Explaining External Support for Insurgent Groups

AbstractMany rebel organizations receive significant assistance from external governments, yet the reasons why some rebels attract foreign support while others do not is poorly understood. We analyze factors determining external support for insurgent groups from a principal-agent perspective. We focus on both the supply side, that is, when states are willing to support insurgent groups in other states, and the demand side, that is, when groups are willing to accept such support, with the conditions that this may entail. We test our hypotheses using new disaggregated data on insurgent groups and foreign support. Our results indicate that external rebel support is influenced by characteristics of the rebel group as well as linkages between rebel groups and actors in other countries. More specifically, we find that external support is more likely for moderately strong groups where support is more likely to be offered and accepted, in the presence of transnational constituencies, international rivalries, and when the government receives foreign support.</jats:p

The cohomology of the Grassmannian is a glngl_n-module

The integral singular cohomology ring of the Grassmann variety parametrizing r-dimensional subspaces in the n-dimensional complex vector space is naturally an irreducible representation of the Lie algebra gl n ðZÞ of all the n n matrices with integral entries. The simplest case, r 1⁄4 1, recovers the well known fact that any vector space is a module over the Lie algebra of its own endomorphisms. The other extremal case, r 1⁄4 ∞; corresponds to the bosonic vertex representation of the Lie algebra gl ∞ ðZÞ on the polynomial ring in infinitely many indeterminates, due to Date, Jimbo, Kashiwara and Miwa. In the present article we provide the structure of this irreducible representation explicitly, by means of a distinguished Hasse-Schmidt derivation ation on an exterior algebra, borrowed from Schubert Calculus

The Cohomology of the Grassmannian is a glngl_n-module

The integral singular cohomology ring of the Grassmann variety parametrizing $r$-dimensional subspaces in the $n$-dimensional complex vector space is naturally an irreducible representation of the Lie algebra of all the $n\times n$ matrices with integral entries. Using the notion of Schubert derivation, a distinguished Hasse-Schmidt derivation on an exterior algebra, we describe explicitly such a representation, indicating its relationship with the celebrated bosonic vertex representation of the Lie algebra of infinite matrices due to Date, Jimbo, Kashiwara and Miwa.Comment: 16 pages, no figures, comments welcome at any tim

Um algoritmo de fatoraç˜ao dos n´umeros inteiros usando curvas el´ıpticas

A teoria de curvas el´ıpticas envolve uma bela mistura de ´algebra, geometria, an´alise e teoria dos n´umeros. O objetivo principal deste texto ´e apresentar uma introduc¸˜ao a essa teoria numa maneira acess´ıvel aos alunos de graduac¸˜ao e aplic´a-la num dos problemas mais familiares da aritm´etica dos inteiros: a fatoraç˜ao em primos

Fighting at Home, Fighting Abroad

Although research on conflict has tended to separately study interstate conflict and civil war, states experiencing civil wars are substantially more likely to become involved in militarized disputes with other states. Scholars have typically focused on opportunistic attacks or diversionary wars to explain this domestic–international conflict nexus. The authors argue that international disputes that coincide with civil wars are more often directly tied to the issues surrounding the civil war and emphasize intervention, externalization, and unintended spillover effects from internal conflict as important sources of international friction. They empirically demonstrate that civil wars substantially increase the probability of disputes between states. An analysis of conflict narratives shows that the increased risk of interstate conflict associated with civil wars is primarily driven by states' efforts to affect the outcome of the civil war through strategies of intervention and externalization and not by an increase in conflicts over unrelated issues. </jats:p

A Slippery Slope: The Domestic Diffusion of Ethnic Civil War

Why do most civil wars occur in a relatively small number of countries? We answer this question by analyzing how civil wars diffuse in multiethnic states. Our theory outlines two motivation and two opportunity mechanisms that trigger additional ethnic rebellions in the same state. First, ongoing civil wars motivate members of other ethnic groups to mobilize in reaction to the negative externalities of nearby conflict. Second, ethnic groups emulate nearby rebel groups as a means of addressing preexisting grievances. Third, fighting multiple civil wars drains state capacity, opening the door for additional challengers to rebel against the government. Finally, long-lasting civil wars signal that the state is unable to defeat active rebels, thus creating incentives for new challengers to take up arms. We test our mechanisms in all multiethnic states with a history of armed conflict between 1946 and 2006. Using Geographic Information Systems, we construct overlap and minimum distance measures between ethnic groups’ settlement patterns and conflict zones. Our statistical analysis indicates that new ethnic civil war onsets are more likely in the vicinity of ongoing armed conflicts. Ethnic civil wars also diffuse as governments face an increasing number of rebels and longer rebellions

