Determining cusp forms by central values of Rankin-Selberg L-functions

Let g be a fixed normalized Hecke-Maass cusp form for SL(2,Z) associated to the Laplace eigenvalue . We show that g is uniquely determined by the central values of the family for k sufficiently large, where Hk(1) denotes a Hecke basis of the space of holomorphic cusp forms for SL(2,Z).     

On some functional relations between Mordell-Tornheim double L-functions and Dirichlet L-functions

In the past decade, many relation formulas for the multiple zeta values, further for the multiple L-values at positive integers have been discovered. Recently Matsumoto suggested that it is important to reveal whether those relations are valid only at integer points, or valid also at other values. Indeed the famous Euler formula for ζ(2k) can be regarded as a part of the functional equation of ζ(s). In this paper, we give certain analytic functional relations between the Mordell-Tornheim double L-functions and the Dirichlet L-functions of conductor 3 and 4. These can be regarded as continuous generalizations of the known discrete relations between the Mordell-Tornheim L-values and the Dirichlet L-values of conductor 3 and 4 at positive integers.     

Salem numbers and L-functions

Every Salem number is the exponential of a rational multiple of the derivative at s = 0 of an Artin L-function.     

L-functions of twisted Legendre curves

Let K be a global field of char p and let Fq be the algebraic closure of Fp in K. For an elliptic curve E/K with nonconstant j-invariant, the L-function L(T,E/K) is a polynomial in 1+T⋅Z[T]. For any N>1 invertible in K and finite subgroup T⊂E(K) of order N, we compute the mod N reduction of L(T,E/K) and determine an upper-bound for the order of vanishing at 1/q, the so-called analytic rank of E/K. We construct infinite families of curves of rank zero when q is an odd prime power such that for some odd prime ?. Our construction depends upon a construction of infinitely many twin-prime pairs (Λ,Λ−1) in Fq[Λ]×Fq[Λ]. We also construct infinitely many quadratic twists with minimal analytic rank, half of which have rank zero and half have (analytic) rank one. In both cases we bound the analytic rank by letting T≅Z/2⊕Z/2 and studying the mod-4 reduction of L(T,E/K).     

Self-approximation of Dirichlet L-functions

Let d be a real number, let s be in a fixed compact set of the strip 1/2<σ<1, and let L(s,χ) be the Dirichlet L-function. The hypothesis is that for any real number d there exist ‘many’ real numbers τ such that the shifts L(s+iτ,χ) and L(s+idτ,χ) are ‘near’ each other. If d is an algebraic irrational number then this was obtained by T. Nakamura. ?. Pańkowski solved the case then d is a transcendental number. We prove the case then d≠0 is a rational number. If d=0 then by B. Bagchi we know that the above hypothesis is equivalent to the Riemann hypothesis for the given Dirichlet L-function. We also consider a more general version of the above problem.     

Linnik-type problems for automorphic L-functions

Let m?2 be an integer, and π an irreducible unitary cuspidal representation for GLm(AQ), whose attached automorphic L-function is denoted by L(s,π). Let be the sequence of coefficients in the Dirichlet series expression of L(s,π) in the half-plane Rs>1. It is proved in this paper that, if π is such that the sequence is real, then there are infinitely many sign changes in the sequence , and the first sign change occurs at some , where Qπ is the conductor of π, and the implied constant depends only on m and ε. This generalizes the previous results for GL₂. A result of the same quality is also established for , the sequence of coefficients in the Dirichlet series expression of in the half-plane Rs>1.     

Special values of L-functions by a Siegel-Weil-Kudla-Rallis formula

We study the arithmeticity of special values of L-functions attached to cuspforms which are Hecke eigenfunctions on hermitian quaternion groups Sp^∗(m,0) which form a reductive dual pair with G=O^∗(4n). For f₁ and f₂ two cuspforms on H, consider their theta liftings θf₁ and θf₂ on G. Then we compute a Rankin-Selberg type integral and obtain an integral representation of the standard L-function:

G〈θf₁⋅Es,θf₂〉=H〈f₁,f₂〉⋅Lstd(f₁,s).     

The L-functions of twisted Witt extensions

The L-function of a non-degenerate twisted Witt extension is proved to be a polynomial. Its Newton polygon is proved to lie above the Hodge polygon of that extension. And the Newton polygons of the Gauss-Heilbronn sums are explicitly determined, generalizing the Stickelberger theorem.     

