Beyond Rainbow-Ladder in bound state equations

In this work we devise a new method to study quark anti-quark interactions beyond simple ladder-exchange that yield massless pions in the chiral limit. The method is based on the requirement to have a representation of the quark-gluon vertex that is explicitly given in terms of quark dressings functions. We outline a general procedure to generate the Bethe-Salpeter kernel for a given vertex representation. Our method allows not only the identification of the mesons' masses but also the extraction of their Bethe-Salpeter wave functions exposing their internal structure. We exemplify our method with vertex models that are of phenomenological interest.Comment: 13 pages, 6 figures; v2: typos corrected, colors improve

The light scalar mesons as tetraquarks

We present a numerical solution of the four-quark Bethe-Salpeter equation for ground-state scalar tetraquarks with J^PC = 0^++. We find that the four-body equation dynamically generates pseudoscalar-meson poles in the Bethe-Salpeter amplitude. The resulting tetraquarks are genuine four-quark states that are dominated by pseudoscalar meson-meson correlations. Diquark-antidiquark contributions are subleading because of their larger mass scale. In the light quark sector, the sensitivity of the tetraquark wave function to the pion poles leads to an isoscalar tetraquark mass M_sigma ~ 350 MeV which is comparable to that of the sigma/f0(500). The masses of its multiplet partners kappa and a0/f0 follow a similar pattern. This provides support for a tetraquark interpretation of the light scalar meson nonet in terms of 'meson molecules'.Comment: 7 pages, 4 figures; version accepted by PL

International organisations and human rights: What direct authority needs for its legitimation

Human rights violations by international organisations (IOs) are a possible side effect of their growing authority. Recent examples are the cases of sexual exploitation by UN peacekeepers and violations caused by IMF austerity measures. In response, IOs increasingly develop safeguards to protect human rights from being violated through their policies to regain legitimacy. We argue that this development can be accounted for by a mechanism we call ‘authority-legitimation mechanism’. We test this theoretical expectation against ten case studies on UN and EU sanctions policies, UN and NATO peacekeeping and World Bank and IMF lending. Next, we demonstrate inductively that the authority-legitimation mechanism can evolve through different pathways, depending on which actors get engaged. We label these pathways legislative institution-building if parliaments in member states put pressure on their governments to campaign for human rights safeguards in IOs, judicial institution-building if courts demand human rights safeguards, like-minded institution-building if civil society organisations, middle powers and IO bodies with little formal power push for human rights safeguards, or anticipatory institution-building if IOs adopt such safeguards from other IOs without having violated human rights themselves. Finally, we argue that which of these pathways are activated and how effective they are depends on specific conditions

US Counterterrorism and the Human Rights of Foreigners Abroad

This book examines why the United States has introduced safeguards that are designed to prevent their counterterrorism policies from causing harm to non-US citizens beyond US territory. It investigates what made US policymakers take steps to "put the gloves back on" through five case studies on the emergence of such safeguards related to the right not to be tortured, the right not to be arbitrarily detained, the right to life (in connection with targeted killing operations), the right to seek asylum (in connection with refugee resettlement), and the right to privacy (in connection with foreign mass surveillance). The book exposes two mechanisms – coercion and strategic learning – which explain why the United States has introduced what the authors refer to as "extraterritorial human rights safeguards", thus demonstrating that the emerging norm that states have human rights obligations towards foreigners beyond their borders constrains policy choices. This book will be of key interest to scholars and students of human rights, counterterrorism, US foreign policy, human rights law, and more broadly to political science and international relations