1. CMB Online first
 Gu, Miao; Martin, Gregory George

Factorization tests and algorithms arising from counting modular forms and automorphic representations
A theorem of Gekeler compares the number of nonisomorphic automorphic
representations associated with the space of cusp forms of weight
$k$ on $\Gamma_0(N)$ to a simpler function of $k$ and $N$, showing
that the two are equal whenever $N$ is squarefree. We prove the
converse of this theorem (with one small exception), thus providing
a characterization of squarefree integers. We also establish
a similar characterization of prime numbers in terms of the number
of Hecke newforms of weight $k$ on $\Gamma_0(N)$.
It follows that a hypothetical fast algorithm for computing the
number of such automorphic representations for even a single
weight $k$ would yield a fast test for whether $N$ is squarefree.
We also show how to obtain bounds on the possible square divisors
of a number $N$ that has been found to not be squarefree via
this test, and we show how to probabilistically obtain
the complete factorization of the squarefull part of $N$ from
the number of such automorphic representations for two different
weights. If in addition we have the number of such Hecke newforms
for even a single weight $k$, then we show how to probabilistically
factor $N$ entirely.
All of these computations could be performed quickly in practice,
given the number(s) of automorphic representations and modular
forms as input.
Keywords:modular form, automorphic representation, squarefree number, primality testing, factorization algorithm Categories:11F70, 11N25, 11N60, 11Y05, 11Y16 

2. CMB 2017 (vol 61 pp. 376)
 Sebbar, Abdellah; AlShbeil, Isra

Elliptic Zeta Functions and Equivariant Functions
In this paper we establish a close connection between three
notions attached to a modular subgroup. Namely the set of weight
two meromorphic modular forms, the set of equivariant functions
on the upper halfplane commuting with the action of the modular
subgroup and the set of elliptic zeta functions generalizing
the Weierstrass zeta functions. In particular, we show that the
equivariant functions can be parameterized by modular objects
as well as by elliptic objects.
Keywords:modular form, equivariant function, elliptic zeta function Categories:11F12, 35Q15, 32L10 

3. CMB 2017 (vol 60 pp. 329)
 Le Fourn, Samuel

Nonvanishing of Central Values of $L$functions of Newforms in $S_2 (\Gamma_0 (dp^2))$ Twisted by Quadratic Characters
We prove that for $d \in \{ 2,3,5,7,13 \}$ and $K$ a quadratic
(or rational) field of discriminant $D$ and Dirichlet character
$\chi$, if a prime $p$ is large enough compared to $D$, there
is a newform $f \in S_2(\Gamma_0(dp^2))$ with sign $(+1)$ with
respect to the AtkinLehner involution $w_{p^2}$ such that $L(f
\otimes \chi,1) \neq 0$. This result is obtained through an estimate
of a weighted sum of twists of $L$functions which generalises
a result of Ellenberg. It relies on the approximate functional
equation for the $L$functions $L(f \otimes \chi, \cdot)$ and
a Petersson trace formula restricted to AtkinLehner eigenspaces.
An application of this nonvanishing theorem will be given in
terms of existence of rank zero quotients of some twisted jacobians,
which generalises a result of Darmon and Merel.
Keywords:nonvanishing of $L$functions of modular forms, Petersson trace formula, rank zero quotients of jacobians Categories:14J15, 11F67 

4. CMB 2014 (vol 57 pp. 485)
 Franc, Cameron; Mason, Geoffrey

Fourier Coefficients of Vectorvalued Modular Forms of Dimension $2$
We prove the following Theorem. Suppose that $F=(f_1, f_2)$ is a $2$dimensional vectorvalued modular form
on $\operatorname{SL}_2(\mathbb{Z})$ whose component functions $f_1, f_2$ have rational Fourier coefficients
with bounded denominators. Then $f_1$ and $f_2$ are classical modular forms on a congruence subgroup of the modular group.
Keywords:vectorvalued modular form, modular group, bounded denominators Categories:11F41, 11G99 

5. CMB 2013 (vol 57 pp. 845)
 Lei, Antonio

Factorisation of Twovariable $p$adic $L$functions
Let $f$ be a modular form which is nonordinary at $p$. Loeffler has
recently constructed four twovariable $p$adic $L$functions
associated to $f$. In the case where $a_p=0$, he showed that, as in
the onevariable case, Pollack's plus and minus splitting applies to
these new objects. In this article, we show that such a splitting can
be generalised to the case where $a_p\ne0$ using Sprung's logarithmic
matrix.
Keywords:modular forms, padic Lfunctions, supersingular primes Categories:11S40, 11S80 

6. CMB 2012 (vol 56 pp. 520)
 Elbasraoui, Abdelkrim; Sebbar, Abdellah

Equivariant Forms: Structure and Geometry
In this paper we study the notion of equivariant forms introduced in
the authors' previous works. In particular, we completely classify all the
equivariant forms for a subgroup of
$\operatorname{SL}_2(\mathbb{Z})$
by means of the crossratio, the weight
2 modular forms, the quasimodular forms, as well as differential forms
of a Riemann surface and sections of a canonical line bundle.
Keywords:equivariant forms, modular forms, Schwarz derivative, crossratio, differential forms Category:11F11 

7. CMB 2011 (vol 55 pp. 400)
 Sebbar, Abdellah; Sebbar, Ahmed

Eisenstein Series and Modular Differential Equations
The purpose of this paper is to solve various differential
equations having Eisenstein series as coefficients using various tools and techniques. The solutions
are given in terms of modular forms, modular functions, and
equivariant forms.
Keywords:differential equations, modular forms, Schwarz derivative, equivariant forms Categories:11F11, 34M05 

8. CMB 2005 (vol 48 pp. 180)
 Cynk, SÅ‚awomir; Meyer, Christian

Geometry and Arithmetic of Certain Double Octic CalabiYau Manifolds
We study CalabiYau manifolds constructed as double coverings of
$\mathbb{P}^3$ branched along an octic surface. We give a list of 87
examples corresponding to arrangements of eight planes defined over
$\mathbb{Q}$. The Hodge numbers are computed for all examples. There are
10 rigid CalabiYau manifolds and 14 families with $h^{1,2}=1$. The
modularity conjecture is verified for all the rigid examples.
Keywords:CalabiYau, double coverings, modular forms Categories:14G10, 14J32 
