Let $G=\left( \mathbb{Z}/a\rtimes \mathbb{Z}/b \right)\times \text{S}{{\text{L}}_{2}}\left( {{\mathbb{F}}_{p}} \right)$, and let $X\left( n \right)$ be an $n$-dimensional $CW$-complex of the homotopy type of an $n$-sphere. We study the automorphism group $\text{Aut}\left( G \right)$ 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 $X\left( 2dn-1 \right)$, where $2d$ is the period of $G$. The groups $\varepsilon \left( X\left( 2dn-1 \right)/\mu \right)$ of self homotopy equivalences of space forms $X\left( 2dn-1 \right)/\mu$ associated with free and cellular $G$-actions $\mu$ on $X\left( 2dn-1 \right)$ are determined as well.

The paper offers a study of the inverse Laplace transforms of the functions ${{I}_{n}}\left( rs \right)\,{{\{sI_{n}^{\prime }\,\left( s \right)\}}^{-1}}$ where ${{I}_{n}}$ is the modified Bessel function of the first kind and $r$ is a parameter. The present study is a continuation of the author's previous work on the singular behavior of the special case of the functions in question, $r=1$. The general case of $r\,\in \,\left[ 0,\,1 \right]$ is addressed, and it is shown that the inverse Laplace transforms for such $r$ exhibit significantly more complex behavior than their predecessors, even though they still only have two different types of points of discontinuity: singularities and finite discontinuities. The functions studied originate from non-stationary fluid-structure interaction, and as such are of interest to researchers working in the area.

We study two sufficient conditions that imply global injectivity for a ${{C}^{1}}$ map $X:{{\mathbb{R}}^{2}}\to {{\mathbb{R}}^{2}}$ such that its Jacobian at any point of ${{\mathbb{R}}^{2}}$ is not zero. One is based on the notion of half-Reeb component and the other on the Palais–Smale condition. We improve the first condition using the notion of inseparable leaves. We provide a new proof of the sufficiency of the second condition. We prove that both conditions are not equivalent, more precisely we show that the Palais–Smale condition implies the nonexistence of inseparable leaves, but the converse is not true. Finally, we show that the Palais–Smale condition it is not a necessary condition for the global injectivity of the map $X$.

In this paper, we investigate the higher simplicial cohomology groups of the convolution algebra ${{\ell }^{1}}\left( S \right)$ for various semigroups $S$. The classes of semigroups considered are semilattices, Clifford semigroups, regular Rees semigroups and the additive semigroups of integers greater than $a$ for some integer $a$. Our results are of two types: in some cases, we show that some cohomology groups are 0, while in some other cases, we show that some cohomology groups are Banach spaces.

We prove that the elliptic surface ${{y}^{2}}={{x}^{3}}+2\left( {{t}^{8}}+14{{t}^{4}}+1 \right)x+4{{t}^{2}}\left( {{t}^{8}}+6{{t}^{4}}+1 \right)$ 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, … , 14, 16, 17, 18.

We extend the notion of linking number of an ordinary link of two components to that of a singular link with transverse intersections, in which case the linking number is a half-integer. We then apply it to simplify the construction of the Seifert matrix, and therefore the Alexander polynomial, in a natural way.

In this paper we show that any Frobenius split, smooth, projective threefold over a perfect field of characteristic $p\,>\,0$ is Hodge–Witt. This is proved by generalizing to the case of threefolds a well-known criterion due to $\text{N}$. Nygaard for surfaces to be Hodge-Witt. We also show that the second crystalline cohomology of any smooth, projective Frobenius split variety does not have any exotic torsion. In the last two sections we include some applications.

Fix an integer $m>1$, and set ${{\zeta }_{m}}=\exp \left( 2\pi i/m \right)$. Let $\bar{x}$ denote the multiplicative inverse of $x$ modulo $m$. The Kloosterman sums $R\left( d \right)=\sum\limits_{x}{\zeta _{m}^{x+d\bar{x}}},1\le d\le m,\left( d,m \right)=1$, satisfy the polynomial

$${{f}_{m}}\left( x \right)=\underset{d}{\mathop{\prod }}\,\left( x-R\left( d \right) \right)={{x}^{\phi \left( m \right)}}+{{c}_{1}}{{x}^{\phi \left( m \right)-1}}+\cdot \cdot \cdot +{{c}_{\phi \left( m \right)}},$$

where the sum and product are taken over a complete system of reduced residues modulo $m$. Here we give a natural factorization of ${{f}_{m}}\left( x \right)$, namely,

$${{f}_{m}}\left( x \right)=\underset{\sigma }{\mathop{\prod }}\,f_{m}^{\left( \sigma \right)}\left( x \right),$$

where $\sigma$ runs through the square classes of the group $Z_{m}^{*}$ of reduced residues modulo $m$. Questions concerning the explicit determination of the factors $f_{m}^{\left( \sigma \right)}\left( x \right)$ (or at least their beginning coefficients), their reducibility over the rational field $\text{Q}$ and duplication among the factors are studied. The treatment is similar to what has been done for period polynomials for finite fields.

