101. CMB 2008 (vol 51 pp. 100)
 Petkov, Vesselin

Dynamical Zeta Function for Several Strictly Convex Obstacles
The behavior of the dynamical zeta function $Z_D(s)$ related to
several strictly convex disjoint obstacles is similar to that of the
inverse $Q(s) = \frac{1}{\zeta(s)}$ of the Riemann zeta function
$\zeta(s)$. Let $\Pi(s)$ be the series obtained from $Z_D(s)$ summing
only over primitive periodic rays. In this paper we examine the
analytic singularities of $Z_D(s)$ and $\Pi(s)$ close to the line $\Re
s = s_2$, where $s_2$ is the abscissa of absolute convergence of the
series obtained by the second iterations of the primitive periodic
rays. We show that at least one of the functions $Z_D(s), \Pi(s)$
has a singularity at $s = s_2$.
Keywords:dynamical zeta function, periodic rays Categories:11M36, 58J50 

102. CMB 2008 (vol 51 pp. 134)
103. CMB 2007 (vol 50 pp. 594)
 Laubie, François

Ramification des groupes abÃ©liens d'automorphismes des corps $\mathbb F_q(\!(X)\!)$
Soit $q$ une puissance d'un nombre premier
$p$. Dans cette note on \'etablit la g\'en\'eralisation suivante
d'un th\'eor\`eme de Wintenberger : tout sousgroupe ab\'elien
ferm\'e du groupe des $\mathbb F_q$auto\morphismes continus du corps
des s\'eries formelles $\mathbb F_q(\!(X)\!)$ muni de sa filtration
de ramification est un groupe filtr\'e isomorphe au groupe de Galois
d'une extension ab\'elienne d'un corps local {\`a} corps
r\'esiduel $\mathbb F_q$, filtr\'e par les groupes de ramification
de l'extension en num\'erotation inf\'erieure.
Category:11S15 

104. CMB 2007 (vol 50 pp. 486)
105. CMB 2007 (vol 50 pp. 334)
106. CMB 2007 (vol 50 pp. 399)
 Komornik, Vilmos; Loreti, Paola

Expansions in Complex Bases
Beginning with a seminal paper of R\'enyi, expansions in noninteger real bases have been widely
studied in the last
forty years. They turned out to be relevant in
various domains of mathematics, such as the theory of finite
automata, number
theory, fractals or dynamical systems.
Several results were extended by Dar\'oczy and K\'atai
for expansions
in complex bases. We introduce an adaptation of the socalled greedy
algorithm to the complex case, and we
generalize one of their main theorems.
Keywords:noninteger bases, greedy expansions, betaexpansions Categories:11A67, 11A63, 11B85 

107. CMB 2007 (vol 50 pp. 409)
108. CMB 2007 (vol 50 pp. 215)
 Kloosterman, Remke

Elliptic $K3$ Surfaces with Geometric MordellWeil Rank $15$
We prove that the elliptic surface
$y^2=x^3+2(t^8+14t^4+1)x+4t^2(t^8+6t^4+1)$ has geometric MordellWeil
rank $15$. This completes a list of Kuwata, who gave explicit examples
of elliptic $K3$surfaces with geometric MordellWeil ranks
$0,1,\dots, 14, 16, 17, 18$.
Categories:14J27, 14J28, 11G05 

109. CMB 2007 (vol 50 pp. 196)
 Fernández, Julio; González, Josep; Lario, JoanC.

Plane Quartic Twists of $X(5,3)$
Given an odd surjective Galois representation $\varrho\from \G_\Q\to\PGL_2(\F_3)$ and a
positive integer~$N$, there exists a twisted modular curve $X(N,3)_\varrho$
defined over $\Q$ whose rational points classify the quadratic $\Q$curves of degree $N$
realizing~$\varrho$. This paper gives a method to provide an explicit plane quartic model for
this curve in the genusthree case $N=5$.
Categories:11F03, 11F80, 14G05 