Explicit zero-free regions for Dirichlet L-functions

Let $\text{L}$_k(S) be the product of the ?(k) Dirichlet L-functions formed with characters modulo k. We prove the existence of explicit numerical zero-free regions for $\text{L}$_k(S). The first result is that $\text{L}$_k(S) has at most a single zero in the region {$\text{s: σ > 1 ?}\text{1}\text{(R}\text{log}\text{M)}\text{}}$, where R = 9.645908801 and M = max {k, k |t|, 10}. The only possible zero in this region is a simple real zero arising from an L-function formed with a real non-principal character. The second result is that if χ₁ and χ₂ are distinct real primitive characters modulo k₁ and k₂, respectively, and if β₁ is a zero of L(s, χ_i), i = 1, 2, then min $\text{{β}{}_1\text{, β}{}_2\text{} < 1 ?}\text{1}\text{(R}{}_1\text{log}\text{M}{}_1\text{)}$, where $\text{R}{}_1\text{=}\text{(5 ? √5)}\text{(15 ? 10√2)}$, and $\text{M}{}_1\text{=}\text{max}\text{{}\text{k}{}_1\text{k}{}_2\text{17}\text{, 13}}$.     

On L-functions of cyclotomic function fields

We study two criterions of cyclicity for divisor class groups of function fields, the first one involves Artin L-functions and the second one involves “affine” class groups. We show that, in general, these two criterions are not linked.     

Arakawa-Kaneko L-functions and generalized poly-Bernoulli polynomials

We introduce and investigate generalized poly-Bernoulli numbers and polynomials. We state and prove several properties satisfied by these polynomials. The generalized poly-Bernoulli numbers are algebraic numbers. We introduce and study the Arakawa-Kaneko L-functions. The non-positive integer values of the complex variable s of these L-functions are expressed rationally in terms of generalized poly-Bernoulli numbers and polynomials. Furthermore, we prove difference and Raabe?s type formulae for these L-functions.     

Integral mean values of modular L-functions

We consider the mean squares of L-functions associated to modular forms with respect to Hecke congruence subgroups, expressing the mean value as an inner product. This avoids the discussion of generalized additive divisor problems. As applications, we obtain asymptotic formulas for both weighted and unweighted mean squares.     

Euler numbers congruences and Dirichlet L-functions

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In this paper we apply Yamamoto's Theorem [Y. Yamamoto, Dirichlet series with periodic coefficients, in: Proc. Intern. Sympos. “Algebraic Number Theory”, Kyoto, 1976, JSPS, Tokyo, 1977, pp. 275-289] to find the residue modulo a prime power of the linear combination of Dirichlet L-function values L(s,χ) at positive integral arguments s such that s and χ are of the same parity, in terms of Euler numbers, whereby we obtain the finite expressions for short interval character sums. The results obtained generalize the previous results pertaining to the congruences modulo a prime power of the class numbers as the special case of s=1.

Video

For a video summary of this paper, please visit http://www.youtube.com/watch?v=_KAv4FCdVUs.     

The eighth moment of Dirichlet L-functions

We prove an asymptotic for the eighth moment of Dirichlet L-functions averaged over primitive characters χ modulo q  , over all moduli q?Q$q?Q$ and with a short average on the critical line, conditionally on GRH. We derive the analogous result for the fourth moment of Dirichlet twists of GL(2)$\mathit{GL}(2)$L-functions. Our results match the moment conjectures in the literature; in particular, the constant 24 024 appears as a factor in the leading order term of the eighth moment.     

On the behaviour of p-adic L-functions

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Let Lp(s,χ) denote a Leopoldt-Kubota p-adic L-function, where p>2 and χ is a nonprincipal even character of the first kind. The aim of this article is to study how the values assumed by this function depend on the Iwasawa λ-invariant associated to χ. Assuming that λ?p−1, it turns out that Lp(s,χ) behaves, in some sense, like a polynomial of degree λ. The results lead to congruences of a new type for (generalized) Bernoulli numbers.

Video

For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=5aaB1d6fZDs.     

Average values of L-functions in characteristic two

Gauss made two conjectures about average values of class numbers of orders in quadratic number fields, later on proven by Lipschitz and Siegel. A version for function fields of odd characteristic was established by Hoffstein and Rosen. In this paper, we extend their results to the case of even characteristic. More precisely, we obtain formulas of average values of L-functions associated to orders in quadratic function fields over a constant field of characteristic two, and then derive formulas of average class numbers of these orders.     

Central values of L-functions over CM fields

We prove an explicit formula for the central values of certain Rankin L-functions. These L-functions are the L-functions attached to Hilbert newforms over a totally real field F, twisted by unitary Hecke characters of a totally imaginary quadratic extension of F. This formula generalizes our former result on L-functions twisted by finite CM characters.     

Zeros of derivatives of sum of Dirichlet L-functions

A linear combination L(s) of two Dirichlet L-functions has infinitely many complex zeros in Res<0. In this note we prove an infinity of complex zeros of L(k)(s) in the same region.