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Category: physics – Page 220

Richard Feynman, one of the most respected physicists of the twentieth century, said “What I cannot create, I do not understand.” Not surprisingly, many physicists and mathematicians have observed fundamental biological processes with the aim of precisely identifying the minimum ingredients that could generate them. One such example are the patterns of nature observed by Alan Turing. The brilliant English mathematician demonstrated in 1952 that it was possible to explain how a completely homogeneous tissue could be used to create a complex embryo, and he did so using one of the simplest, most elegant mathematical models ever written. One of the results of such models is that the symmetry shown by a cell or a tissue can break under a set of conditions.

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Dotty graphene and doping: Whatever it takes for Russia’s record plasmonics to shine.

Physicists from MIPT and Vladimir State University, Russia, have achieved a nearly 90% efficiency converting light energy into surface waves on graphene. They relied on a laser-like energy conversion scheme and collective resonances. The paper came out in Laser & Photonics Reviews.

Manipulating light at the nanoscale is a task crucial for being able to create ultracompact devices for optical energy conversion and storage. To localize light on such a small scale, researchers convert optical radiation into so-called surface plasmon-polaritons. These SPPs are oscillations propagating along the interface between two materials with drastically different refractive indices — specifically, a metal and a dielectric or air. Depending on the materials chosen, the degree of surface wave localization varies. It is the strongest for light localized on a material only one atomic layer thick, because such 2D materials have high refractive indices.

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No one has yet managed to travel through time – at least to our knowledge – but the question of whether or not such a feat would be theoretically possible continues to fascinate scientists.

As movies such as The Terminator, Donnie Darko, Back to the Future and many others show, moving around in time creates a lot of problems for the fundamental rules of the Universe: if you go back in time and stop your parents from meeting, for instance, how can you possibly exist in order to go back in time in the first place?

It’s a monumental head-scratcher known as the ‘grandfather paradox’, but in September last year a physics student Germain Tobar, from the University of Queensland in Australia, said he has worked out how to “square the numbers” to make time travel viable without the paradoxes.

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If our universe is a bubble that inflated inside a larger multiverse, it might bear scars from collisions with nearby bubbles.

What lies beyond all we can see? The question may seem unanswerable. Nevertheless, some cosmologists have a response: Our universe is a swelling bubble. Outside it, more bubble universes exist, all immersed in an eternally expanding and energized sea — the multiverse.

The idea is polarizing. Some physicists embrace the multiverse to explain why our bubble looks so special (only certain bubbles can host life), while others reject the theory for making no testable predictions (since it predicts all conceivable universes). But some researchers expect that they just haven’t been clever enough to work out the precise consequences of the theory yet.

Now, various teams are developing new ways to infer exactly how the multiverse bubbles and what happens when those bubble universes collide.

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Very interesting.

Albert Einstein’s theory of general relativity profoundly changed our thinking about fundamental concepts in physics, such as space and time. But it also left us with some deep mysteries. One was black holes, which were only unequivocally detected over the past few years. Another was “wormholes” – bridges connecting different points in spacetime, in theory providing shortcuts for space travellers.

Wormholes are still in the realm of the imagination. But some scientists think we will soon be able to find them, too. Over the past few months, several new studies have suggested intriguing ways forward.

Black holes and wormholes are special types of solutions to Einstein’s equations, arising when the structure of spacetime is strongly bent by gravity. For example, when matter is extremely dense, the fabric of spacetime can become so curved that not even light can escape. This is a black hole.

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New technology from Stanford scientists finds long-hidden quakes, and possible clues about how earthquakes evolve.

Tiny movements in Earth’s outermost layer may provide a Rosetta Stone for deciphering the physics and warning signs of big quakes. New algorithms that work a little like human vision are now detecting these long-hidden microquakes in the growing mountain of seismic data.

Measures of Earth’s vibrations zigged and zagged across Mostafa Mousavi’s screen one morning in Memphis, Tenn. As part of his PhD studies in geophysics, he sat scanning earthquake signals recorded the night before, verifying that decades-old algorithms had detected true earthquakes rather than tremors generated by ordinary things like crashing waves, passing trucks or stomping football fans.

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Circa 2018 o.o!

We are not living in the first universe. There were other universes, in other eons, before ours, a group of physicists has said. Like ours, these universes were full of black holes. And we can detect traces of those long-dead black holes in the cosmic microwave background (CMB) — the radioactive remnant of our universe’s violent birth.

At least, that’s the somewhat eccentric view of the group of theorists, including the prominent Oxford University mathematical physicist Roger Penrose (also an important Stephen Hawking collaborator). Penrose and his acolytes argue for a modified version of the Big Bang.

In Penrose and similarly-inclined physicists’ history of space and time (which they call conformal cyclic cosmology, or CCC), universes bubble up, expand and die in sequence, with black holes from each leaving traces in the universes that follow. And in a new paper released Aug. 6 in the preprint journal arXiv— apparent evidence for Hawking points in the CMB sky — Penrose, along with State University of New York Maritime College mathematician Daniel An and University of Warsaw theoretical physicist Krzysztof Meissner, argued that those traces are visible in existing data from the CMB.

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