For $p\,>\,0$ and for a given set $E$ of type ${{G}_{\delta }}$ in the boundary of the unit disc $\partial \mathbb{D}$ we construct a holomorphic function $f\,\in \,\mathbb{O}\left( \mathbb{D} \right)$ such that

$${{\int_{\mathbb{D}\backslash \left[ 0,\,1 \right]E}{\left| f \right|}}^{p}}\,d{{\mathfrak{L}}^{2}}\,<\,\infty \,\text{and}\,E\,=\,{{E}^{p}}\left( f \right)\,=\,\{\,z\,\in \,\partial \mathbb{D}\,:\,\int _{0}^{1}\,{{\left| f\left( tz \right) \right|}^{p}}\,dt\,=\,\infty \}.$$

In particular if a set $E$ has a measure equal to zero, then a function $f$ is constructed as integrable with power $p$ on the unit disc $\mathbb{D}$.

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 $\mathcal{M}\left( A \right)/A$ is purely infinite in the sense of Kirchberg and Rørdam, which implies that $A$ has the corona factorization property.

Beginning with a seminal paper of Rényi, 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 Daróczy and Kátai for expansions in complex bases. We introduce an adaptation of the so-called greedy algorithm to the complex case, and we generalize one of their main theorems.

Given a finite group $G$, we examine the classification of all frame representations of $G$ and the classification of all $G$-frames, i.e., frames induced by group representations of $G$. We show that the exact number of equivalence classes of $G$-frames and the exact number of frame representations can be explicitly calculated. We also discuss how to calculate the largest number $L$ such that there exists an $L$-tuple of strongly disjoint $G$-frames.

We show that, for most of the elliptic curves $\text{E}$ over a prime finite field ${{\mathbb{F}}_{p}}$ of $p$ elements, the discriminant $D\left( E \right)$ of the quadratic number field containing the endomorphism ring of $\text{E}$ over ${{\mathbb{F}}_{p}}$ is sufficiently large. We also obtain an asymptotic formula for the number of distinct quadratic number fields generated by the endomorphism rings of all elliptic curves over ${{\mathbb{F}}_{p}}$.

We study a real hypersurface $M$ in a complex space form ${{M}_{n}}\left( c \right),c\ne 0$, whose shape operator and structure tensor commute each other on the holomorphic distribution of M.

Let $p$ be a prime and $F$ a field containing a primitive $p$-th root of unity. Then for $n\,\in \,\mathbb{N}$, the cohomological dimension of the maximal pro-$p$-quotient $G$ of the absolute Galois group of $F$ is at most $n$ if and only if the corestriction maps ${{H}^{n}}\left( H,\ {{\mathbb{F}}_{p}} \right)\,\to \,{{H}^{n}}\left( G,\ {{\mathbb{F}}_{p}} \right)$ are surjective for all open subgroups $H$ of index $p$. Using this result, we generalize Schreier's formula for ${{\dim}_{{{\mathbb{F}}_{p}}}}\,{{H}^{1}}\,\left( H,\ {{\mathbb{F}}_{p}} \right)$ to ${{\dim}_{{{\mathbb{F}}_{p}}}}{{H}^{n}}\left( H,\ {{\mathbb{F}}_{p}} \right)$.

The original Sato–Tate Conjecture concerns the angle distribution of the eigenvalues arising from non-CM elliptic curves. In this paper, we formulate amodular analogue of the Sato–Tate Conjecture and prove that the angles arising from non-$\text{CM}$ holomorphic Hecke eigenforms with non-trivial central characters are not distributed with respect to the Sate–Tatemeasure for non-$\text{CM}$ elliptic curves. Furthermore, under a reasonable conjecture, we prove that the expected distribution is uniform.

We will show that any extension of a product of two Cantor minimal $\mathbb{Z}$-systems is affable in the sense of Giordano, Putnam and Skau.

Soit $q$ une puissance d’un nombre premier $p$. Dans cette note on établit la généralisation suivante d’un théorème de Wintenberger : tout sous-groupe abélien fermé du groupe des ${{\mathbb{F}}_{q}}$-automorphismes continus du corps des séries formelles ${{\mathbb{F}}_{q}}((X\text{))}$ muni de sa filtration de ramification est un groupe filtré isomorphe au groupe de Galois d’une extension abélienne d’un corps local à corps résiduel ${{\mathbb{F}}_{q}}$, filtré par les groupes de ramification de l’extension en numérotation inférieure.

We study natural $*$-valuations, $*$-places and graded $*$-rings associated with $*$-ordered rings. We prove that the natural $*$-valuation is always quasi-Ore and is even quasi-commutative (i.e., the corresponding graded $*$-ring is commutative), provided the ring contains an imaginary unit. Furthermore, it is proved that the graded $*$-ring is isomorphic to a twisted semigroup algebra. Our results are applied to answer a question of Cimprič regarding $*$-orderability of quantum groups.

Ceux qui connaissent l’auteur et ses écrits, comme par exemple $\left[ \text{L1} \right]$ et $\left[ \text{L2} \right]$, savent que la notion de fonctorialité et les conjectures rattachées à celle-ci ont été introduites —en suivant ce que Artin avait fait pour un ensemble plus restreint de fonctions— pour aborder le problème de la prolongation analytique générale des fonctions $L$-automorphes. Ils savent en plus que je suis d’avis que seules les méthodes basées sur la formule des traces pourront aller au fond des problèmes. Il n’en reste pas moins que malgré de récents progrès importants sur le lemme fondamental et la formule des traces nous sommes bien loin de notre but.