On Waring's Problem for Cubes and Smooth Weyl Sums

Non-trivial estimates for fractional moments of smooth cubicWeyl sums are developed. Complemented by bounds for such sumsof use on both the major and minor arcs in a Hardy-Littlewooddissection, these estimates are applied to derive an upper boundfor the sth moment of the smooth cubic Weyl sum of the expectedorder of magnitude as soon as s> 7.691. Related argumentsdemonstrate that all large integers n are represented as thesum of eight cubes of natural numbers, all of whose prime divisorsare at most exp (c(log nlog log n)^1/2}, for a suitable positivenumber c. This conclusion improves a previous result of G. Harcosin which nine cubes are required. 1991 Mathematics Subject Classification:11P05, 11L15, 11P55.     

Weak Laws of Large Numbers in Some Non-Commutative Spaces

We prove weak laws of large numbers for freely independent,uniformly bounded and non-identically distributed random variablesbelonging to non-commutative Ciach and, in particular, LorentzL^p-spaces. 2000 Mathematics Subject Classification 60B11, 60F25,46L54, 47N30.     

Factorization in finite-codimensional ideals of group algebras

Let G be a -compact, locally compact group and I be a closed2-sided ideal with finite codimension in L¹(G). It is shownthat there are a closed left ideal L having a right boundedapproximate identity and a closed right ideal R having a leftbounded approximate identity such that I = L + R. The proofuses ideas from the theory of boundaries of random walks ongroups. 2000 Mathematics Subject Classification: primary 43A20;secondary 42A85, 43A07, 46H10, 46H40, 60B11.     

On the Exponential Sum with Square-Free Numbers

A new estimate for the exponential sum with square-free numbersis established. This result is applied to the problem of findingthe number of representations of a large integer as a sum ofthree square-free numbers. 2000 Mathematics Subject Classification11L07, 11N36, 11P99.     

On the Distribution of Power Residues and Primitive Elements in Some Nonlinear Recurring Sequences

It is shown that the method of estimation of exponential sumswith nonlinear recurring sequences, invented by the authorsin a recent series of works, can be applied to estimating sumsof multiplicative characters as well. As a consequence, resultsare obtained about the distribution of power residues and primitiveelements in such sequences. 2000 Mathematics Subject Classification11B37, 11L40 (primary), 11A07, 11A15, 11T24 (secondary).     

Some Characterizations of Commutative Subspace Lattices

Let H be a not necessarily separable Hilbert space, and letBH denote the space of all bounded linear operators on H. Itis proved that a commutative lattice D of self-adjoint projectionsin H that contains 0 and I is spatially complete if and onlyif it is a closed subset of BH in the strong operator topology.Some related results are obtained concerning commutative lattice-orderedcones of self-adjoint operators that contain D. 2000 MathematicsSubject Classification 47D03, 47L35, 47L07, 46L10, 54F05, 54G05,46E05.     

On the Representation of Primes by Cubic Polynomials in Two Variables

In an earlier paper (see Proc. London Math. Soc. (3) 84 (2002)257–288) we showed that an irreducible integral binarycubic form f(x, y) attains infinitely many prime values, providingthat it has no fixed prime divisor. We now extend this resultby showing that f(m, n) still attains infinitely many primevalues if m and n are restricted by arbitrary congruence conditions,providing that there is still no fixed prime divisor. Two immediate consequences for the solvability of diagonal cubicDiophantine equations are given. 2000 Mathematics Subject Classification11N32 (primary), 11N36, 11R44 (secondary).     

