The Exponential Congruence Symbol

Abstract: In this work, we study the generalized k-th power symbol (a/n)_k and present a comprehensive collection of its algebraic properties. The results are classified according to their dependence on the three main parameters a, n, and k. In particular, we discuss multiplicativity, inversion, power compatibility, and invariance modulo n with respect to the parameter a. For n, we examine factorization properties, behavior on prime powers, orthogonality relations, and Kummer splitting criteria. Regarding k, we include specialization to classical symbols, k-th reciprocity laws, relations between orders, and embedding into roots of unity. Moreover, we extend the existing theory by providing new essential results, including additive behavior under characters, Mobius filtering, compatibility with Carmichael and Euler functions, and connections with Dirichlet L-series. Finally, we analyze the case where a, n, and k are primes and present mixed results that generalize classical reciprocity laws, Frobenius automorphisms, and Sato-Tate distributions. These results unify and extend previous studies on k-th power symbols and offer a foundation for further arithmetic, algebraic, and analytic investigations.