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Category: particle physics – Page 456

The standard model of physics remains incomplete. Could supersymmetry fill the gaps? From whether supersymmetric particles could fix the mass of the Higgs Boson to what this would mean for string theory, the world’s leading thinkers explain all.

John Ellis is a British theoretical physicist who is currently Clerk Maxwell Professor of Theoretical Physics at King’s College London. He was Division Leader for the CERN theory division, a founding member of the LEPC and of the LHCC at CERN and currently chair of the committee to investigate physics opportunities for future proton accelerators.

Catherine Heymans is a Professor of Astrophysics and European Research Council Fellow at the University of Edinburgh. She is also the Director of the German Centre for Cosmological Lensing at the Ruhr-University Bochum, Germany.

Ben Allanach is a member of the Department of Applied Mathematics and Theoretical Physics High Energy Physics research group and The Cambridge SUSY Working Group based at the Cavendish Laboratory.

Continue reading “On Supersymmetry | John Ellis, Catherine Heymans, Ben Allanach, Subir Sakar, Cumrun Vafa” | >

When a single neutrino was detected by a neutrino detector in Antarctica in September 2017, it was the start of something amazing. It was to become the first-ever high-energy neutrino that astronomers could trace back to an origin — a blazar galaxy called TXS 0506+056, 3.8 billion light-years away.

But, in the manner of many great discoveries, that revelation opened up a whole new can of questions, including this: why, of all the galaxies with similar properties, has a neutrino only ever been traced to this one?

Now, astronomers have found a possible answer, pinpointing the source event that produced this neutrino. The relativistic jet blasting out of a supermassive black hole could have acted as a cosmic particle collider, producing a flurry of neutrinos that, due to the shape and wobble of the jet, ended up streaming through Earth.

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As quantum objects are susceptible to their surrounding environment, quantum coherence and quantum states can easily be destroyed due to the impact of external signals, which can include thermal noise and backscattered signals in the measurement circuit. Researchers have thus been trying to develop techniques to enable nonreciprocal signal propagation, which could help to block the undesired effects of backward noise.

In a recent study, members of the dynamic spintronics group at the University of Manitoba in Canada have proposed a new method to produce dissipative coupling in hybrid quantum systems. Their technique, presented in a paper published in Physical Review Letters, enables nonreciprocal signal propagation with a substantial isolation ratio and flexible controllability.

“Our recent work on nonreciprocity in cavity magnonics is grounded in a research area combining cavity spintronics and hybrid quantum systems, which holds promise for constructing new quantum information processing platforms,” Yi-Pu Wang, a postdoctoral researcher at the University of Manitoba who was involved in the study, told Phys.org.

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Dark matter was likely the starting ingredient for brewing up the very first galaxies in the universe. Shortly after the Big Bang, particles of dark matter would have clumped together in gravitational “halos,” pulling surrounding gas into their cores, which over time cooled and condensed into the first galaxies.

Although dark matter is considered the backbone to the structure of the universe, scientists know very little about its nature, as the particles have so far evaded detection.

Now scientists at MIT, Princeton University, and Cambridge University have found that the early universe, and the very first galaxies, would have looked very different depending on the nature of dark matter. For the first time, the team has simulated what early galaxy formation would have looked like if dark matter were “fuzzy,” rather than cold or warm.

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After counting all the normal, luminous matter in the obvious places of the universe – galaxies, clusters of galaxies and the intergalactic medium – about half of it is still missing. So not only is 85 percent of the matter in the universe made up of an unknown, invisible substance dubbed “dark matter”, we can’t even find all the small amount of normal matter that should be there.

This is known as the “missing baryons” problem. Baryons are particles that emit or absorb light, like protons, neutrons or electrons, which make up the matter we see around us. The baryons unaccounted for are thought to be hidden in filamentary structures permeating the entire universe, also known as “the cosmic web”.

But this structure is elusive and so far we have only seen glimpses of it. Now a new study, published in Science, offers a better view that will enable us to help map what it looks like.

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Energy is a quantity that must always be positive—at least that’s what our intuition tells us. If every single particle is removed from a certain volume until there is nothing left that could possibly carry energy, then a limit has been reached. Or has it? Is it still possible to extract energy even from empty space?

Quantum physics has shown time and again that it contradicts our intuition, which is also true in this case. Under certain conditions, negative energies are allowed, at least in a certain range of space and time. An international research team at the TU Vienna, the Université libre de Bruxelles (Belgium) and the IIT Kanpur (India) have now investigated the extent to which negative is possible. It turns out that no matter which quantum theories are considered, no matter what symmetries are assumed to hold in the universe, there are always certain limits to “borrowing” energy. Locally, the energy can be less than zero, but like money borrowed from a bank, this energy must be “paid back” in the end.

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Investigating the heaviest elements known is rewriting our knowledge of chemistry and may even mean the end of the periodic table itself, writes Kit Chapman.

In 2018, Peter Schwerdtfeger published a paper that turned chemistry on its head. According to calculations he and his colleagues performed, oganesson – element 118, the heaviest known – was not a noble gas as you would expect from its position in the periodic table, but a highly reactive solid. Even stranger, it didn’t seem to have electron shells.1

‘Well, that statement is oversimplified,’ says Schwerdtfeger, a theoretical chemist at Massey University in New Zealand. ‘You can still build up the electron densities from orbitals describing individual shells. What happens is that for oganesson the shell structure is barely visible, approaching an electron gas.’

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The news: A gel developed by Stanford researchers could be sprayed on forests and vegetation to make them fire-resistant, helping to stop wildfires from spreading. It’s made from cellulose polymers (extracted from plants) and particles of silica, which are chemically identical to sand, mixed with a flame-retardant fluid.

How to use it: Fire-fighting sprays are currently used on wildfires only in emergencies: this new approach would deploy them protectively before any fires can break out. In a paper in Proceedings of the National Academy of Sciences, the researchers say the gel is nontoxic and biodegradable.

Rain-resistant: The team tested the gel on plants in the laboratory and then on patches of grass by a road in California, supervised by local firefighters. They found it can withstand wind and up to half an inch of rain, so iy only needs to be applied once per fire season (if it rains more than that, the risk of wildfires plummets anyway).

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