The purpose of this paper is to prove that the common terms of linear recurrences $M(2a,-1,0,b)$ and $N(2c,-1,0,d)$ have at most $2$ common terms if $p=2$, and have at most three common terms if $p>2$ where $D$ and $p$ are fixed positive integers and $p$ is a prime, such that neither $D$ nor $D+p$ is perfect square, further $a,b,c,d$ are nonzero integers satisfying the equations $a^2-D{b}^2=1$ and $c^2-(D+p)d^2=1$.

Let G be a commutative algebraic group defined over a number field K that is disjoint over K from ${}_a$ and satisfies the condition of semistability. Consider a linear form l on the Lie algebra of G with algebraic coefficients and an algebraic point u in a p-adic neighbourhood of the origin with the condition that l does not vanish at u. We give a lower bound for the p-adic absolute value of l(u) which depends up to an effectively computable constant only on the height of the linear form, the height...

Hecke groups $H\left({\lambda }_q\right)$ are the discrete subgroups of $\mathrm{P}SL(2,ℝ)$ generated by $S\left(z\right)=-{(z+{\lambda }_q)}^{-1}$ and $T\left(z\right)=-\frac{1}{z}$. The commutator subgroup of $H$(${\lambda }_q)$, denoted by $H^{\text{'}}\left({\lambda }_q\right)$, is studied in [2]. It was shown that $H^{\text{'}}\left({\lambda }_q\right)$ is a free group of rank $q-1$. Here the extended Hecke groups $\overline{H}\left({\lambda }_q\right)$, obtained by adjoining $R_1\left(z\right)=1/\overline{z}$ to the generators of $H\left({\lambda }_q\right)$, are considered. The commutator subgroup of $\overline{H}\left({\lambda }_q\right)$ is shown to be a free product of two finite cyclic groups. Also it is interesting to note that while in the $H\left({\lambda }_q\right)$ case, the index of $H^{\text{'}}\left({\lambda }_q\right)$ is changed by $q$, in the case of $\overline{H}\left({\lambda }_q\right)$, this number is either 4 for...

Les variétés abéliennes principalement polarisées admettent un espace des modules grossier qu’on sait compactifier de plusieurs façons (compactification de Satake, compactifications toroïdales). Cependant, le problème s’est posé de construire une compactification “modulaire”en termes d’objets géométriques qui permettent de décrire les points du bord. On souhaite aussi compactifier l’application de Torelli qui à chaque courbe algébrique, projective et lisse, associe sa jacobienne. L’exposé présente...

Nous construisons la compactification minimale de certaines variétés modulaires de Siegel en leurs places de mauvaise réduction. Ces variétés paramètrent des schémas abéliens principalement polarisés munis d’une structure de niveau parahorique en un nombre premier $p$ et d’une structure de niveau auxilliaire  ; elles ont mauvaise réduction en $p$. Nous esquissons également une théorie arithmétique des formes modulaires de Siegel associées à ces variétés.

Soit $f$ un revêtement ramifié de ${𝐏}_1$ défini sur $\overline{𝐐}$. Lorsqu’on s’intéresse aux propriétés de rationalité de $f$ sur les les corps de nombres, on peut soit exiger que la base soit ${𝐏}_1$, soit l’autoriser à être une courbe de genre $0$. Nous comparons ces deux points de vue pour les revêtements non ramifiés en dehors de $\left\{0,1,\infty \right\}$

Using both class field and Kummer theories, we propose calculations of orders of two Selmer groups, and compare them: the quotient of the orders only depends on local criteria.

The computation of the greatest common divisor (GCD) has many applications in several disciplines including computer graphics, image deblurring problem or computing multiple roots of inexact polynomials. In this paper, Sylvester and Bézout matrices are considered for this purpose. The computation is divided into three stages. A rank revealing method is shortly mentioned in the first one and then the algorithms for calculation of an approximation of GCD are formulated. In the final stage the coefficients...

We prove that the global geometric theta-lifting functor for the dual pair $(H,G)$ is compatible with the Whittaker functors, where $(H,G)$ is one of the pairs $({\mathrm{S}𝕆}_{2n},{𝕊p}_{2n})$, $({𝕊p}_{2n},{\mathrm{S}𝕆}_{2n+2})$ or $({𝔾\mathrm{L}}_n,{𝔾\mathrm{L}}_{n+1})$. That is, the composition of the theta-lifting functor from $H$ to $G$ with the Whittaker functor for $G$ is isomorphic to the Whittaker functor for $H$.