Let [ ]P2,p (where 2 < p) be the class of all finite nilpotent groups of class 2 and of exponent p with an additional predicate for a subgroup of the centre that contains the commutator subgroup. The Fraïssé limit D of this class exists. Non-forking is described for Th(D).

Let V be a commutative valuation domain of arbitrary Krull-dimension (rank), with quotient field F, and let K be a finite Galois extension of F with group G, and S the integral closure of V in K. If, in the crossed product algebra K [midast ] G, the 2-cocycle takes values in the group of units of S, then one can form, in a natural way, a ‘crossed product order’ S [midast ] G ⊆ K [midast ] G. In the light of recent results by H. Marubayashi and Z. Yi on the homological dimension of crossed products, this paper discusses necessary and/or sufficient valuation-theoretic conditions, on the extension K/F, for the V-order S [midast ] G to be semihereditary, maximal or Azumaya over V.

The most natural candidates to the definition of equisingularity of germs of complex space curves are discussed, showing that they coincide in the case of Lagrangean curves (projectivizations of conic Lagrangean varieties of a symplectic manifold of dimension four).

We give here a detailed description of the Brill–Noether loci of stable vector bundles of slope 2 on a smooth projective curve, which is assumed to be nonhyperelliptic.

We prove the existence of a power series having radius of convergence 0, whose partial sums have universal approximation properties on any compact set with connected complement that is contained in a finite union of circles centred at 0 and having rational radii, but do not have such properties on any compact set with nonempty interior. This relates to a theorem of A. I. Seleznev.

An example is constructed of a manifold for which two quadratic forms corresponding to the fourth-order invariant operators are not equivalent.

Let p(n) denote the ordinary partition function. Subbarao conjectured that in every arithmetic progression r (mod t) there are infinitely many integers N ≡ r (mod t) for which p(N) is even, and infinitely many integers M ≡ r (mod t) for which p(M) is odd. We prove the conjecture for every arithmetic progression whose modulus is a power of 2.

This paper introduces a stratification of the variety of modules of a fixed dimension over a finite-dimensional algebra. For a large and interesting class of algebras, called subfinite, this stratification is used to compute the dimension of this variety and give bounds on the number of its irreducible components.

Recall that if S is a class of groups, then a group G is residually-S if, for any element 1 ≠ g ∈ G, there is a normal subgroup N of G such that g ∉ N and G/N ∈ S. Let Λ be a commutative Noetherian local pro-p ring, with a maximal ideal M. Recall that the first congruence subgroup of SLd(Λ) is: SL1d(Λ) = ker (SLd(Λ) → SLd(Λ/M)).

Let K ⊆ ℕ. We define SΛ(K) = ∪d∈K{open subgroups of SL1d(Λ)}. We show that if K is infinite, then for Λ = [ ]p[[t]] and for Λ = ℤp a finitely generated non-abelian free pro-p group is residually-SΛ(K). We apply a probabilistic method, combined with Lie methods and a result on random generation in simple algebraic groups over local fields. It is surprising that the case of zero characteristic is deduced from the positive characteristic case.

For every infinite cardinal κ, we construct a primitive permutation group which has a finite suborbit paired with a suborbit of size κ. This answers a question of Peter M. Neumann.

It is shown that a hypercentral group that has all subgroups subnormal and every non-nilpotent subgroup of bounded defect is nilpotent. As a consequence, a hypercentral group of length at most ω in which every subgroup is subnormal is nilpotent.

Consider the following problem: given complex numbers a1, …, an, find an L∞ function f of minimum norm whose Fourier coefficients ck(f) are equal to ak for k between 0 and n. We show the uniqueness of this function, and we estimate its norm. The operator-valued case is also discussed.

Let M be a geometrically finite pinched negatively curved Riemannian manifold with at least one cusp. The asymptotics of the number of geodesics in M starting from and returning to a given cusp, and of the number of horoballs at parabolic fixed points in the universal cover of M, are studied in this paper. The case of SL(2, ℤ), and of Bianchi groups, is developed.

The quantum stochastic differential equation dkt = kt ∘ θαβdΛβα(t) is considered on a unital C*-algebra, with separable noise dimension space. Necessary conditions on the matrix of bounded linear maps θ for the existence of a completely positive contractive solution are shown to be sufficient. It is known that for completely positive contraction processes, k satisfies such an equation if and only if k is a regular Markovian cocycle. ‘Feller’ refers to an invariance condition analogous to probabilistic terminology if the algebra is thought of as a non-commutative topological space.

Nathan Jacobson, who died on 5 December 1999, was an outstanding algebraist, whose work on almost all aspects of algebra was of fundamental importance, and whose writings will exercise a lasting influence. He had been an honorary member of the Society since 1972.

Nathan Jacobson (later known as ‘Jake’ to his friends) was born in Warsaw (in what he describes as the ‘Jewish ghetto’) on 5 October 1910 (through an error some documents have the date 8 September); he was the second son of Charles Jacobson (as he would be known later) and his wife Pauline, née Rosenberg. His family emigrated to the USA during the First World War, first to Nashville, Tennessee, where his father owned a small grocery store, but they then settled in Birmingham, Alabama, where Nathan received most of his schooling. Later the family moved to Columbus, Mississippi, but the young Nathan entered the University of Alabama in 1926 and graduated in 1930. His initial aim was to follow an uncle and obtain a degree in law, but at the same time he took all the (not very numerous) mathematics courses, in which he did so well that he was offered a teaching assistantship in mathematics in his junior (3rd) year. This marked a turning point; he now decided to major in mathematics and pursue this study beyond College. During his final year at Alabama he applied for admission and financial aid to three top graduate schools in the country: Princeton, Harvard and Chicago. He was awarded a research assistantship at Princeton; after the first year he was appointed a part-time instructor for two years, and during his fourth year he was appointed a Procter Fellow. The stipend was enough to enable him to make a grand tour of Europe by car in 1935, in the company of two Princeton fellow-students at the time: H. F. Bohnenblust and Robert J. Walker.