown how to obtain in this way some of the classical theory of Lucas sequences. A hidden symmetry of the problem is revealed by the new language. As an application number-theoretic properties of simple dynamical systems (rotations and certain interval maps) are discussed.