Physics Today Daily Edition
Guardian: At a meeting in Ottawa, Canada, this week, Barack Obama, Justin Trudeau, and Enrique Peña Nieto will commit to a plan to have the US, Canada, and Mexico produce half their electricity from hydropower, wind, solar, and nuclear plants by 2025. That represents a large increase from the current collective clean power levels of about 37%. The agreement will also include plans for carbon capture and storage and energy efficiency measures. Because the US accounts for 75% of the three countries' energy production and only one third of its production is from clean energy, it will have the most work to do to reach the stated goal. A Supreme Court ruling earlier this year halted Obama's attempt to reduce coal plant emissions to meet emissions targets set at the 2015 Paris climate conference. Although Mexico currently produces less than 20% of its electricity from clean sources, Canada gets 81% of its power from renewables.
Washington Post: Both David Cameron, who announced that he will step down as prime minister in October, and leading proponents of the UK's departure from the European Union have called for a delay in beginning the country's formal exit. Cameron has said that he would leave the invocation of Article 50 of the Lisbon Treaty to his successor and that the exit has to be officially approved by Parliament. However, some officials, such as France's finance minister Michel Sapin, have suggested that the UK should begin the process as soon as possible. Angela Merkel says she is against conducting informal negotiations that might give the UK more time, but a foreign policy official indicated that the German chancellor might be more accommodating if the UK seriously reconsiders its exit decision.
Nature: Einstein's general relativity has been used to model the expansion of the early universe, but only in a simplified form. The complexity of the equations requires the assumption that matter was uniformly distributed in the early universe, which likely does not match reality. Even after the development of supercomputers, calculations continued the simplification for models that extended beyond a small region. Now two groups have independently created full-universe simulations that include a non-uniform distribution of matter. One group—led by Eloisa Bentivegna of the University of Catania, Italy, and Marco Bruni of the University of Portsmouth, UK—developed a model to study the formation of large, superdense structures. The model developed by the other group—led by Glenn Starkman of Case Western Reserve University in Cleveland, Ohio—focuses on how the universe expands and how its curvature affects the propagation of light. Both groups' models used numerical-solution techniques that were developed for calculating the warping of spacetime caused by black hole pairs like those that created the recently detected gravitational waves.
New Scientist: On 23 June, NASA announced that it intends to continue using the Hubble Space Telescope through June 2021. Launched in 1990 and last serviced in 2009, Hubble can easily continue working into the 2020s, NASA says. The extension of Hubble means the telescope will still be in use when its successor, the James Webb Space Telescope (JWST), is launched in 2018. Using the two telescopes in tandem will provide a valuable opportunity to study objects with Hubble's visible and UV cameras and JWST's IR cameras.
Nature: Simulations of phenomena involving the strong nuclear force are too hard to perform from first principles on classical computers. Now Esteban Martinez of the University of Innsbruck in Austria and his colleagues have used a quantum computer to complete a proof-of-concept simulation of the conversion of energy into an electron and positron pair. It's the first time a quantum computer has been used to simulate a high-energy physics experiment. The simulation matched the predictions of a simplified form of quantum electrodynamics. The quantum computer contained four qubits in a linear arrangement. Martinez's team now hopes to use a two-dimensional arrangement of qubits and scale up the simulation.