Authors:Samuel Baumard; Leila Schneps Pages: 43 - 62 Abstract: Abstract Richard Hain and Makoto Matsumoto constructed a category of universal mixed elliptic motives, and described the fundamental Lie algebra of this category: it is a semi-direct product of the fundamental Lie algebra \({{\mathrm{Lie}}}\pi _1(\mathsf {MTM})\) of the category of mixed Tate motives over \(\mathbb {Z}\) with a filtered and graded Lie algebra \(\mathfrak {u}\) . This Lie algebra, and in particular \(\mathfrak {u}\) , admits a representation as derivations of the free Lie algebra on two generators. In this paper we study the image \(\mathscr {E}\) of this representation of \(\mathfrak {u}\) , starting from some results by Aaron Pollack, who determined all the relations in a certain filtered quotient of \(\mathscr {E}\) , and gave several examples of relations in low weights in \(\mathscr {E}\) that are connected to period polynomials of cusp forms on \({{\mathrm{SL}}}_2(\mathbb {Z})\) . Pollack’s examples lead to a conjecture on the existence of such relations in all depths and all weights, that we state in this article and prove in depth 3 in all weights. The proof follows quite naturally from Ecalle’s theory of moulds, to which we give a brief introduction. We prove two useful general theorems on moulds in the appendices. PubDate: 2017-04-01 DOI: 10.1007/s40316-015-0040-8 Issue No:Vol. 41, No. 1 (2017)

Authors:Michael Brandenbursky; Jarek Kędra Pages: 63 - 65 Abstract: Abstract We prove that the autonomous norm on the group of compactly supported Hamiltonian diffeomorphisms of the standard \({\mathbf R}^{2n}\) is bounded. PubDate: 2017-04-01 DOI: 10.1007/s40316-016-0065-7 Issue No:Vol. 41, No. 1 (2017)

Authors:Maxim Braverman; Boris Vertman Pages: 67 - 96 Abstract: Abstract We prove that refined analytic torsion on a manifold with boundary is a weakly holomorphic section of the determinant line bundle over the representation variety. As a fundamental application we establish a gluing formula for refined analytic torsion on connected components of the complex representation space which contain a unitary point. Finally we provide a new proof of Brüning-Ma gluing formula for the Ray–Singer torsion associated to a non-Hermitian connection. Our proof is quite different from the one given by Brüning and Ma and uses a temporal gauge transformation. PubDate: 2017-04-01 DOI: 10.1007/s40316-016-0062-x Issue No:Vol. 41, No. 1 (2017)

Authors:Cornelius Greither Pages: 97 - 104 Abstract: Abstract To every abelian Galois extension K / k of number fields with group G, one can associate a so-called Brumer element \(\theta _{K/k,S}\) of the rational group ring \(\mathbb Q[G]\) (depending on another technical parameter S). In a certain sense this element can be thought of as an equivariant version of the class number \(h_K\) . There is a slight problem since this element is only “almost” integral (that is, it may have non-integral coefficients). The potential denominators always divide \(w_K\) , the number of roots of unity in K. Hayes (Contemp Math 358:193–205, 2004) raised the question whether the Brumer element will be p-integral under certain suitable hypotheses, one of which implies that p divides \(h_K\) ; of course only situations with \(p w_K\) are of interest. This paper answers this question in the negative. We start with an “almost counterexample” over \(\mathbb Q\) (for \(k=\mathbb {Q}\) there are no true counterexamples) and manufacture true counterexamples in which k is a suitable real quadratic field. Using deep recent results on the distribution of class numbers (Bhargava et al.) one can show that the method in fact yields infinitely many counterexamples. PubDate: 2017-04-01 DOI: 10.1007/s40316-015-0039-1 Issue No:Vol. 41, No. 1 (2017)

Authors:Suhail Gulzar; N. A Rather; K. A. Thakur Pages: 105 - 110 Abstract: Abstract In this paper, we present certain results on the bounds for the moduli of the zeros of a polynomial with complex coefficients which among other things contain some generalizations and refinements of classical results due to Cauchy, Tôya, Carmichael and Mason, Williams and others. PubDate: 2017-04-01 DOI: 10.1007/s40316-016-0064-8 Issue No:Vol. 41, No. 1 (2017)

