The borders I crossed

The Mackey Machine for Crossed Products by Regular Groupoids. I

We first describe a Rieffel induction system for groupoid crossed products. We then use this induction system to show that, given a regular groupoid G and a dynamical system (A,G,α), every irreducible representation of A⋊G is induced from a representation of the group crossed product A(u)⋊Su where u ∈ G(0), A(u) is a fibre of A, and Su is a stabilizer subgroup of G.

The category of generalized crossed modules

In the definition of a crossed module $(T,G,rho)$, the actions of the group $T$ and $G$ on themselves are given by conjugation. In this paper, we consider these actions to be arbitrary and thus generalize the concept of ordinary crossed module. Therefore, we get the category ${bf GCM}$, of all generalized crossed modules and generalized crossed module morphisms between them, and investigate som...

Contradictions at the Borders

1 The issue The purpose of this essay is to shed some light on a certain type of sentence, which I call a borderline contradiction. A borderline contradiction is a sentence of the form F a ∧ ¬F a, for some vague predicate F and some borderline case a of F , or a sentence equivalent to such a sentence. For example, if Jackie is a borderline case of 'rich', then 'Jackie is rich and Jackie isn't r...

The Virtuality of Territorial Borders

Open Borders

Article history: Received 6 January 2012 Revised 20 August 2012 Available online 17 October 2012 JEL classification: F16 F22 F66 J61 O15