Arithmetic Poisson summation formulas
We formulate Poisson summation with periodic weights in forms adapted to arithmetic sums (arithmetic Poisson summation formulas, APSF), in scalar, polynomial-congruence and vector-divisibility versions, extending Berndt's arithmetic Poisson formula. We use APSF as a common framework to rederive Ramanujan's formula for $ζ(2m+1)$ and its character analogues due to Katayama and Berndt-Straub, the functional equations of $ζ$, of Dirichlet's beta function and of Estermann's function, and the exponents of Tolev and Chen-Wang for power-free values of $x^2+y^2+1$ and $x^2+y^2+z^2+k$. It also gives reciprocity laws with Kelvin-function kernels for Lambert series twisted by a Dirichlet character over imaginary quadratic fields of arbitrary class number; asymptotic formulas with error terms for $r$-free values of $x_1^2+\cdots+x_n^2+k$, with Gaussian-weighted versions and the meromorphic continuation of the associated Dirichlet series; an argument of Terras, relating two-dimensional Bessel series for all odd zeta values and even Dirichlet beta values; and a Gaussian representation of a Mersenne-Fermat prime detector.