Every Hecke character of K satisfying (1.1) and (1.2) is actually a quadratic twist of a canonical Hecke character (see Section 2 for a precise description of these characters and which fields have them). Let L(s, χ) denote the Hecke L-function of χ, and Λ(s, χ) its completion; Λ(s, χ) satisfies the functional equation Λ(s, χ) = W (χ)Λ(2 − s, χ), where W (χ) = ±1 is the root number. If χ is a c...

A k-decomposition (G1, . . . , Gk) of a graph G is a partition of its edge set to form k spanning subgraphs G1, . . . , Gk. The classical theorem of Nordhaus and Gaddum bounds χ(G1) + χ(G2) and χ(G1)χ(G2) over all 2-decompositions of Kn. For a graph parameter p, let p(k;G) denote the maximum of ∑k i=1 p(Gi) over all k-decompositions of the graph G. The clique number ω, chromatic number χ, list ...

We obtain upper bounds for mixed exponential sums of the type S(χ, f, pm) = ∑pm x=1 χ(x)epm (ax n+bx) where pm is a prime power with m ≥ 2 and χ is a multiplicative character (mod pm). If χ is primitive or p (a, b) then we obtain |S(χ, f, pm)| ≤ 2np 2 3 . If χ is of conductor p and p (a, b) then we get the stronger bound |S(χ, f, pm)| ≤ npm/2.

Given a non-principal Dirichlet character χ (mod q), an important problem in number theory is to obtain good estimates for the size of L(1, χ). The best bounds known give that q−ǫ ≪ǫ |L(1, χ)| ≪ log q, while assuming the Generalized Riemann Hypothesis, J.E. Littlewood showed that 1/ log log q ≪ |L(1, χ)| ≪ log log q. Littlewood’s result reflects the true range of the size of |L(1, χ)| as it is ...