Authors:Bernard Helffer Pages: 111 - 118 Abstract: Abstract In a recent paper with Thomas Hoffmann-Ostenhof, we proved that the number of critical points \(\ell _k\) in the boundary set of a minimal k-partition tends to \(+\infty \) as \(k\rightarrow +\infty \) . In this note, we show that \(\ell _k\) increases linearly with k as suggested by a hexagonal conjecture about the asymptotic behavior of the energy of these minimal partitions. As in the original proof by Pleijel of his celebrated theorem, this involves Faber-Krahn’s inequality and Weyl’s formula, but this time, due to the magnetic characterization of the minimal partitions, we have to establish a Weyl’s formula for Aharonov-Bohm operator controlled with respect to a k-dependent number of poles. In a recent paper with Thomas Hoffmann-Ostenhof, we proved that the number of critical points \(\ell _k\) in the boundary set of a k-minimal partition tends to \(+\infty \) as \(k\rightarrow +\infty \) . In this note, we show that \(\ell _k\) increases linearly with k as suggested by a hexagonal conjecture about the asymptotic behavior of the energy of these minimal partitions. As the original proof by Pleijel, this involves Faber-Krahn’s inequality and Weyl’s formula, but this time, due to the magnetic characterization of the minimal partitions, we have to establish a Weyl’s formula for Aharonov-Bohm operator controlled with respect to a k-dependent number of poles. PubDate: 2017-04-01 DOI: 10.1007/s40316-016-0058-6 Issue No:Vol. 41, No. 1 (2017)

Authors:Antonio Lei; Gautier Ponsinet Pages: 155 - 167 Abstract: Abstract We study the functional equation for the multi-signed Selmer groups for non-ordinary motives whose Hodge-Tate weights are 0 and 1, defined by Büyükboduk and the first named author. This generalizes simultaneously Greenberg’s result for ordinary motives in and Kim’s result for supersingular elliptic curves. PubDate: 2017-04-01 DOI: 10.1007/s40316-016-0063-9 Issue No:Vol. 41, No. 1 (2017)

Authors:Ahmed J. Zerouali Pages: 169 - 197 Abstract: Abstract We prove a Hitchin–Thorpe inequality for noncompact 4-manifolds with foliated geometry at infinity by extending on previous work by Dai and Wei. After introducing the objects at hand, we recall some preliminary results regarding the G-signature formula and the rho invariant, which are used to obtain expressions for the signature and Euler characteristic in our geometric context. We then derive our main result, and present examples. PubDate: 2017-04-01 DOI: 10.1007/s40316-016-0066-6 Issue No:Vol. 41, No. 1 (2017)

Authors:Marie José Bertin; Wadim Zudilin Pages: 199 - 211 Abstract: Abstract We prove Boyd’s “unexpected coincidence” of the Mahler measures for two families of two-variate polynomials defining curves of genus 2. We further equate the same measures to the Mahler measures of polynomials \(y^3-y+x^3-x+kxy\) whose zero loci define elliptic curves for \(k\ne 0,\pm 3\) . PubDate: 2017-04-01 DOI: 10.1007/s40316-016-0068-4 Issue No:Vol. 41, No. 1 (2017)

Authors:Aida Kh. Asgarova Abstract: Abstract Assume X is a compact Hausdorff space and C(X) is the space of real-valued continuous functions on X. A version of the Stone–Weierstrass theorem states that a closed subalgebra \(A\subset C(X)\) , which contains a nonzero constant function, coincides with the whole space C(X) if and only if A separates points of X. In this paper, we generalize this theorem to the case in which two subalgebras of C(X) are involved. PubDate: 2017-04-06 DOI: 10.1007/s40316-017-0081-2

Authors:Jean-Marie De Koninck; Imre Kátai Abstract: Abstract We show that some sequences of real numbers involving sharp normal numbers or non-Liouville numbers are uniformly distributed modulo 1. In particular, we prove that if \(\tau (n)\) stands for the number of divisors of n and \(\alpha \) is a binary sharp normal number, then the sequence \((\alpha \tau (n))_{n\ge 1}\) is uniformly distributed modulo 1 and that if g(x) is a polynomial of positive degree with real coefficients and whose leading coefficient is a non-Liouville number, then the sequence \((g(\tau (\tau (n))))_{n \ge 1}\) is also uniformly distributed modulo 1. PubDate: 2017-04-04 DOI: 10.1007/s40316-017-0080-3