The Mathieu Group M11 and the Modular Curve X(11)

In this paper, we prove that the modular curve X(11) over afield of characteristic 3 admits the Mathieu group M₁₁ as anautomorphism group. We also examine some aspects of the geometryof the curve X(11) in characteristic 3. In particular, we showthat every point of the curve is a point of inflection, thecurve has 110 hyperflexes and there are no inflectional trianglesand 11232 inflectional pentagons, of which 144 are self-conjugate.The hyperflexes correspond to the supersingular elliptic curves.We comment on the relationship of Ward's quadrilinear invariantfor M₁₂ to our work and announce for the first time the equationsfor Klein's A-curve of level 11. We also comment on the relationof our work to some unpublished work of Bott and Tate. 1991Mathematics Subject Classification: 11F32, 11G20, 14G10, 14H10,14N10, 20B25, 20C34.     

Primes Represented by Binary Cubic Forms

Let f(x, y) be a binary cubic form with integral rational coefficients,and suppose that the polynomial f(x, y) is irreducible in Q[x,y] and no prime divides all the coefficients of f. We provethat the set f Z⁽²⁾ contains infinitely many primes unless f(a,b) is even for each (a,b) in Z², in which case the set contains infinitely many primes. 2000Mathematical Subject Classification: primary 11N32; secondary11N36, 11R44.     

S-adic L-Functions Attached to the Symmetric Square of a Newform

In order to apply the ideas of Iwasawa theory to the symmetricsquare of a newform, we need to be able to define non-archimedeananalogues of its complex L-series. The interpolated p-adic L-functionis closely connected via a "Main Conjecture" with certain Selmergroups over the cyclotomic Z_p-extension of Q. In the p-ordinarycase these functions are well understood. In this article we extend the interpolation to an arbitraryset S of good primes (not necessarily satisfying ordinarityconditions). The corresponding S-adic functions can be characterisedin terms of certain admissibility criteria. We also allow interpolationat particular primes dividing the level of the newform. One interesting application is to the symmetric square of amodular elliptic curve E defined over Q. Our constructions yieldp-adic L-functions at all primes of stable or semi-stable reduction.If p is ordinary or multiplicative the corresponding analyticfunction is bounded; if p is supersingular our function behaveslike log²(1 + T). 1991 Mathematics Subject Classification: 11F67,11F66, 11F33, 11F30     

Flat Cyclotomic Polynomials of Order Three

A cyclotomic polynomial _n is said to be of order 3 if n = pqrfor three distinct odd primes p, q, and r. We establish theexistence of an infinite family of such polynomials whose coefficientsdo not exceed 1 in modulus. 2000 Mathematics Subject Classification11B83, 11C08.     

A New Lower Bound for the L1 Mean of the Exponential Sum with the MoBius Function

The L¹ means of various exponential sums with arithmeticallyinteresting coefficients have been investigated in many recentpapers. For example, Balog and Perelli proved in [1] that for a suitable positive number c.The method of proving the lower bound in [1] is rather flexibleand can work well with many multiplicative functions in placeof µ(n), the Möbius function, whose Dirichlet serieshave a suitable expression by the Riemann -function. In this short note we improve on the above lower bound. 1991Mathematics Subject Classification 11L03, 42A70.     

Linear Equations in Zp

A lower and an upper bound are proved for the maximum size ofa subset of Z/pZ containing no solutions of a fixed linear equation.2000 Mathematics Subject Classification 11B50, 11B75, 11P99.     

On A Property Of Minimal Zero-Sum Sequences And Restricted Sumsets

Let G be an additively written abelian group, and let S be asequence in G \ {0} with length |S| 4. Suppose that S is aproduct of two subsequences, say S = BC, such that the elementg + h occurs in the sequence S whenever g.h is a subsequenceof B or of C. Then S contains a proper zero-sum subsequence,apart from some well-characterized exceptional cases. This resultis closely connected with restricted set addition in abeliangroups. Moreover, it solves a problem on the structure of minimalzero-sum sequences, which recently occurred in the theory ofnon-unique factorizations. 2000 Mathematics Subject Classification11B50, 11B75, 11P99.     

