CM newforms with rational coefficients

The problem of summation of Fourier series in finite form is formulated in the weak sense, which allows one to consider this problem uniformly both for classically convergent and for divergent series. For series with polynomial Fourier coefficients \(a_n, b_n \in \mathbb{R}[n]\), it is proved that the sum of a Fourier series can be represented as a linear combination of 1, \(\delta(x)\), \(\cot \frac{x}{2}\) and their derivatives. It is shown that this representation can be found in a finite number of steps. For series with rational Fourier coefficients \(a_n, b_n \in \mathbb{R}(n)\), it is shown that the sum of such a series is always a solution of a linear differential equation with constant coefficients whose right-hand side is a linear combination of 1, \(\delta(x)\), \(\cot \frac{x}{2}\) and their derivatives. Thus, the issue of summing a Fourier series with rational coefficients is reduced to the classical problem of the theory of integration in elementary functions.

Generalised Kummer constructions and Weil restrictions

Let f be a newform of weight k ≥ 3 with Fourier coefficients in a number field K . We show that the universal deformation ring of the mod λ Galois representation associated to f is unobstructed, and thus isomorphic to a power series ring in three variables over the Witt vectors, for all but finitely many primes λ of K . We give an explicit bound on such λ for the 6 known cusp forms of level 1, trivial character, and rational Fourier coefficients. We also prove a somewhat weaker result for weight 2.

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

The purpose of this note is to prove that under certain hypotheses, the graded ring of integral automorphic forms, with respect to an arithmetic group operating On a tube domain, is generated as a graded algebra over the complex numbers by a finite number of automorphic forms having rational integral Fourier coefficients. The result, which seems to have some potential numbertheoretic interest, was inspired by notes of M. Eichler [8, esp. Satz 49] and by questions raised in correspondence with that author and with I. I. Pyatetskii-Shapiro. One should also note the similarity of ideas here with those used in the proof of Satz D of [9]. We wish to remark, furthermore, that in most cases lengthy computations will be needed to verify the applicability of our theorem here, which should therefore be regarded more as a technical lemma than as a substantial contribution in itself. As in [2], let ~ denote a (hermitian) symmetric tube domain, let F be a discrete, arithmetically defined subgroup of the group of all holomorphic automorphisms of ~ , and assume that ~ has a zerodimensional rational boundary component Fo, which we take to be the zero-dimensional rational boundary component of ~ at infinity as in [2]. Let

An explicit formula for the mean value of $\vert L(1,\chi )\vert ^2$ is known, where $\chi $ runs over all odd primitive Dirichlet characters of prime conductors p. Bounds on the relative class number of the cyclotomic field ${\mathbb Q}(\zeta _p)$ follow. Lately, the authors obtained that the mean value of $\vert L(1,\chi )\vert ^2$ is asymptotic to $\pi ^2/6$ , where $\chi $ runs over all odd primitive Dirichlet characters of prime conductors $p\equiv 1\ \ \pmod {2d}$ which are trivial on a subgroup H of odd order d of the multiplicative group $({\mathbb Z}/p{\mathbb Z})^*$ , provided that $d\ll \frac {\log p}{\log \log p}$ . Bounds on the relative class number of the subfield of degree $\frac {p-1}{2d}$ of the cyclotomic field ${\mathbb Q}(\zeta _p)$ follow. Here, for a given integer $d_0>1$ , we consider the same questions for the nonprimitive odd Dirichlet characters $\chi '$ modulo $d_0p$ induced by the odd primitive characters $\chi $ modulo p. We obtain new estimates for Dedekind sums and deduce that the mean value of $\vert L(1,\chi ')\vert ^2$ is asymptotic to $\frac {\pi ^2}{6}\prod _{q\mid d_0}\left (1-\frac {1}{q^2}\right )$ , where $\chi $ runs over all odd primitive Dirichlet characters of prime conductors p which are trivial on a subgroup H of odd order $d\ll \frac {\log p}{\log \log p}$ . As a consequence, we improve the previous bounds on the relative class number of the subfield of degree $\frac {p-1}{2d}$ of the cyclotomic field ${\mathbb Q}(\zeta _p)$ . Moreover, we give a method to obtain explicit formulas and use Mersenne primes to show that our restriction on d is essentially sharp.

On the mean square average of special values of L-functions

We give explicit constants κ such that if χ is a real non-principal Dirichlet character for which L(1,χ)≤κ, then Chowla's hypothesis is not satisfied and we cannot use Chowla's method for proving that L(s,χ)>0 for s>0. These constants are larger than the previous ones κ=1−log2=0.306… and κ=0.367… we obtained elsewhere.

In this paper, a method is described for computing the Dirichlet L -functions and their zeros on the line Rs =1/2 Many functions with real and complex characters and moduli up to 163 have been computed. The results have been deposited in the Royal Society Depository for Unpublished Mathematical Tables, no. 75. From these results it can be shown that the Riemann hypothesis is true in the range of the calculations.

Estimating averages of Dirichlet convolutions $1\ast \unicode[STIX]{x1D712}$, for some real Dirichlet character $\unicode[STIX]{x1D712}$ of fixed modulus, over the sparse set of values of binary forms defined over $\mathbb{Z}$ has been the focus of extensive investigations in recent years, with spectacular applications to Manin’s conjecture for Châtelet surfaces. We introduce a far-reaching generalisation of this problem, in particular replacing $\unicode[STIX]{x1D712}$ by Jacobi symbols with both arguments having varying size, possibly tending to infinity. The main results of this paper provide asymptotic estimates and lower bounds of the expected order of magnitude for the corresponding averages. All of this is performed over arbitrary number fields by adapting a technique of Daniel specific to $1\ast 1$. This is the first time that divisor sums over values of binary forms are asymptotically evaluated over any number field other than $\mathbb{Q}$. Our work is a key step in the proof, given in subsequent work, of the lower bound predicted by Manin’s conjecture for all del Pezzo surfaces over all number fields, under mild assumptions on the Picard number.

Riesz-type criteria and theta transformation analogues

Let [Formula: see text] be a real and non-principal Dirichlet character, [Formula: see text] its Dirichlet [Formula: see text]-function and let [Formula: see text] be a generic prime number. We prove the following result: If for some [Formula: see text] the partial sums [Formula: see text] change sign only for a finite number of integers [Formula: see text], then there exists [Formula: see text] such that [Formula: see text] has no zeros in the half plane [Formula: see text].

For a half integral weight modular form f we study the signs of the Fourier coefficients a(n). If f is a Hecke eigenform of level N with real Nebentypus character, and t is a fixed square-free positive integer with a(t) 6= 0, we show that for all but finitely many primes p the sequence (a(tp))m has infinitely many signs changes. Moreover, we prove similar (partly conditional) results for arbitrary cusp forms f which are not necessarily Hecke eigenforms.

In this paper we study the Fourier coefficients of theta functions attached to Dirichlet characters at cusps other than infinity. The method is based on expressing them in terms of explicit elements of the adelic Schwartz space and studying the action of the adelic metaplectic group on these elements. We derive explicit formulae for the Fourier coefficients at all cusps. For the sake of simplicity, some restrictions are placed on the Dirichlet characters considered.

This paper presents a new probabilistie primality test. Upon termination the test outputs "composite" or "prime", along with a short proof of correctness, which can be verified in deterministic polynomial time. The test is different from the tests of Miller [M], Solovay-Strassen [SSI, and Rabin [R] in that its assertions of primality are certain, rather than being correct with high probability or dependent on an unproven assumption.