110. CMB 2007 (vol 50 pp. 191)
 Drungilas, Paulius; Dubickas, Artūras

Every Real Algebraic Integer Is a Difference of Two Mahler Measures
We prove that every real
algebraic integer $\alpha$ is expressible by a
difference of two Mahler measures of integer polynomials.
Moreover, these polynomials can be chosen in such a way that they
both have the same degree as that of $\alpha$, say
$d$, one of these two polynomials is irreducible and
another has an irreducible factor of degree $d$, so
that $\alpha=M(P)bM(Q)$ with irreducible polynomials
$P, Q\in \mathbb Z[X]$ of degree $d$ and a
positive integer $b$. Finally, if $d \leqslant 3$, then one can take $b=1$.
Keywords:Mahler measures, Pisot numbers, Pell equation, $abc$conjecture Categories:11R04, 11R06, 11R09, 11R33, 11D09 

111. CMB 2007 (vol 50 pp. 234)
 Kuo, Wentang

A Remark on a Modular Analogue of the SatoTate Conjecture
The original SatoTate Conjecture concerns the angle distribution
of the eigenvalues arising from nonCM elliptic curves. In this paper,
we formulate a modular analogue of the SatoTate Conjecture and prove
that the angles arising from nonCM holomorphic Hecke
eigenforms with nontrivial central characters are not distributed
with respect to the SateTate measure
for nonCM elliptic curves. Furthermore, under a reasonable conjecture,
we prove that the expected distribution is uniform.
Keywords:$L$functions, Elliptic curves, SatoTate Categories:11F03, 11F25 

112. CMB 2007 (vol 50 pp. 313)
 Tzermias, Pavlos

On CauchyLiouvilleMirimanoff Polynomials
Let $p$ be a prime greater than or equal to 17 and
congruent to
2 modulo 3. We use results of Beukers and Helou on
CauchyLiouvilleMirimanoff
polynomials to show that
the intersection of the Fermat curve of degree $p$ with the
line $X+Y=Z$ in the projective plane
contains no algebraic points of degree
$d$ with $3 \leq d \leq 11$.
We prove a result on
the roots of these polynomials and show that, experimentally,
they seem to satisfy
the conditions of a mild extension of
an irreducibility theorem of P\'{o}lya and Szeg\"{o}.
These conditions are \emph{conjecturally}
also necessary for irreducibility.
Categories:11G30, 11R09, 12D05, 12E10 

113. CMB 2007 (vol 50 pp. 284)
 McIntosh, Richard J.

Second Order Mock Theta Functions
In his last letter to Hardy, Ramanujan
defined 17 functions $F(q)$, where $q<1$. He called them mock theta
functions, because as $q$ radially approaches any point $e^{2\pi ir}$
($r$ rational), there is a theta function $F_r(q)$ with $F(q)F_r(q)=O(1)$.
In this paper we establish the relationship between two families of mock
theta functions.
Keywords:$q$series, mock theta function, Mordell integral Categories:11B65, 33D15 

114. CMB 2007 (vol 50 pp. 158)
 Tipu, Vicentiu

A Note on Giuga's Conjecture
Let $G(X)$ denote the number of positive composite integers $n$
satisfying $\sum_{j=1}^{n1}j^{n1}\equiv 1 \tmod{n}$.
Then $G(X)\ll X^{1/2}\log X$ for sufficiently large $X$.
Category:11A51 

115. CMB 2007 (vol 50 pp. 71)
 Gurak, S.

Polynomials for Kloosterman Sums
Fix an integer $m>1$, and set $\zeta_{m}=\exp(2\pi i/m)$. Let ${\bar x}$
denote the multiplicative inverse of $x$ modulo $m$. The Kloosterman
sums $R(d)=\sum_{x} \zeta_{m}^{x + d{\bar x}}$, $1 \leq d \leq
m$, $(d,m)=1$,
satisfy the polynomial
$$f_{m}(x) = \prod_{d} (xR(d)) = x^{\phi(m)} +c_{1}
x^{\phi(m)1} + \dots + c_{\phi(m)},$$
where the sum and product are taken over a complete system of reduced residues
modulo $m$. Here we give a natural factorization of $f_{m}(x)$, namely,
$$ f_{m}(x) = \prod_{\sigma} f_{m}^{(\sigma)}(x),$$
where $\sigma$ runs through the square classes of the group ${\bf Z}_{m}^{*}$
of reduced residues modulo $m$. Questions concerning the explicit
determination of the factors $f_{m}^{(\sigma)}(x)$ (or at least their
beginning coefficients), their reducibility over the rational field
${\bf Q}$ and duplication among the factors are studied. The treatment
is similar to what has been done for period polynomials for finite
fields.
Categories:11L05, 11T24 