Authors:Jeehoon Park Abstract: Abstract G. Stevens (http://math.bu.edu/people/ghs/research.html) constructed a modular symbol taking values in circular K-groups, which is intimately related to Eisenstein series. We make precise a relationship between his Milnor K-theoretic modular symbol \(\Phi _{MK}\) and the period integrals of Eisenstein series. The main goal here is to extract from \(\Phi _{MK}\) a group 1-cocyle on \({{\mathrm{SL}}}_2(\mathbb {Q})\) with values in differential form valued distributions and use this to construct a p-adic locally analytic distribution which gives a p-adic partial zeta function of a real quadratic field. PubDate: 2017-02-22 DOI: 10.1007/s40316-017-0079-9

Authors:Philippe Charron; Bernard Helffer; Thomas Hoffmann-Ostenhof Abstract: Abstract In 1956, Pleijel gave his celebrated theorem showing that the inequality in Courant’s theorem on the number of nodal domains is strict for large eigenvalues of the Laplacian. This was a consequence of a stronger result giving an asymptotic upper bound for the number of nodal domains of the eigenfunction as the eigenvalue tends to \(+\infty \) . A similar question occurs naturally for the case of the Schrödinger operator. The first significant result has been obtained recently by the first author for the case of the harmonic oscilllator. The purpose of this paper is to consider more general potentials which are radial. We will analyze either the case when the potential tends to \(+\infty \) or the case when the potential tends to zero, the considered eigenfunctions being associated with the eigenvalues below the essential spectrum. PubDate: 2017-02-01 DOI: 10.1007/s40316-017-0078-x

Authors:Bruno Poizat Abstract: Abstract We define in the infinitely generated free models of an arbitrary equational class an independence relation, which is necessarily the model-theoretic independence over the empty set when these structures happen to be \(\upomega \) -homogeneous stable groups. We establish the basic properties of this independence relation, give some examples, and ask some questions concerning its model-theoretic behaviour (many of them dealing with the treatment of the free models in Positive Logic). PubDate: 2016-12-19 DOI: 10.1007/s40316-016-0075-5

Authors:Stéphane Dellacherie; Olivier Lafitte Abstract: Abstract We study a monodimensional stationary system coupling a simplified thermohydraulic model to a simplified neutronic model based on the diffusion approximation with one energy group. We observe that this non-linear coupled model can be studied under two points of view and we show that solving this model is equivalent to the resolution of a non-linear scalar autonomous ordinary differential equation of order 1. As a consequence, it is possible to obtain an explicit solution without using an iterative coupling algorithm solving successively the thermohydraulics and the neutronics. Moreover, we obtain an analytic solution in a simple case. The explicit results obtained with our analytical solutions confirm the numerical results obtained with the iterative classical thermohydraulics–neutronics algorithm. PubDate: 2016-11-22 DOI: 10.1007/s40316-016-0073-7

Authors:Kevin Buzzard; Alan Lauder Abstract: Abstract We report on a computation of holomorphic cuspidal modular forms of weight one and small level (currently level at most 1500) and classification of them according to the projective image of their attached Artin representations. The data we have gathered, such as Fourier expansions and projective images of Hecke newforms and dimensions of space of forms, is available in both Magma and Sage readable formats on a webpage created in support of this project. PubDate: 2016-11-10 DOI: 10.1007/s40316-016-0072-8

Authors:Jean-François Jaulent Abstract: Abstract We use \(\ell \) -adic class field theory to take a new view on cyclotomic norms and Leopoldt or Gross-Kuz’min conjectures. By the way we recall and complete some classical results. We illustrate the logarithmic approach by various numerical examples and counter-examples obtained with PARI. PubDate: 2016-10-28 DOI: 10.1007/s40316-016-0069-3

Authors:Robert Laterveer Abstract: Abstract Let X be a smooth cubic hypersurface, and let F be the Fano variety of lines on X. We establish a relation between the Chow motives of X and F. This relation implies in particular that if X has finite-dimensional motive (in the sense of Kimura), then F also has finite-dimensional motive. This proves finite-dimensionality for motives of Fano varieties of cubics of dimension 3 and 5, and of certain cubics in other dimensions. PubDate: 2016-10-22 DOI: 10.1007/s40316-016-0070-x

Authors:Dylan Attwell-Duval Abstract: Abstract We study the boundary of orthogonal Shimura varieties associated to a positive multiple of a maximal lattice splitting two hyperbolic planes. We provide closed formulas for the number of 0 and 1-dimensional cusps of these spaces and study their configuration within the boundary. This generalizes our earlier results about maximal lattices. PubDate: 2016-08-02 DOI: 10.1007/s40316-016-0067-5