A very short proof of Forester's rigidity result

The deformation space of a simplicial G-tree T is the set of G-trees which can be obtained from T by some collapse and expansion moves, or equivalently, which have the same elliptic subgroups as T. We give a short proof of a rigidity result by Forester which gives a sufficient condition for a deformation space to contain an Aut(G)-invariant G-tree. This gives a sufficient condition for a JSJ splitting to be invariant under automorphisms of G. More precisely, the theorem claims that a deformation space contains at most one strongly slide-free G-tree, where strongly slide-free means the following: whenever two edges e_1, e_2 incident on a same vertex v are such that G_{e_1} is a subset of G_{e_2}, then e_1 and e_2 are in the same orbit under G_v.Comment: Published by Geometry and Topology at http://www.maths.warwick.ac.uk/gt/GTVol7/paper10.abs.htm

Die EU und der Rückzug des Staates: Eine Genealogie der Neoliberalisierung der europäischen Integration

"Die europäische Integration führt zu einer Schwächung des Staates zugunsten des Marktes." - Diese These bestimmt seit einigen Jahren den EU-Diskurs. Aber kann man wirklich von einer Neoliberalisierung durch die EU sprechen? Und wenn ja, war diese Entwicklung gewollt oder war sie der Logik supranationaler Zusammenarbeit geschuldet? Der Band geht diesen Fragen anhand der europäischen Vorgaben für die nationale Ausgabenpolitik nach. Eine Analyse der Geschichte der Integration seit den Römischen Verträgen zeigt, dass es Alternativen zur heutigen Dominanz neoliberaler Politik gegeben hat - und somit auch wieder geben kann

Manifolds with non-stable fundamental groups at infinity, II

In this paper we continue an earlier study of ends non-compact manifolds. The over-arching goal is to investigate and obtain generalizations of Siebenmann's famous collaring theorem that may be applied to manifolds having non-stable fundamental group systems at infinity. In this paper we show that, for manifolds with compact boundary, the condition of inward tameness has substatial implications for the algebraic topology at infinity. In particular, every inward tame manifold with compact boundary has stable homology (in all dimensions) and semistable fundamental group at each of its ends. In contrast, we also construct examples of this sort which fail to have perfectly semistable fundamental group at infinity. In doing so, we exhibit the first known examples of open manifolds that are inward tame and have vanishing Wall finiteness obstruction at infinity, but are not pseudo-collarable.Comment: Published by Geometry and Topology at http://www.maths.warwick.ac.uk/gt/GTVol7/paper7.abs.htm

Die EU und der Rückzug des Staates

Die europäische Integration führt zu einer Schwächung des Staates zugunsten des Marktes. - Diese These bestimmt seit einigen Jahren den EU-Diskurs. Aber kann man wirklich von einer Neoliberalisierung durch die EU sprechen? Und wenn ja, war diese Entwicklung gewollt oder war sie der Logik supranationaler Zusammenarbeit geschuldet? Der Band geht diesen Fragen anhand der europäischen Vorgaben für die nationale Ausgabenpolitik nach. Eine Analyse der Geschichte der Integration seit den Römischen Verträgen zeigt, dass es Alternativen zur heutigen Dominanz neoliberaler Politik gegeben hat - und somit auch wieder geben kann

“The Least Sexually Confident Women in the World”: International NGOs and the Racialized Politics of Obstetric Fistula

In 2008, Christian author Shannon Ethridge pledged to donate a portion of the sales of her book The Sexually Confident Wife to the medial charity Mercy Ships International. Donations supported the provision of obstetric fistula repair surgeries for West African women who she dubbed “the least sexually confident women in the world.” This thesis asks what conditions occasioned Ethridge’s problematic statement and in so doing engages in a larger examination of evangelical NGO Mercy Ships, its history and contemporary practice, and the racialized, gendered and sexualized politics of fistula repair in international relief and development. First presenting histories related to the development of the international NGO, Christian medical missions to Africa and colonial and imperialist discourses surrounding the “protection” of colonized women, this analysis then turns to widespread donor and media portrayals of obstetric fistula. Staked in racist stereotyping and cultural pathologization, the typical narrative surrounding fistula, as this analysis shows, offers a site of convergence for the agendas of groups one would expect to be on opposite sides of a reproductive health issue, “progressive” feminists and religious conservatives. In this sense, obstetric fistula as a cause du jour reiterates long-standing racialized logics underwriting how colonial and humanitarian discourses have selectively become concerned with the plight of “Other” women for strategic means. In our contemporary context, this thesis argues, obstetric fistula as a cause can be read as a diversionary tactic and moral cover for the effects of neoliberal economic policy in the global south, a site of essential revenue generation for international NGOs and, finally, a sleight of hand that distracts from the unacknowledged conditions of patriarchy at “home.

