Schwinger Pair Creation of Kaluza-Klein Particles: Pair Creation Without Tunneling

We study Schwinger pair creation of charged Kaluza-Klein (KK) particles from a static KK electric field. We find that the gravitational backreaction of the electric field on the geometry—which is incorporated via the electric KK-Melvin solution—prevents the electrostatic potential from overcoming the rest mass of the KK particles, thus impeding the tunneling mechanism which is often thought of as responsible for the pair creation. However, we find that pair creation still occurs with a finite rate formally similar to the classic Schwinger result, but via an apparently different mechanism, involving a combination of the Unruh effect and vacuum polarization due to the E-field

Values in times of crisis : strategic crisis management in the EU

In a crisis, the fundamental values or, in other words, the functioning of a society is under threat (SAPEA, 2022, p. 38). A difficulty in strategic crisis management is that responses to the situation need to be developed quickly, yet under circumstances of uncertainty. Time pressure and social pressure in decision-making often go hand in hand with a lack of a solid evidence base and experience that can be drawn on. Another key difficulty is that crisis management measures need to be implemented at the same time as current affairs continue to be managed. In this statement, the European Group on Ethics in Science and New Technologies (EGE) addresses how ethical values can contribute to strategic crisis management. Values play an important role in how we understand and make sense of crises. They influence how we frame the problems that strategic crisis management is supposed to address and how we choose the instruments to do so. Very often, however, values remain implicit and invisible. Foregrounding the values that are inherent in, and should guide, strategic crisis management is an important task to which this statement seeks to contribute. [excerpt from the Introduction]peer-reviewe

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements