Comenius University in Bratislava

About: Comenius University in Bratislava is a education organization based out in Bratislava, Slovakia. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 9911 authors who have published 20523 publications receiving 439137 citations.

FCC-hh: The Hadron Collider

Abstract: Particle physics has arrived at an important moment of its history. The discovery of the Higgs boson, with a mass of 125 GeV, completes the matrix of particles and interactions that has constituted the “Standard Model” for several decades. This model is a consistent and predictive theory, which has so far proven successful at describing all phenomena accessible to collider experiments. However, several experimental facts do require the extension of the Standard Model and explanations are needed for observations such as the abundance of matter over antimatter, the striking evidence for dark matter and the non-zero neutrino masses. Theoretical issues such as the hierarchy problem, and, more in general, the dynamical origin of the Higgs mechanism, do likewise point to the existence of physics beyond the Standard Model. This report contains the description of a novel research infrastructure based on a highest-energy hadron collider with a centre-of-mass collision energy of 100 TeV and an integrated luminosity of at least a factor of 5 larger than the HL-LHC. It will extend the current energy frontier by almost an order of magnitude. The mass reach for direct discovery will reach several tens of TeV, and allow, for example, to produce new particles whose existence could be indirectly exposed by precision measurements during the earlier preceding e+e– collider phase. This collider will also precisely measure the Higgs self-coupling and thoroughly explore the dynamics of electroweak symmetry breaking at the TeV scale, to elucidate the nature of the electroweak phase transition. WIMPs as thermal dark matter candidates will be discovered, or ruled out. As a single project, this particle collider infrastructure will serve the world-wide physics community for about 25 years and, in combination with a lepton collider (see FCC conceptual design report volume 2), will provide a research tool until the end of the 21st century. Collision energies beyond 100 TeV can be considered when using high-temperature superconductors. The European Strategy for Particle Physics (ESPP) update 2013 stated “To stay at the forefront of particle physics, Europe needs to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next Strategy update”. The FCC study has implemented the ESPP recommendation by developing a long-term vision for an “accelerator project in a global context”. This document describes the detailed design and preparation of a construction project for a post-LHC circular energy frontier collider “in collaboration with national institutes, laboratories and universities worldwide”, and enhanced by a strong participation of industrial partners. Now, a coordinated preparation effort can be based on a core of an ever-growing consortium of already more than 135 institutes worldwide. The technology for constructing a high-energy circular hadron collider can be brought to the technology readiness level required for constructing within the coming ten years through a focused R&D programme. The FCC-hh concept comprises in the baseline scenario a power-saving, low-temperature superconducting magnet system based on an evolution of the Nb3Sn technology pioneered at the HL-LHC, an energy-efficient cryogenic refrigeration infrastructure based on a neon-helium (Nelium) light gas mixture, a high-reliability and low loss cryogen distribution infrastructure based on Invar, high-power distributed beam transfer using superconducting elements and local magnet energy recovery and re-use technologies that are already gradually introduced at other CERN accelerators. On a longer timescale, high-temperature superconductors can be developed together with industrial partners to achieve an even more energy efficient particle collider or to reach even higher collision energies.The re-use of the LHC and its injector chain, which also serve for a concurrently running physics programme, is an essential lever to come to an overall sustainable research infrastructure at the energy frontier. Strategic R&D for FCC-hh aims at minimising construction cost and energy consumption, while maximising the socio-economic impact. It will mitigate technology-related risks and ensure that industry can benefit from an acceptable utility. Concerning the implementation, a preparatory phase of about eight years is both necessary and adequate to establish the project governance and organisation structures, to build the international machine and experiment consortia, to develop a territorial implantation plan in agreement with the host-states’ requirements, to optimise the disposal of land and underground volumes, and to prepare the civil engineering project. Such a large-scale, international fundamental research infrastructure, tightly involving industrial partners and providing training at all education levels, will be a strong motor of economic and societal development in all participating nations. The FCC study has implemented a set of actions towards a coherent vision for the world-wide high-energy and particle physics community, providing a collaborative framework for topically complementary and geographically well-balanced contributions. This conceptual design report lays the foundation for a subsequent infrastructure preparatory and technical design phase.

