Let H be a countable infinite homogeneous relational structure. If H is indivisible then it is weakly indivisible and if it is weakly indivisible then it is age indivisible. There are examples of countable infinite homogeneous structures which are weakly indivisible but not indivisible. It is a natural question to ask for examples of countable age indivisible homogenous structures which are not...

Geoffrey Grimmett and Svante Janson Abstra t. Pick n points independently at random in R2 , according to a prescribed probability measure μ, and let ∆ 1 ≤ ∆ 2 ≤ . . . be the areas of the n 3 triangles thus formed, in non-decreasing order. If μ is absolutely continuous with respect to Lebesgue measure, then, under weak conditions, the set {n∆ i : i ≥ 1} converges as n → ∞ to a Poisson process wi...

6 Lie Derivatives and the Commutator Revisited 21 6.1 Integral Curves . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.2 Congruence of Curves . . . . . . . . . . . . . . . . . . . . . . . 21 6.3 The Commutator Revisited: A Geometric Interpretation . . . 22 6.4 Lie Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.5 Lie Derivatives of a Function . . . . . . . . . . . ....

After dimensional reduction to three dimensions, the lowest order effective actions for pure gravity, M-theory and the Bosonic string admit an enhanced symmetry group. In this paper we initiate study of how this enhancement is affected by the inclusion of higher derivative terms. In particular we show that the coefficients of the scalar fields associated to the Cartan subalgebra are given by we...

This paper illustrates the notion of a Cartan subalgebra in a C*algebra through a number of examples and counterexamples. Some of these examples have a geometrical flavour and are related to orbifolds and nonHausdorff manifolds.

In this paper we study the notion of strong non-reflection, and its contrapositive weak reflection. We say θ strongly non-reflects at λ iff there is a function F : θ −→ λ such that for all α < θ with cf(α) = λ there is C club in α such that F 1 C is strictly increasing. We prove that it is consistent to have a cardinal θ such that strong non-reflection and weak reflection each hold on an unboun...

where Δpu = div(|∇u|p−2∇u) is the p-Laplacian of u with 1 < p < ∞, and λ is a real parameter. Moreover, Ω is a smooth bounded domain in RN , N ≥ 1, whose boundary ∂Ω is made of two disjoint nonempty closed sets Γ1 and Γ2 which are smooth manifolds of dimension N − 1, m and n are weights which may be indefinite and unbounded, ∂/∂ν denotes the exterior normal derivative, and u± = max{±u,0}. The m...

Recently, V.Ginzburg introduced the notion of a principal nilpotent pair (= pn-pair) in a semisimple Lie algebra g [Gi99]. It is a double counterpart of the notion of a regular nilpotent element in g. A pair e = (e1, e2) ∈ g × g is called nilpotent, if [e1, e2] = 0 and there exists a pair h = (h1, h2) of semisimple elements such that [h1, h2] = 0, [hi, ej ] = δijej (i, j ∈ {1, 2}). A pn-pair e ...

We consider the supercircle S equipped with the standard contact structure. The conformal Lie superalgebra K(1) acts on S as the Lie superalgebra of contact vector fields; it contains the Möbius superalgebra osp(1|2). We study the space of linear differential operators on weighted densities as a module over osp(1|2). We introduce the canonical isomorphism between this space and the correspondin...

The purpose of this paper is to study Hom-Lie superalgebras, that is a superspace with a bracket for which the superJacobi identity is twisted by a homomorphism. This class is a particular case of Γ-graded quasi-Lie algebras introduced by Larsson and Silvestrov. In this paper, we characterize Hom-Lie admissible superalgebras and provide a construction theorem from which we derive a one paramete...