Diagrammatic Reasoning Skills of Pre-Service Mathematics Teachers

This study attempted to explore a possible relationship between diagrammatic reasoning and geometric knowledge of pre-service mathematics teachers. Diagrammatic reasoning skills, as a sequence of steps from visualization, to interpretation, to formalisms, are at the core of teachers' content knowledge for teaching. However, there is no course in the mathematics curriculum that systematically develops diagrammatic reasoning skills, except Geometry. In the course of this study, a group of volunteers in the last semester of their teacher preparation program were presented with "visual proofs" of certain theorems from high school mathematics curriculum and asked to prove/explain these theorems by reasoning from the diagrams. The results of the interviews were analyzed with respect to the participants' attained van Hiele levels. The study found that participants who attained higher van Hiele levels were more skilled at recognizing visual theorems and "proving" them. Moreover, the study found a correspondence between participants' diagrammatic reasoning skills and certain behaviors attributed to van Hiele levels. However, the van Hiele levels attained by the participants were consistently higher than their diagrammatic reasoning skills would indicate

Plädoyer für eine zukunftsoffene Verfasstheit Europas

The French and Dutch “no” to the European Constitution and the following “period of reflection” offer the opportunity to introduce critical ideas into the discussion on the future of the European Union. For the critics it is not only necessary to excoriate the Constitution, but also to propose alternatives. The authors therefore generate requirements for the contents of a new European Constitution. In a second step concrete alternatives are provided, dealing among others with a democratic way of organizing the European institutions, basic rights as well as economic and social policies. The general aim is to open the Constitution for political processes, which means to minimize the (economic) stipulations for European politics in the Constitution

Globalisierung zwischen Monokultur der Werte und Weltethos

"Die Globalisierung in ihrer derzeitigen Form ist überwiegend ökonomisch geprägt. Die Gefahr, die in einer Vorherrschaft des Subsystems Wirtschaft liegt, ist die einseitige Ausrichtung der Welt auf den Wert des ökonomisch Nützlichen. Davon ausgehend, dass eine solche Monokultur der Werte die Welt aus ihrem notwendigen Gleichgewicht wirft, soll hier aufgezeigt werden, welche Alternative ein globalethischer Diskurs bietet." (Autorenreferat)"Financial and economic globalization increases economic insecurity and social inequality. It bypasses and devalues people's choices, democratic institutions, and sovereign nations responsible for the common good. In their place it puts a logic that is purely economic and 'rational' and only expresses the interests of multinational corporations and (financial) markets. Facing the consequences of this development on values - which are more and more oriented on the economic use or profit - the article shows the alternative of a global ethic which keeps the world in the necessary balance." (author's abstract

Peripheral fillings of relatively hyperbolic groups

A group theoretic version of Dehn surgery is studied. Starting with an arbitrary relatively hyperbolic group $G$ we define a peripheral filling procedure, which produces quotients of $G$ by imitating the effect of the Dehn filling of a complete finite volume hyperbolic 3--manifold $M$ on the fundamental group $\pi_1(M)$. The main result of the paper is an algebraic counterpart of Thurston's hyperbolic Dehn surgery theorem. We also show that peripheral subgroups of $G$ 'almost' have the Congruence Extension Property and the group $G$ is approximated (in an algebraic sense) by its quotients obtained by peripheral fillings. Various applications of these results are discussed.Comment: The difference with the previous version is that Proposition 3.2 is proved for quasi--geodesics instead of geodesics. This allows to simplify the exposition in the last section. To appear in Invent. Mat

Minsky machines and algorithmic problems

This is a survey of using Minsky machines to study algorithmic problems in semigroups, groups and other algebraic systems.Comment: 19 page