Properties of Higher-Dimensional Shintani Generating Functions and Cocycles on Pgl3(Q)

In an earlier paper the second author used the formal, algebraicproperties of 2-dimensional Shintani generating functions toconstruct a 1-cocycle on PGL₂{Q}. We aim to generalise theseresults by using such functions in dimension n to obtain an(n–1)-cocycle on PGL_n{Q}, presumably related to the Bernoulliand Eisenstein cocycles of R. Sczech. By improving our methodswe achieve this goal for n=3. For n>3 we encounter obstaclesrelated to degenerate configurations of hyperplanes in n-space.Nevertheless, we obtain partial results closely connected toreciprocity laws for certain n-dimensional Dedekind sums. 1991Mathematics Subject Classification: 11F20, 11F75.     

Long Arithmetic Progressions in Sum-Sets and the Number x-Sum-Free Sets

In this paper we obtain optimal bounds for the length of thelongest arithmetic progression in various kinds of sum-sets.As an application, we derive a sharp estimate for the numberof sets A of residues modulo a prime n such that no subsum ofA equals x modulo n, where x is a fixed residue modulo n. 2000Mathematics Subject Classification 05A16, 11B25, 11P32.     

The Distribution of the Summatory Function of the Mobius Function

The summatory function of the Möbius function is denotedM(x). In this article we deduce conditional results concerningM(x) assuming the Riemann hypothesis and a conjecture of Gonekand Hejhal on the negative moments of the Riemann zeta function.Assuming these conjectures, we show that M(x), when appropriatelynormalized, possesses a limiting distribution, and also thata strong form of the weak Mertens conjecture is true. Finally,we speculate on the lower order of M(x) by studying the constructeddistribution function. 2000 Mathematics Subject Classification11M26, 11N56.     

Semisimple Modules for Finite Groups of Lie Type

Let k be an algebraically closed field of characteristic p >0, and let G be a connected, reductive algebraic group overk. In [8] and [11], conditions on the dimension of rationalG modules were seen to imply semisimplicity of these modules.In [8], certain of these conditions were extended to cover thefinite groups of Lie type. In this paper, we extend some ofthe results of [11] to cover these finite Lie type groups. Themain such extension is the following result.     

Nest Representations of Directed Graph Algebras

This paper is a comprehensive study of the nest representationsfor the free semigroupoid algebra L_G of a countable directedgraph G as well as its norm-closed counterpart, the tensor algebraT⁺(G). We prove that the finite-dimensional nest representations separatethe points in L_G, and a fortiori, in T⁺(G). The irreduciblefinite-dimensional representations separate the points in L_Gif and only if G is transitive in components (which is equivalentto being semisimple). Also the upper triangular nest representationsseparate points if and only if for every vertex x T(G) supportinga cycle, x also supports at least one loop edge. We also study faithful nest representations. We prove that L_G(or T⁺(G) admits a faithful irreducible representation if andonly if G is strongly transitive as a directed graph. More generally,we obtain a condition on G which is equivalent to the existenceof a faithful nest representation. We also give a conditionthat determines the existence of a faithful nest representationfor a maximal type N nest. 2000 Mathematics Subject Classification47L80, 47L55, 47L40.     

Formal Groups of Building Blocks Completely Defined Over Finite Abelian Extensions of Q

Let C be an elliptic curve defined over Q. We can associatetwo formal groups with C: the formal group (X, Y) determinedby the formal completion of the Néron model of C overZ along the zero section, and the formal group F_L(X, Y) of theL-series attached to l-adic representations on C of the absoluteGalois group of Q. Honda shows that F_L(X, Y) is defined overZ, and it is strongly isomorphic over Z to (X, Y). In this paperwe give a generalization of the result of Honda to buildingblocks over finite abelian extensions of Q. The difficulty isto define new matrix L-series of building blocks. Our generalizationcontains the generalization of Deninger and Nart to abelianvarieties of GL₂-type. It also contains the generalization ofour previous paper to Q-curves over quadratic fields. 2000 MathematicsSubject Classification 11G10 (primary), 11F11 (secondary).