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Category: particle physics – Page 464

The periodic table contains a wide array of elements, numbered from one (hydrogen) to 118 (oganesson), with each number representing the number of protons stored within an atom’s nucleus. Scientists are constantly working to create new elements by cramming more and more protons into nuclei, expanding the periodic table. The effort sparks curiosity and questions: Can the table be enlarged in the opposite direction? Is it possible to make an element zero? Does it already exist?

“Element zero” has been a matter of conjecture for nearly a century, and no scientist searched more ardently for it than German chemist Andreas von Antropoff. It was Antropoff who placed the theoretical element atop a periodic table of his own devising, and it was also he who thought up a prescient name for it: neutronium.

You don’t widely hear Antropoff’’s name today, as his Nazi leanings earned the scientist international disgrace. You do, however, hear about neutronium. Today, the term commonly refers to a gaseous substance composed almost purely of neutrons, found within the tiniest, densest stars known to exist: neutron stars.

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Yay face_with_colon_three

Austrian and Chinese scientists have succeeded in teleporting three-dimensional quantum states for the first time. High-dimensional teleportation could play an important role in future quantum computers.

Researchers from the Austrian Academy of Sciences and the University of Vienna have experimentally demonstrated what was previously only a theoretical possibility. Together with quantum physicists from the University of Science and Technology of China, they have succeeded in teleporting complex high-dimensional quantum states. The research teams report this international first in the journal Physical Review Letters.

In their study, the researchers teleported the of one photon (light particle) to another distant one. Previously, only two-level states (“qubits”) had been transmitted, i.e., information with values “0” or “1”. However, the scientists succeeded in teleporting a three-level state, a so-called “qutrit”. In , unlike in classical computer science, “0” and “1” are not an ‘either/or’ – both simultaneously, or anything in between, is also possible. The Austrian-Chinese team has now demonstrated this in practice with a third possibility “2”.

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One of the all-time great mysteries in physics is why our universe contains more matter than antimatter, which is the equivalent of matter but with the opposite charge. To tackle this question, our international team of researchers have managed to create a plasma of equal amounts of matter and antimatter – a condition we think made up the early universe.

Matter as we know it appears in four different states: solid, liquid, gas, and plasma, which is a really hot gas where the atoms have been stripped of their electrons. However, there is also a fifth, exotic state: a matter-antimatter plasma, in which there is complete symmetry between negative particles (electrons) and positive particles (positrons).

This peculiar state of matter is believed to be present in the atmosphere of extreme astrophysical objects, such as black holes and pulsars. It is also thought to have been the fundamental constituent of the universe in its infancy, in particular during the Leptonic era, starting approximately one second after the Big Bang.

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Circa 2011

Considering the amount of energy packed in the nucleus of a single uranium atom, or the energy that has been continuously radiating from the sun for billions of years, or the fact that there are 1080 particles in the observable universe, it seems that the total energy in the universe must be an inconceivably vast quantity. But it’s not; it’s probably zero.

Light, matter and antimatter are what physicists call “positive energy.” And yes, there’s a lot of it (though no one is sure quite how much). Most physicists think, however, that there is an equal amount of “negative energy” stored in the gravitational attraction that exists between all the positive-energy particles. The positive exactly balances the negative, so, ultimately, there is no energy in the universe at all.

Negative energy?

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fusionsunLast year, Pentagon mad science arm DARPA was working on one of its wildest projects yet: a microchip-sized nuclear reactor. The program is now officially done, the agency says. But these sorts of far-out projects have a habit of being reemerging under new managers and new names.

The project, known as the “Chip-Scale High Energy Atomic Beams” program, is an effort aimed at working on the core technologies behind a tiny particle accelerator, capable of firing subatomic particles at incredible speeds. It’s part of a larger DARPA plan to reduce all sorts of devices to microchip-scale – including cryogenic coolers, video cameras and multi-purpose sensors. All of the projects are ambitious (this is DARPA, after all). But this had to be the most ambitious of the lot. Here’s how DARPA’s plans for fiscal year 2009 described it:

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How do you weigh a ghost? If you’re a cosmologist, you could use… the Universe. Combine vast cosmological data with info from particle accelerators, and, it turns out, you have a pretty good scale for measuring the mass of a neutrino — also known as the ‘ghost particle’.

This is how a team of scientists, for the first time, have set an upper limit on the mass of the lightest of the three different types of neutrino.

Neutrinos are peculiar little things. They are among the most abundant subatomic particles in the Universe, similar to electrons, but without a charge and almost massless. This means they interact very rarely with normal matter; in fact, billions are passing through your body right now.

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Physicists have found “electron pairing,” a hallmark feature of superconductivity, at temperatures and energies well above the critical threshold where superconductivity happens.

Rice University’s Doug Natelson, co-corresponding author of a paper about the work in this week’s Nature, said the discovery of Cooper pairs of electrons “a bit above the critical temperature won’t be ‘crazy surprising’ to some people. The thing that’s more weird is that it looks like there are two different energy scales. There’s a higher energy scale where the pairs form, and there’s a lower energy scale where they all decide to join hands and act collectively and coherently, the behavior that actually brings about superconductivity.”

Electrical resistance is so common in the modern world that most of us take it for granted that computers, smartphones and warm up during use. That heating happens because electricity doesn’t flow freely through the metal wires and silicon chips inside the devices. Instead, flowing electrons occasionally bump into atoms or one another, and each collision produces a tiny bit of heat.

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Vast interstellar events where clouds of charged matter hurtle into each other and spew out high-energy particles have now been reproduced in the lab with high fidelity. The work, by MIT researchers and an international team of colleagues, should help resolve longstanding disputes over exactly what takes place in these gigantic shocks.

Many of the largest-scale events, such as the expanding bubble of matter hurtling outward from a supernova, involve a phenomenon called collisionless . In these interactions, the clouds of gas or plasma are so rarefied that most of the particles involved actually miss each other, but they nevertheless interact electromagnetically or in other ways to produces visible shock waves and filaments. These high-energy events have so far been difficult to reproduce under laboratory conditions that mirror those in an astrophysical setting, leading to disagreements among physicists as to the mechanisms at work in these astrophysical phenomena.

Now, the researchers have succeeded in reproducing critical conditions of these collisionless shocks in the laboratory, allowing for detailed study of the processes taking place within these giant cosmic smashups. The new findings are described in the journal Physical Review Letters, in a paper by MIT Plasma Science and Fusion Center Senior Research Scientist Chikang Li, five others at MIT, and 14 others around the world.

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Researchers have developed artificial ‘chameleon skin’ that changes color when exposed to light and could be used in applications such as active camouflage and large-scale dynamic displays.

The material, developed by researchers from the University of Cambridge, is made of tiny particles of gold coated in a polymer shell, and then squeezed into microdroplets of water in oil. When exposed to heat or , the particles stick together, changing the color of the material. The results are reported in the journal Advanced Optical Materials.

In nature, animals such as chameleons and cuttlefish are able to change color thanks to chromatophores: skin cells with contractile fibers that move pigments around. The pigments are spread out to show their color, or squeezed together to make the cell clear.

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