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Category: particle physics

Credit where credit is due: Evolution has invented a galaxy of clever adaptations, from fish that swim up sea cucumber butts and eat their gonads, to parasites that mind-control their hosts in wildly complex ways. But it’s never dreamed up ion propulsion, a fantastical new way to power robots by accelerating ions instead of burning fuel or spinning rotors. The technology is in very early development, but it could lead to machines that fly like nothing that’s come before them.

You may have heard of ion propulsion in the context of spacecraft, but this application is a bit different. Most solar-powered ion spacecraft bombard xenon atoms with electrons, producing positively charged xenon ions that then rush toward a negatively charged grid, which accelerates the ions into space. The resulting thrust is piddling compared to traditional engines, and that’s OK—the spacecraft is floating through the vacuum of space, so the shower of ions accelerate the aircraft bit by bit.

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Every type of atom in the universe has a unique fingerprint: It only absorbs or emits light at the particular energies that match the allowed orbits of its electrons. That fingerprint enables scientists to identify an atom wherever it is found. A hydrogen atom in outer space absorbs light at the same energies as one on Earth.

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The cold fusion dream lives on: NASA is developing cheap, clean, low-energy nuclear reaction (LENR) technology that could eventually see cars, planes, and homes powered by small, safe nuclear reactors.

When we think of nuclear power, there are usually just two options: fission and fusion. Fission, which creates huge amounts of heat by splitting larger atoms into smaller atoms, is what currently powers every nuclear reactor on Earth. Fusion is the opposite, creating vast amounts of energy by fusing atoms of hydrogen together, but we’re still many years away from large-scale, commercial fusion reactors. (See: 500MW from half a gram of hydrogen: The hunt for fusion power heats up.)

A nickel lattice soaking up hydrogen ions in a LENR reactor

LENR is absolutely nothing like either fission or fusion. Where fission and fusion are underpinned by strong nuclear force, LENR harnesses power from weak nuclear force — but capturing this energy is difficult. So far, NASA’s best effort involves a nickel lattice and hydrogen ions. The hydrogen ions are sucked into the nickel lattice, and then the lattice is oscillated at a very high frequency (between 5 and 30 terahertz). This oscillation excites the nickel’s electrons, which are forced into the hydrogen ions (protons), forming slow-moving neutrons. The nickel immediately absorbs these neutrons, making it unstable. To regain its stability, the nickel strips a neutron of its electron so that it becomes a proton — a reaction that turns the nickel into copper and creates a lot of energy in the process.

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Oxidation numbers have so far eluded any rigorous quantum mechanical definition. A new SISSA study, published in Nature Physics, provides such a definition based on the theory of topological quantum numbers, which was honored with the 2016 Nobel Prize in Physics, awarded to Thouless, Haldane and Kosterlitz. This result, combined with recent advances in the theory of transport achieved at SISSA, paves the way to an accurate, yet tractable, numerical simulation of a broad class of materials that are important in energy-related technologies and planetary sciences.

Every undergraduate student in the natural sciences learns how to associate an integer oxidation number to a chemical species participating in a reaction. Unfortunately, the very concept of oxidation state has thus far eluded a rigorous quantum mechanical definition, so that no method was known until now to compute oxidation numbers from the fundamental laws of nature, let alone demonstrate that their use in the simulation of charge transport does not spoil the quality of numerical simulations. At the same time, the evaluation of electric currents in ionic conductors, which is required to model their transport properties, is presently based on a cumbersome quantum-mechanical approach that severely limits the feasibility of large-scale computer simulations. Scientists have lately noticed that a simplified model where each atom carries a charge equal to its oxidation number may give results in surprising good agreement with rigorous but much more expensive approaches.

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Researchers at the University of Southampton and the Korea Institute for Advanced Study have recently showed that supersymmetry is anomalous in N=1 superconformal quantum field theories (SCFTs) with an anomalous R symmetry. The anomaly described in their paper, published in Physical Review Letters, was previously observed in holographic SCFTs at strong coupling, yet their work confirms that it is already present in the simplest free STFCs.

“Supersymmetry is a symmetry that relates particles with integer and half-integer spin, and has played a central role in many advances in since its discovery,” Kostas Skenderis, one of the researchers who carried out the study, told Phys.org. “It has been used as a means to understand the behavior of strongly interacting where our usual theoretical tools () are not applicable, as well as in some of the main candidates for beyond the Standard Model physics.”

Supersymmetry underlies the mathematical consistency of string theory, which is the most complete theory of gravity proposed so far. A quantum anomaly, such as that observed by the researchers, is essentially the failure of a symmetry to be preserved at a quantum level. These anomalies typically come in two types: “bad” ones, which render string theory mathematically inconsistent and “healthy” ones, which capture important quantum properties of the theory.

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It actually makes more sense that all the foundational physics laws do not exist but somehow they do. That is why I still believe there is some governing force that controls the parameters possibly. It makes more sense that our universe somehow was not created than it all somehow just magically sustained itself. That is why I think aliens created the universe as a containment possibly or that the laws of physics somehow are not completely know of how they all work together. Some talk about super symmetry but still seems some sorta things are still not know and we may never know until the theory of everything can be created.

Our best theories predict that all the matter in the universe should have been destroyed as soon as it existed. So how comes there’s something, not nothing?

By Daniel Cossins

Mystery: Why does anything exist at all?

THERE is plenty to recommend the standard model, our best description of particles and their interactions. But it has the odd awkward lapse. “It is a somewhat embarrassing fact that it fails to explain our existence,” says Werner Rodejohann at the Max Planck Institute for Nuclear Physics in Germany.

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