116. CMB 2007 (vol 50 pp. 11)
 Borwein, David; Borwein, Jonathan

van der Pol Expansions of LSeries
We provide concise series representations for various
Lseries integrals. Different techniques are needed below and above
the abscissa of absolute convergence of the underlying Lseries.
Keywords:Dirichlet series integrals, Hurwitz zeta functions, Plancherel theorems, Lseries Categories:11M35, 11M41, 30B50 

117. CMB 2006 (vol 49 pp. 578)
118. CMB 2006 (vol 49 pp. 560)
 Luijk, Ronald van

A K3 Surface Associated With Certain Integral Matrices Having Integral Eigenvalues
In this article we will show that there are infinitely many
symmetric, integral $3 \times 3$ matrices, with zeros on the
diagonal, whose eigenvalues are all integral. We will do this by
proving that the rational points on a certain nonKummer, singular
K3 surface
are dense. We will also compute the entire NÃ©ronSeveri group of
this surface and find all low degree curves on it.
Keywords:symmetric matrices, eigenvalues, elliptic surfaces, K3 surfaces, NÃ©ronSeveri group, rational curves, Diophantine equations, arithmetic geometry, algebraic geometry, number theory Categories:14G05, 14J28, 11D41 

119. CMB 2006 (vol 49 pp. 526)
 Choi, So Young

The Values of Modular Functions and Modular Forms
Let $\Gamma_0$ be a Fuchsian group of the first kind of genus zero
and $\Gamma$ be a subgroup of $\Gamma_0$
of finite index of genus zero. We find universal recursive
relations giving the $q_{r}$series coefficients of
$j_0$ by using those of the $q_{h_{s}}$series of $j$, where $j$ is
the canonical Hauptmodul for $\Gamma$ and $j_0$ is a Hauptmodul
for $\Gamma_0$ without zeros on the complex upper half plane
$\mathfrak{H}$ (here $q_{\ell} := e^{2 \pi i z / \ell}$). We find universal recursive formulas for
$q$series coefficients of any modular form on
$\Gamma_0^{+}(p)$ in terms of those of the canonical Hauptmodul $j_p^{+}$.
Categories:10D12, 11F11 

120. CMB 2006 (vol 49 pp. 481)
 Browkin, J.; Brzeziński, J.

On Sequences of Squares with Constant Second Differences
The aim of this paper is to study sequences of integers
for which the second differences between their squares are
constant. We show that there are infinitely many nontrivial
monotone sextuples having this property and discuss some related
problems.
Keywords:sequence of squares, second difference, elliptic curve Categories:11B83, 11Y85, 11D09 

121. CMB 2006 (vol 49 pp. 428)
 Lee, Min Ho

VectorValued Modular Forms of Weight Two Associated With JacobiLike Forms
We construct vectorvalued modular forms of weight 2 associated to
Jacobilike forms with respect to a symmetric tensor representation of
$\G$ by using the method of Kuga and Shimura as well as the
correspondence between Jacobilike forms and sequences of modular forms.
As an application, we obtain vectorvalued modular forms determined by
theta functions and by pseudodifferential operators.
Categories:11F11, 11F50 

122. CMB 2006 (vol 49 pp. 448)
123. CMB 2006 (vol 49 pp. 472)
124. CMB 2006 (vol 49 pp. 296)
 Sch"utt, Matthias

On the Modularity of Three CalabiYau Threefolds With Bad Reduction at 11
This paper investigates the modularity of three
nonrigid CalabiYau threefolds with bad reduction at 11. They are
constructed as fibre products of rational elliptic surfaces,
involving the modular elliptic surface of level 5. Their middle
$\ell$adic cohomology groups are shown to split into
twodimensional pieces, all but one of which can be interpreted in
terms of elliptic curves. The remaining pieces are associated to
newforms of weight 4 and level 22 or 55, respectively. For this
purpose, we develop a method by Serre to compare the corresponding
twodimensional 2adic Galois representations with uneven trace.
Eventually this method is also applied to a self fibre product of
the Hessepencil, relating it to a newform of weight 4 and level
27.
Categories:14J32, 11F11, 11F23, 20C12 

125. CMB 2006 (vol 49 pp. 247)