Let p be a prime number ≥ 11 and c be a square-free integer ≥ 3. In this paper, we study the diophantine equation $x^p-y^p=cz²$ in the case where p belongs to 11,13,17. More precisely, we prove that for those primes, there is no integer solution (x,y,z) to this equation satisfying gcd(x,y,z) = 1 and xyz ≠ 0 if the integer c has the following property: if ℓ is a prime number dividing c then ℓ ≢ 1 mod p. To obtain this result, we consider the hyperelliptic curves $C_p:y²={\Phi }_p\left(x\right)$ and $D_p:py²={\Phi }_p\left(x\right)$, where ${\Phi }_p$ is the pth cyclotomic...

We denote by the unit circle and by the unit disc of ℂ. Let s be a non-negative real and ω a weight such that $\omega \left(n\right)={(1+n)}^s$ (n ≥ 0) and the sequence ${(\omega (-n)/{(1+n)}^s)}_{n\ge 0}$ is non-decreasing. We define the Banach algebra $A_{\omega }\left(\right)={f\in \left(\right):\left|\right|f\left|\right|}_{\omega }={\sum }_{n=-\infty }^{+\infty }\left|f̂\left(n\right)\right|\omega \left(n\right)<+\infty$. If I is a closed ideal of $A_{\omega }\left(\right)$, we set $h⁰\left(I\right)=z\in :f\left(z\right)=0\left(f\in I\right)$. We describe all closed ideals I of $A_{\omega }\left(\right)$ such that h⁰(I) is at most countable. A similar result is obtained for closed ideals of the algebra $A{⁺}_s\left(\right)=f\in A_{\omega }\left(\right):f̂\left(n\right)=0(n<0)$ without inner factor. Then we use this description to establish a link between operators with countable spectrum and interpolating...

Let Ω(n) and ω(n) denote the number of distinct prime factors of the positive integer n, counted respectively with and without multiplicity. Let $d_k\left(n\right)$ denote the Piltz function (which counts the number of ways of writing n as a product of k factors). We obtain a precise estimate of the sum ${\sum }_{n\le x,\Omega \left(n\right)-\omega \left(n\right)=q}f\left(n\right)$ for a class of multiplicative functions f, including in particular $f\left(n\right)=d_k\left(n\right)$, unconditionally if 1 ≤ k ≤ 3, and under some reasonable assumptions if k ≥ 4. The result also applies to f(n) = φ(n)/n (where φ is...

We prove existence (uniqueness is easy) of a weak solution to a boundary value problem for an equation like ${(v-1)}_t^{+}=v_{xx}+F{\left(v\right)}_x$ where the function $F:ℝ\to ℝ$ is only supposed to be locally lipschitz continuous. In order to replace the lack of compactness in on , we use nonlinear semigroup theory.

Let k be a commutative field. For any a,b∈ k, we denote by $J_{a,b}\left(k\right)$ the deformation of the 2-dimensional Weyl algebra over k associated with the Jordanian Hecke symmetry with parameters a and b. We prove that: (i) any $J_{a,b}\left(k\right)$ can be embedded in the usual Weyl algebra A₂(k), and (ii) $J_{a,b}\left(k\right)$ is isomorphic to A₂(k) if and only if a = b.

By getting uniformly asymptotic estimates for the Poisson kernel on Heisenberg groups ${ℍ}_{2n+1}$, we prove that there exists a constant A > 0, independent of n ∈ ℕ*, such that for all $f\in L¹\left({ℍ}_{2n+1}\right)$, we have ${\left|\right|Mf\left|\right|}_{L^{1,\infty }}\le An\left|\right|f\left|\right|₁$, where M denotes the centered Hardy-Littlewood maximal function defined by the Carnot-Carathéodory distance or by the Korányi norm.

Let p be a prime, and let ℱ be the category of functors from the finite ${}_p$-vector spaces to all ${}_p$-vector spaces. The object Id of ℱ is the inclusion functor. Let F and G be two objects in ℱ. If F and G satisfy suitable conditions, the main result of this paper allows one to compute $Ext{*}_{ℱ}(Id,G\circ F)$ from the knowledge of $Ext{*}_{ℱ}(Id,F)$ and $Ext{*}_{ℱ}(Id,G)$.

