Cosmological constraints on thermal relic axions and axion-like particles

Cosmological precision data can be used to set very strict constraints on Axions and Axion-like particles (ALPs) produced thermally in the big bang. We briefly review the known bounds and propose two new constraints for Axions and ALPs decaying in the early universe, based upon the concomitant dilution of baryon and neutrino densities, using WMAP7 and other cosmological data.Comment: 4 pages, 4 figures. To appear in the proceedings of 7th Patras Workshop on Axions, WIMPs and WISPs, Mykonos, Greece, 26 June - 1 July 2011 and of TAUP 2011, Munich, Germany, 5 - 9 September 201

Hidden Photons from the Sun

A brief account of the phenomenon of photon oscillations into sub-eV mass hidden photons is given and used to estimate the flux and properties of these hypothetical particles from the Sun. A new generation of dedicated helioscopes, the Solar Hidden Photon Search (SHIPS) in the Hamburg Observatory amongst them, will cover a vast region of parameter space.Comment: 4 pages, contribution to 6th Patras Workshop on Axions, WIMPs and WISPs, Zurich University, Switzerland, 5-9 July 201

Market versus policy Europeanisation: has an imbalance grown over time? Bruegel Policy Contribution Issue #1 January 2020

This Policy Contribution tests the hypothesis that an imbalance has grown in Europe over the last few decades because markets have integrated to a greater extent than Europeanlevel policymaking, potentially creating difficulties for the democratic process in managing the economy. This hypothesis has been put forward by several authors but not so far tested empirically. To evaluate the process of European market integration – or market Europeanisation – over the last few decades, we assess intra-European trade and intra-European capital flows. Any estimate of policy integration, or Europeanisation, meanwhile, is fraught with difficulties and only proxies can be measured. Our preferred proxy is the number of employees of the European institutions and agencies relative to the aggregate number of public employees in national administrations in the European Union. The assumption is that European public employees generate, implement and oversee European policies and thus their relative number is a proxy for the development of European policies. An alternative indicator of policy Europeanisation is the relative frequency of European Union news in major national media outlets, as a proxy for the relevance to the public of European policies. Our results show that, measured by our proxies, policy Europeanisation has developed more rapidly than market Europeanisation, measured on the basis of both trade and capital flows. It is however also noted that the relative number of public employees has outpaced the relative frequency of European Union news in the media, possibly indicating a technocratic slant in policy Europeanisation. Further research could test the robustness of our results, in particular by using other measures of policy Europeanisation, such as the impact of European legislation on national laws and regulations

Characterization of local observables in integrable quantum field theories

Integrable quantum field theories in 1+1 dimensions have recently become amenable to a rigorous construction, but many questions about the structure of their local observables remain open. Our goal is to characterize these local observables in terms of their expansion coefficients in a series expansion by interacting annihilators and creators, similar to form factors. We establish a rigorous one-to-one characterization, where locality of an observable is reflected in analyticity properties of its expansion coefficients; this includes detailed information about the high-energy behaviour of the observable and the growth properties of the analytic functions. Our results hold for generic observables, not only smeared pointlike fields, and the characterizing conditions depend only on the localization region - we consider wedges and double cones - and on the permissible high energy behaviour.Comment: minor changes, as to appear in Commun. Math. Phys.; 39 pages, 4 figures, 1 vide

A Characterization Theorem for Local Operators in Factorizing Scattering Models

In quantum field theory, the rigorous construction of local observables in the presence of nontrivial interaction is a crucial problem. In a class of integrable quantum field theories, a very abstract existence proof has recently been given by Lechner. We give an explicit characterization of these local observables in terms of the properties of the coefficient functions in an expansion by interacting creators and annihilators. Some results on the operator domains of these local observables are given. Using these, we constructed explicit examples of local observables in the quantum Ising model.Comment: Ph.D. thesis, 169 pages, 11 figure