Simplicity of algebras associated to \'etale groupoids

We prove that the C*-algebra of a second-countable, \'etale, amenable groupoid is simple if and only if the groupoid is topologically principal and minimal. We also show that if G has totally disconnected unit space, then the associated complex *-algebra introduced by Steinberg is simple if and only if the interior of the isotropy subgroupoid of G is equal to the unit space and G is minimal.Comment: The introduction has been updated and minor changes have been made throughout. To appear in Semigroup Foru

A groupoid generalization of Leavitt path algebras

Let G be a locally compact, Hausdorff groupoid in which s is a local homeomorphism and the unit space is totally disconnected. Assume there is a continuous cocycle c from G into a discrete group $\Gamma$. We show that the collection A(G) of locally-constant, compactly supported functions on G is a dense *-subalgebra of C_c(G) and that it is universal for algebraic representations of the collection of compact open bisections of G. We also show that if G is the groupoid associated to a row-finite graph or k-graph with no sources, then A(G) is isomorphic to the associated Leavitt path algebra or Kumjian-Pask algebra. We prove versions of the Cuntz-Krieger and graded uniqueness theorems for A(G)

A groupoid generalisation of Leavitt path algebras

Let G be a locally compact, Hausdorff, étale groupoid whose unit space is totally disconnected.We show that the collection A(G) of locally-constant, compactly supported complex-valued functions on G is a dense ∗-subalgebra of Cc(G) and that it is universal for algebraic representations of the collection of compact open bisections of G. We also show that if G is the groupoid associated to a row-finite graph or k-graph with no sources, then A(G) is isomorphic to the associated Leavitt path algebra or Kumjian–Pask algebra. We prove versions of the Cuntz–Krieger and graded uniqueness theorems for A(G)

Simplicity of algebras associated to étale groupoids

We prove that the full C*-algebra of a second-countable, Hausdorff, etale, amenable groupoid is simple if and only if the groupoid is both topologically principal and minimal. We also show that if G has totally disconnected unit space, then the complex *-algebra of its inverse semigroup of compact open bisections, as introduced by Steinberg, is simple if and only if G is both effective and minimal

Desecuritizar la 'guerra contra las drogas'

This chapter makes use of Colombian-US bilateral relations as a window to trace the evolution of the US-designed ‘war on drugs’, highlighting the role of securitization in the development of counternarcotics activities in Colombia and discussing the process through which the shortcomings of this policy have created opportunities to engage in desecuritization and to design alternative strategies. It explores the principles that have sustained the ‘war on drugs’ and the evolution of Colombian-US relations since 1998, providing an overall assessment of the anti-drug strategy that helps to analyse the possibilities of desecuritization in the light of the Copenhagen school’s securitization theory. Finally, the chapter identifies the challenges that drug policy reform currently faces in Colombia and Latin America more generally