The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. ?? 2013 Elsevier B.V. All rights reserved

We report on an extensive test campaign of a prototype version of the QUBIC (Q & U Bolometric Interferometer for Cosmology) instrument, carried out at Astroparticle Physics and Cosmology (APC) in Paris. Exploiting the novel concept called bolometric interferometry, QUBIC is designed to measure the CMB polarization at 150 and 220 GHz from a high altitude site at Alto Chorillo, Argentina. The prototype model called QUBIC Technological Demonstrator (QUBIC-TD) operates in a single frequency band (150 GHz) and with a reduced number of baselines, but it contains all the elements of the QUBIC instrument in its final configuration. The test campaign included measurements of the synthesized beam and of the polarization performance, as well as a verification of the interference fringe pattern. A modulated, frequency-tunable millimetre-wave source was placed in the telescope far-field and was used to simulate a point source. The QUBIC-TD field of view was scanned across the source to produce beam maps. Our measurements confirm the frequency-dependent behaviour of the beam profile, which gives QUBIC the possibility to do spectral imaging. The measured polarization performance indicates a cross-polarization leakage less than 0.6%. We also successfully tested the polarization modulation system, which is provided by a rotating half wave plate. We demonstrate the full mapmaking pipeline using data from this measurement campaign, effectively giving an end-to-end checkout of the entire QUBIC system, including all hardware subsystems, their interfaces, and the software to operate the whole system and run the analysis. Our results confirm the viability of bolometric interferometry for measurements of the CMB polarization.

I argue that there are no physical singularities in space-time. Singular space-time models do not belong to the ontology of the world, because of a simple reason: they are concepts, defective solutions of Einstein's field equations. I discuss the actual implication of the so-called singularity theorems. In remarking the confusion and fog that emerge from the reification of singularities I hope to contribute to a better understanding of the possibilities and limits of the theory of General Relativity.