We prove in this paper that the types of system $ℱ$ inhabited uniquely by λ-terms (the -types) have a positive quantifier. We give also consequences of this result and some examples.

On a metric measure space (X,ϱ,μ), consider the weight functions $w_{\alpha }\left(x\right)=\varrho {(x,z₀)}^{-\alpha ₀}$ if ϱ(x,z₀) < 1, $w_{\alpha }\left(x\right)=\varrho {(x,z₀)}^{-\alpha ₁}$ if ϱ(x,z₀) ≥ 1, $w_{\beta }\left(x\right)=\varrho {(x,z₀)}^{-\beta ₀}$ if ϱ(x,z₀) < 1, $w_{\beta }\left(x\right)=\varrho {(x,z₀)}^{-\beta ₁}$ if ϱ(x,z₀) ≥ 1, where z₀ is a given point of X, and let ${\kappa }_a:X\times X\to ℝ₊$ be an operator kernel satisfying ${\kappa }_a(x,y)\le c\varrho {(x,y)}^{a-d}$ for all x,y ∈ X such that ϱ(x,y) < 1, ${\kappa }_a(x,y)\le c\varrho {(x,y)}^{a-D}$ for all x,y ∈ X such that ϱ(x,y)≥ 1, where 0 < a < min(d,D), and d and D are respectively the local and global volume growth rate of the space X. We determine conditions on a, α₀, α₁, β₀, β₁ ∈ ℝ for the Hardy-Littlewood-Sobolev...

Let Ω be a domain of finite type in ℂ² and let f be a function holomorphic in Ω and belonging to ${}^{k,\alpha }\left(\Omega ̅\right)$. We prove the existence of boundary values for some suitable derivatives of f of order greater than k. The gain of derivatives holds in the complex-tangential direction and it is precisely related to the geometry of ∂Ω. Then we prove a property of non-isotropic Hölder regularity for these boundary values. This generalizes some results given by J. Bruna and J. M. Ortega for the unit ball. ...

Generalizing the classical BMO spaces defined on the unit circle with vector or scalar values, we define the spaces $BM{O}_{{\psi }_q}\left(\right)$ and $BM{O}_{{\psi }_q}(,B)$, where ${\psi }_q\left(x\right)=e^{x^q}-1$ for x ≥ 0 and q ∈ [1,∞[, and where B is a Banach space. Note that $BM{O}_{{\psi }_1}\left(\right)=BMO\left(\right)$ and $BM{O}_{{\psi }_1}(,B)=BMO(,B)$ by the John-Nirenberg theorem. Firstly, we study a generalization of the classical Paley inequality and improve the Blasco-Pełczyński theorem in the vector case. Secondly, we compute the idempotent multipliers of $BM{O}_{{\psi }_q}\left(\right)$. Pisier conjectured that the supports of idempotent multipliers of...

Let G be a compact metric infinite abelian group and let X be a Banach space. We study the following question: if the dual X* of X does not have the Radon-Nikodym property, is $L^p(G,X*)$ complemented in $L^q(G,X)*$, 1 < p ≤ ∞, 1/p + 1/q = 1, or, if p = 1, in the subspace of C(G,X)* consisting of the measures that are absolutely continuous with respect to the Haar measure? We show that the answer is negative if X is separable and does not contain ℓ¹, and if 1 ≤ p < ∞. If p = 1, this answers a question...

We give a description of Kähler manifolds $M$ equipped with an integrable subbundle $ℱ$ of $TM$ of rank $n-1$ ($n=\dim M$) under the assumption that the line bundle $\mathrm{D}é\mathrm{t}ℱ$ is numerically trivial. This is a sort of foliated version of Bogomolov’s theorem concerning Kähler manifolds with trivial canonical class.

We consider supersymmetric matrix Hamiltonians. The existence of a zero-energy bound state, in particular for the $d=9$ model, is of interest in M-theory. While we do not quite prove its existence, we show that the decay at infinity such a state would have is compatible with normalizability (and hence existence) in $d=9$. Moreover, it would be unique. Other values of $d$, where the situation is somewhat different, shall also be addressed. The analysis is based on a Born-Oppenheimer approximation....

In this paper, we are giving parameters for discrete series of classical $p$-adic groups. We first define: the analogous of the Langlands morphism of $W_F$ in the $L$-group, part of the analogous of the character of the centralizer of that morphism and, to supply the missing part of the full definition of that character, the cuspidal support of the representation. Then, we state an hypothesis on the reducibility points for induced of cuspidal representations. And we prove that, under this hypothesis,...

We consider subrings A of the ring of formal power series. They are defined by growth conditions on coefficients such as, for instance, Gevrey conditions. We prove preparation theorems of Malgrange type in these rings. As a consequence we study maps F from ${ℂ}^s$ to ${ℂ}^p$ without constant term such that the rank of the Jacobian matrix of F is equal to 1. Let be a formal power series. If F is a holomorphic map, the following result is well known: ∘ F is analytic implies there exists a convergent...

On prouve que le problème de Cauchy local pour l’équation d’onde sur-critique dans ${ℝ}^d$, $\square u+u^p=0$, $p$ impair, avec $d\ge 3$ et $p\&gt;(d+2)/(d-2)$, est mal posé dans $H^{\sigma }$ pour tout $\sigma \in ]1,{\sigma }_{\mathrm{crit}}[$, où ${\sigma }_{\mathrm{crit}}=d/2-2/(p-1)$ est l’exposant critique.

Taking an odd increasing Lipschitz-continuous function with polynomial growth β, an odd Lipschitz-continuous and bounded function ϕ satisfying sgn(x)ϕ(x) ≥ 0 and a parameter a ∈ [1/2,1], we consider the (nonlinear) stochastic differential system ⎧$X_t=X₀+B_t+a{\int }_0^t\varphi *v_s\left(X_s\right)ds-(1-a){\int }_0^t\beta *u_s\left(X_s\right)ds$, (E)⎨ ⎩$Y_t=Y₀+B{̃}_t+(1-a){\int }_0^t\varphi *u_s\left(Y_s\right)ds-a{\int }_0^t\beta *v_s\left(Y_s\right)ds$, $\mathbb{P}\left(X_t\in dx\right)=u_t\left(dx\right)$ and $\mathbb{P}\left(Y_t\in dx\right)=v_t\left(dx\right)$, where $\beta *u_t\left(x\right)={\int }_{ℝ}\beta (x-y)u_t\left(dy\right)$, ${\left(B_t\right)}_{t\ge 0}$ and ${\left(B{̃}_t\right)}_{t\ge 0}$ are independent Brownian motions. We show that (E) admits a stationary probability measure, and, under some additional conditions, that $(X_t,Y_t)$ converges in distribution to this invariant measure. Moreover we...

Let K be a finite extension of ℚ₂ complete with a discrete valuation v, K̅ an algebraic closure of K, and $K_{nr}$ its maximal unramified subextension. Let E be an elliptic curve defined over K with additive reduction over K and having an integral modular invariant j. There exists a smallest extension L of $K_{nr}$ over which E has good reduction. For some congruences modulo 12 of the valuation v(j) of j, we give the degree of the extension $L/K_{nr}$. When K is a quadratic ramified extension of ℚ₂, we determine...

Dans ce travail, on s’intéresse à l’existence globale de solutions classiques et au sens de Shatah-Struwe de l’équation des ondes critique à coefficients variables en dimension $d$ d’espace $${\square }_{A}u+{\left|u\right|}^{4/(d-2)}u={\partial }_t^{2}u-\mathrm{div}(A\left(x\right)·{\nabla }_{x}u)+{\left|u\right|}^{4/(d-2)}u=0,{ℝ}_t\times {ℝ}_x^d,$$ où $A$ est une fonction régulière à valeurs dans les matrices $d\times d$ définies positives, valant l’identité en dehors d’un compact fixe.