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Volume 50 Number 2 (Jun 2007)
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161   Arapura, Donu; Kang, Su-Jeong
Functoriality of the Coniveau Filtration
It is shown that the coniveau filtration on the cohomology of smooth projective varieties is preserved up to shift by pushforwards, pullbacks and products.
172   Aron, Richard; Gorkin, Pamela
An Infinite Dimensional Vector Space of Universal Functions for $H^\infty$ of the Ball
We show that there exists a closed infinite dimensional subspace of Hinfty(Bn) such that every function of norm one is universal for some sequence of automorphisms of Bn.
182   Chapoton, Frédéric
On the Coxeter Transformations for Tamari Posets
A relation between the anticyclic structure of the dendriform operad and the Coxeter transformations in the Grothendieck groups of the derived categories of modules over the Tamari posets is obtained.
191   Drungilas, Paulius; Dubickas, Art\={u}ras
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
196   Fernández, Julio; González, Josep; Lario, Joan-C.
Plane Quartic Twists of $X(5,3)$
Given an odd surjective Galois representation varrho : G(mathbb Q) \to PGL2((mathbb F)3) and a positive integer N, there exists a twisted modular curve X(N,3)varrho defined over mathbb Q whose rational points classify the quadratic mathbb Q-curves of degree N realizing varrho. This paper gives a method to provide an explicit plane quartic model for this curve in the genus-three case N = 5.
206   Golasi\'nski, Marek; Gon\c{c}alves, Daciberg Lima
Spherical Space Forms: Homotopy Types and Self-Equivalences for the Group $({\mathbb Z}/a\rtimes{\mathbb Z}/b) \times SL_2\,(\mathbb{F}_p)$
Let G = ({mathbb Z} / a \rtimes {mathbb Z} / b) \times SL2 (mathbb{F}p), and let X(n) be an n-dimensional CW-complex of the homotopy type of an n-sphere. We study the automorphism group Aut (G) in order to compute the number of distinct homotopy types of spherical space forms with respect to free and cellular G-actions on all CW-complexes X(2dn - 1), where 2d is the period of G. The groups {mathcal E}(X(2dn - 1) / mu) of self homotopy equivalences of space forms X(2dn - 1) / mu associated with free and cellular G-actions mu on X(2dn - 1) are determined as well.
Keywords:automorphism group, $CW$-complex, free and cellular $G$-action, group of self homotopy equivalences, Lyndon--Hochschild--Serre spectral sequence, special (linear) group, spherical space form
215   Kloosterman, Remke
Elliptic $K3$ Surfaces with Geometric Mordell--Weil Rank $15$
We prove that the elliptic surface y2 = x3 + 2(t8 + 14t4 + 1) x + 4t2 (t8 + 6t4 + 1) has geometric Mordell–Weil rank 15. This completes a list of Kuwata, who gave explicit examples of elliptic K3-surfaces with geometric Mordell–Weil ranks 0, 1, dots, 14, 16, 17, 18.
227   Kucerovsky, D.; Ng, P. W.
AF-Skeletons and Real Rank Zero Algebras with the Corona Factorization Property
Let A be a stable, separable, real rank zero C*-algebra, and suppose that A has an AF-skeleton with only finitely many extreme traces. Then the corona algebra {mathcal M}(A)/A is purely infinite in the sense of Kirchberg and Rordam, which implies that A has the corona factorization property.
234   Kuo, Wentang
A Remark on a Modular Analogue of the Sato--Tate Conjecture
The original Sato–Tate Conjecture concerns the angle distribution of the eigenvalues arising from non-CM elliptic curves. In this paper, we formulate a modular analogue of the Sato–Tate Conjecture and prove that the angles arising from non-CM holomorphic Hecke eigenforms with non-trivial central characters are not distributed with respect to the Sate–Tate measure for non-CM elliptic curves. Furthermore, under a reasonable conjecture, we prove that the expected distribution is uniform.
Keywords:$L$-functions, Elliptic curves, Sato--Tate
243   Langlands, Robert P.
Un nouveau point de repère dans la théorie des formes automorphes
Dans le papier Beyond Endoscopy une idée pour entamer la fonctorialité en utilisant la formule des traces a été introduite. Maints problèmes, l'existence d'une limite convenable de la formule des traces, est eqquissée dans cette note informelle mais seulement pour GL(2) et les corps des fonctions rationelles sur un corps fini et en ne pas resolvant bon nombre de questions.
268   Manuilov, V.; Thomsen, K.
On the Lack of Inverses to $C^*$-Extensions Related to Property T Groups
Using ideas of S. Wassermann on non-exact C*-algebras and property T groups, we show that one of his examples of non-invertible C*-extensions is not semi-invertible. To prove this, we show that a certain element vanishes in the asymptotic tensor product. We also show that a modification of the example gives a C*-extension which is not even invertible up to homotopy.
Keywords:$C^*$-algebra extension, property T group, asymptotic tensor $C^*$-norm, homotopy
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 e2 pi ir (r rational), there is a theta function Fr(q) with F(q) - Fr (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
291   Sarkar, Rudra P.; Sengupta, Jyoti
Beurling's Theorem and Characterization of Heat Kernel for Riemannian Symmetric Spaces of Noncompact Type
We prove Beurling's theorem for rank 1 Riemannian symmetric spaces and relate its consequences with the characterization of the heat kernel of the symmetric space.
Keywords:Beurling's Theorem, Riemannian symmetric spaces, uncertainty principle
313   Tzermias, Pavlos
On Cauchy--Liouville--Mirimanoff 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 Cauchy–Liouville–Mirimanoff 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 Pólya and Szegö. These conditions are conjecturally also necessary for irreducibility.

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