Congruência Por Corte e Terceiro Problema de Hilbert

http://dx.doi.org/10.5902/2179460X14375Given two polygons with equal areas, one can decompose one of them into a finite number of polygons and rebuild another. This fact is known as the theorem of Bolyai-Gerwien. It is natural to ask whether this theorem is true for polyhedra with equal volumes. This question originally proposed by Bolyai and Gauss in 1844 and then by Hilbert as the Third Problem in his famous list of 23 problems, was negatively answered by Max Dehn in 1902 for polyhedra in three dimension. The main objective of this paper is to present the proof of Dehn. This article has two main parts. The first one is devoted to the concept of area: we will briefly review involving some historical facts to his formalism in geometry and prove the theorem of Bolyai-Gerwien. In the second part we will see how the concept of area and its properties can be interpreted in Euclidean space of dimension three. The main result is the theorem of Dehn-Hadwiger which is crucial to solve the problem of Hilbert for polyhedra.Dados dois polígonos com áreas iguais, é possível decompor um deles em um número finito de polígonos e reconstruir o outro. Esse fato é conhecido como teorema de Bolyai-Gerwien. É natural perguntarmos se este teorema é válido para poliedros com volumes iguais. Essa pergunta inicialmente proposta por Bolyai e Gauss, em 1844, e depois pelo Hilbert como o Terceiro Problema na sua famosa lista de 23 problemas, foi respondida negativamente por Max Dehn, em 1902, para poliedros em dimensão três. Nosso objetivo principal é apresentar a prova de Dehn. Este artigo possui duas partes principais. A primeira é dedicada ao conceito de área: faremos uma breve revisão envolvendo alguns fatos históricos até seu formalismo na geometria e provaremos o teorema de Bolyai-Gerwien. Na segunda parte veremos como o conceito de área e suas propriedades podem ser interpretados no espaço euclidiano de dimensão três. O resultado principal é o teorema de Dehn-Hadwiger que é fundamental para resolver o problema de Hilbert para poliedros

A House Divided: Threat Perception, Regime Factionalism and Repression in Africa

The Ohio State University Mershon Center for International Security StudiesWhy do governments in Africa repress certain contentious challenges but not others? This study adopts a blended approach to studying repression by taking seriously both the characteristics of contentious events as well as nature of the regime in power. We argue that the more threatening a movement is — as measured by the use of violence, opposition demands, and targets — the more likely the state is to use repressive force. However, we relax the assumption that the state is a unitary actor, and allow for the preferences of state leaders and of the security forces to diverge when it comes to carrying out repressive policies. Countries with a history of factionalism in their security forces face an additional challenge: orders to crack down on protesters, rioters, strikers, etc., may not be followed or could even cause police and military forces to defect. We argue this potential is greatest when the challenge is has ethnoreligious aims. We test these propositions using the Social Conflict in Africa Database, and find significant support for our core theoretical conjecture: regimes with a history of past military factionalism are generally less likely to use repression. Such regimes are especially unwilling to repress ethnoreligiously based, ascriptive movements. These results are robust to several estimators that address the hierarchical nature of the event data. These findings demonstrate the benefits of a blended, event-based approach to studying state repression.Mershon Center for International Security StudiesEvent Web Page, Streaming Video, Event Photo

Civil war and U.S. foreign intervention

We study how foreign interventions affect civil war around the world. In an infinitely repeated game we combine a gambling for resurrection mechanism for the influencing country with the canonical bargaining model of war in the influenced country to micro-found sudden shifts in power among the domestic bargaining partners, which are known to lead to war due to commitment problems. We test two of our model predictions that allow us to identify the influence of foreign intervention on civil war incidence: (i) civil wars around the world are more likely under Republican governments and (ii) the probability of civil wars decreases with the U.S. presidential approval rates. These results withstand several robustness checks and, overall, suggest that foreign influence is a sizable driver of domestic conflict