Streamflow trends in Europe: evidence from a dataset of near-natural catchments

Abstract: Streamflow observations from near-natural catch- ments are of paramount importance for detection and at- tribution studies, evaluation of large-scale model simula- tions, and assessment of water management, adaptation and policy options. This study investigates streamflow trends in a newly-assembled, consolidated dataset of near-natural streamflow records from 441 small catchments in 15 coun- tries across Europe. The period 1962-2004 provided the best spatial coverage, but analyses were also carried out for longer time periods (with fewer stations), starting in 1932, 1942 and 1952. Trends were calculated by the slopes of the Kendall-Theil robust line for standardized annual and monthly streamflow, as well as for summer low flow mag- nitude and timing. A regionally coherent picture of annual streamflow trends emerged, with negative trends in southern and eastern regions, and generally positive trends elsewhere. Trends in monthly streamflow for 1962-2004 elucidated po- tential causes for these changes, as well as for changes in hydrological regimes across Europe. Positive trends were found in the winter months in most catchments. A marked shift towards negative trends was observed in April, grad- ually spreading across Europe to reach a maximum extent

Poisson Geometry with a 3-Form Background

Abstract: We study a modification of Poisson geometry by a closed 3-form. Just as for ordinary Poisson structures, these "twisted" Poisson structures are conveniently described as Dirac structures in suitable Courant algebroids. The additive group of 2-forms acts on twisted Poisson structures and permits them to be seen as glued from ordinary Poisson structures defined on local patches. We conclude with remarks on deformation quantization and twisted symplectic groupoids.

The Endogeneity of the Optimum Currency Area Criteria, Intra-industry Trade, and EMU Enlargement

Abstract: 1. INTRODUCTION Countries participating in a currency area face benefits and costs of the common currency. The benefits are directly related to transaction costs in countries' bilateral trade. Therefore, countries with intensive trade relations are likely to gain relatively more from the monetary integration. In addition, Frankel and Rose (1997, 1998) hypothesize that business cycles are also becoming more similar across countries having intensive trade links. This hypothesis is supported by cross-section estimations of the relation between the correlation of business cycles and trade intensity among Organisation for Economic Co-operation and Development (OECD) countries between 1959 and 1993. Moreover, Fatas (1997) and Hochreiter and Winckler (1995) show that a common European business cycle has been emerging as predicted by the endogeneity hypothesis of optimum currency area (OCA) criteria. Nevertheless, there remains considerable doubt whether there is a causal relationship between trade links and the correlation of business cycles in the involved countries. Kose et al. (2003) find only weak evidence for the hypothesis that increased trade and financial flows have increased the synchronization of business cycles. Kenen (2000) notes that the correlation of business cycles may increase with the intensity of trade links between these countries, but he argues that this does not necessarily mean that asymmetric shocks are reduced as well. Moreover, Hughes Hallett and Piscitelli (2001) show that a currency union may increase cyclical convergence, but only if there is already a sufficient symmetry in the shocks and institutional structure across the countries. Their findings thus support Krugman's (1993) discussion of the implications from the U.S. currency union for the Economic and Monetary Union (EMU) in Europe. In Krugman's view, trade liberalization facilitates increased specialization according to comparative advantage of countries and possibly a divergence of business cycles in the EMU. Furthermore, Frankel and Rose's work lacks a stronger relation to trade structure, (1) which should also explain the similarity of business cycles, although they use intraindustry trade (IIT) as an argument. In particular, the effects of trade on the convergence of business cycles depend on the degree of industrial specialization induced by the integration. Indeed, Helpman (1987) and Hummels and Levinsohn (1995) find that trade specialization plays a lesser role for trade among developed economies. Thus a majority of trade is observed within the same industries (the so called IIT). This should imply increasing correlation of business cycles between these countries. Therefore, this article tests the OCA endogeneity using bilateral levels of IIT between OECD countries in the 1990s. It is shown that IIT induces the convergence of business cycles between trading partners, but there is no direct relation between business cycle and trade intensity. As a result, the OCA endogeneity hypothesis is confirmed. However, this finding also underlines the role of the specialization in trade. Finally, the article asks whether the Central and Eastern European countries (CEECs) should introduce the euro as soon as possible after accession to the European Union (EU), or whether they should do so at a later stage. This question is addressed by applying the endogeneity hypothesis of OCA criteria to ten transition economies (Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Slovakia, and Slovenia). This article applies the relation between the degree of trade integration, the shares of IIT, and the convergence in business cycles to CEECs and EU countries to predict the degree of business cycle harmonization of CEECs with EU countries in the medium term. This approach reflects the Lucas critique insofar as it considers possible structural changes during the accession of the CEECs to the EU and the EMU. …

Performance of the ATLAS Trigger System in 2010

Abstract: Proton-proton collisions at root s = 7 TeV and heavy ion collisions at root(NN)-N-s = 2.76 TeV were produced by the LHC and recorded using the ATLAS experiment's trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and B meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented.