Dipole operator constraints on composite Higgs models

Flavour- and CP-violating electromagnetic or chromomagnetic dipole operators in the quark sector are generated in a large class of new physics models and are strongly constrained by measurements of the neutron electric dipole moment and observables sensitive to flavour-changing neutral currents, such as the $B\to X_s\gamma$ branching ratio and $\epsilon'/\epsilon$. After a model-independent discussion of the relevant constraints, we analyze these effects in models with partial compositeness, where the quarks get their masses by mixing with vector-like composite fermions. These scenarios can be seen as the low-energy limit of composite Higgs or warped extra dimensional models. We study different choices for the electroweak representations of the composite fermions motivated by electroweak precision tests as well as different flavour structures, including flavour anarchy and $U(3)^3$ or $U(2)^3$ flavour symmetries in the strong sector. In models with "wrong-chirality" Yukawa couplings, we find a strong bound from the neutron electric dipole moment, irrespective of the flavour structure. In the case of flavour anarchy, we also find strong bounds from flavour-violating dipoles, while these constraints are mild in the flavour-symmetric models.Comment: 30 pages, 2 figures, 11 tables. v3: Misprints in table 8 corrected. Numerics and conclusions unchange

Germany's preferences on the freedom of movement provisions of the Ankara Agreement: the Wirtschaftswunder and opportunity and effort of Turkish diplomacy

Why did Germany support provisions on freedom of movement for Turkish workers in the Association Agreement between the European Economic Community (EEC) and Turkey, which was concluded in 1963? This is puzzling given that Germany was fervently opposed to other common EU measures on legal economic migration since immigration policy was communitarized by the Amsterdam Treaty in 1999. The papers test two hypotheses. First, that the a positive economic situation induces the German government to support common EU measures as in periods of strong growth Germany has more open immigration policies and there is a positive relationship between open national immigration policies and support for common EU measures. Second, a sending country (or a group of sending countries) needs to exert diplomatic pressure on the German government in order for it to support common EU measures on legal economic migration. For this to be successful there need to be two conditions in place, the sending country must have the opportunity to exert influence, due to strong historical ties with Germany or being important for geo-political reasons, and frame the need for common EU measures on legal migration in an effective manner. The hypotheses are confirmed for the case of Turkey and the Ankara Agreement and are used to assemble a theoretically eclectic and generally applicable framework able to explain Germany’s support for common EU measures on legal economic migration

A primal Barvinok algorithm based on irrational decompositions

We introduce variants of Barvinok's algorithm for counting lattice points in polyhedra. The new algorithms are based on irrational signed decomposition in the primal space and the construction of rational generating functions for cones with low index. We give computational results that show that the new algorithms are faster than the existing algorithms by a large factor.Comment: v3: New all-primal algorithm. v4: Extended introduction, updated computational results. To appear in SIAM Journal on Discrete Mathematic

Vacuum Friction

We know that in empty space there is no preferred state of rest. This is true both in special relativity but also in Newtonian mechanics with its associated Galilean relativity. It comes as something of a surprise, therefore, to discover the existence a friction force associated with spontaneous emission. he resolution of this paradox relies on a central idea from special relativity even though our derivation of it is non-relativistic. We examine the possibility that the physics underlying this effect might be explored in an ion trap, via the observation of a superposition of different mass states.Comment: 8 pages, 2 figures. Published in Journal of Modern Optics on 14 September 2017. Version 2 with a corrected typo on page

The Röntgen interaction and forces on dipoles in time-modulated optical fields

The Röntgen term is an often neglected contribution to the interaction between an atom and an electromagnetic field in the electric dipole approximation. In this work we discuss how this interaction term leads to a difference between the kinetic and canonical momentum of an atom which, in turn, leads to surprising radiation forces acting on the atom. We use a number of examples to explore the main features of this interaction, namely forces acting against the expected dipole force or accelerations perpendicular to the beam propagation axis

Beyond Crisis Management: The Path Towards an Effective, Pro-active and Fair European Refugee Policy. Bertelsmann Study

Europe urgently needs an effective, pro-active and fair refugee policy. Short-sighted policy-making and a narrow focus on what seemed to be in the immediate national interests have led to a conglomerate of European refugee policies. These policies are clearly ineffective and resulted in a large and partially uncontrolled refugee movement to and within Europe in 2015. Refugee flows to Europe are unlikely to subside soon, as many conflicts persist and the average duration of protracted refugee situations worldwide is on the rise. In a reaction to these circumstances, the European Com-mission has proposed a number of initiatives to reform the Common European Asylum System (CEAS). Consensus is more likely on the introduction of restrictions and sanctions rather than, for example, fair distribution systems or pooling sovereignty on the EU level by establishing a strong EU Agency of Asylum. Yet, especially pro-active solutions that meet Europe’s humanitarian responsi-bilities are necessary. The paper puts forward policy-recommendations for a paradigm-shift from reactive to pro-active refugee policies. The overarching objective is to create further legal channels for refugees to seek protection in Europe. Measures include both national and EU-policies and are supposed to pave the way to a sustainable and coherent European refugee policy. The policy recommendations are clus-tered in five overarching themes: create safe passages to protection, improve national asylum processing and integration systems, establish further legal pathways for mixed migration, enable protection in the region of origin, and tackle the root causes of forced migration through a sustainable foreign, economic and trade policy. Finally, it has to be stressed that only if we can restore Europe’s political will to manage refugee flows together, there will be sustainable solutions in sight. Regular dialogue taking into account the different resources and histories of the countries are the way forward. If member states can incrementally alight their different national policies, a comprehensive European refugee policy may follow. Given the current political differences amongst member states, this will be a lengthy process – but certainly worth the effort