RESUMO
The understanding of nonequilibrium dynamics in many-body quantum systems is a fundamental issue in statistical physics. Experiments that probe universal properties of these systems can address such foundational questions. In this study, we report the measurement of universal dynamics triggered by a quench from the superfluid to normal phase across the Berezinskii-Kosterlitz-Thouless transition in a two-dimensional (2D) Bose gas. We reduced the density by splitting the 2D gas in two, realizing a quench across the critical point. The subsequent relaxation dynamics were probed with matter-wave interferometry to measure the local phase fluctuations. We show that the time evolution of both the phase correlation function and vortex density obeys universal scaling laws. This conclusion is supported by classical-field simulations and interpreted by means of real-time renormalization group theory.
RESUMO
During the United Kingdom's Covid-19 vaccination campaign, general practitioners (GPs) have held responsibility for vaccinating housebound patients. This presented them with a large, complex and unfamiliar logistical challenge, namely determining the most time-efficient route to visit multiple patients at their home address. In response to a lack of existing solutions tailored specifically to vaccination, and in light of overwhelming demand, Vaximap ( https://www.vaximap.org ) was created in January 2021 to automate the process of route planning. It is free of charge for all users and has been used to-date to plan vaccinations for over 470,000 patients. This article analyses usage data to estimate the time savings (3 work years) and financial savings (£110,000) the service has yielded for GP surgeries, thus demonstrating that it helped to accelerate the UK's Covid-19 vaccination campaign at critical moments.