Latest news with #UniversityOfLisbon
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44 minutes ago
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Light Squeezed Out of Darkness in Surprising Quantum Simulation
A careful alignment of three powerful lasers could generate a mysterious fourth beam of light that is throttled out of the very darkness itself. What sounds like occult forces at work has been confirmed by a simulation of the kinds of quantum effects we might expect to emerge from a vacuum when ultra-high electromagnetic fields meet. A team of researchers from the University of Oxford in the UK and the University of Lisbon in Portugal used a semi-classical equation solver to simulate quantum phenomena in real time and in three dimensions, testing predictions on what ought to occur when incredibly intense laser pulses combine in empty space. "This is not just an academic curiosity – it is a major step toward experimental confirmation of quantum effects that until now have been mostly theoretical," says Oxford physicist Peter Norreys. Laser technology has come a long way since its invention a little over half a century ago. Focussing petawatts of power in mere instants of time, they're theorized to be capable of literally shaking matter out of the very fabric of reality itself. What we think of as empty space is – on a quantum level – an ocean of possibility. Fields representing all kinds of physical interactions hum with the promise of particles we'd recognize as the foundations of light and the building blocks of matter itself. These virtual particles essentially pop into and out of existence in fractions of a second. All it takes for them to manifest longer-term is the right kind of physical persuasion that discourages them from canceling one another out; the kind of persuasion a series of strong electromagnetic fields might provide when arranged in a suitable fashion, for example. To determine whether predictions on the power of lasers could indeed generate something from nothing, Norreys and his team ran computational models based on the mathematics underpinning electromagnetic fields in a vacuum. Plugging numbers into their solver revealed that blending three suitably strong laser beams and their electromagnetic fields can generate a level of polarization that forces virtual photons to part before they blur out of existence. Known as four-wave mixing, the scattered photons would appear as a fourth beam of light. This kind of photon-photon scattering has long been predicted as possible, yet attempts to observe it in reality have so far proven ineffective. "By applying our model to a three-beam scattering experiment, we were able to capture the full range of quantum signatures, along with detailed insights into the interaction region and key time scales," says the study's lead author, physicist Zixin Zhang at Oxford. While the findings are all numerical for now, they do provide a more physically realistic description of what to expect than previous models. We may not need to wait all that long for the results to be put to the ultimate test either. The Extreme Light Infrastructure project in Romania is currently home to the world's most advanced high-power laser infrastructure, already achieving averages of around 10 petawatts in ultrashort bursts of light. Meanwhile, the EP-OPAL project at the University of Rochester in the US has two 25-petawatt beams in the works, with photon-photon scattering experiments already being planned. The Shanghai High repetition rate X-ray Free Electron Laser and Extreme light facility in China also hopes to smash records this year, aiming for 100 petawatts using its free-electron technology. Using nothing but photons to generate the necessary electromagnetic fields, it's hoped the light being scattered out of the darkness won't be hidden in a fog of other particles, finally proving once and for all that it is possible in physics to squeeze something out of nothing. This research was published in Communications Physics. Physicists Actually Made The 'World's Smallest Violin' For a Serious Reason Spiral Magnetism Seen in Synthetic Crystal For The First Time We've Been Misreading a Major Law of Physics For Nearly 300 Years
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a day ago
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Tectonic plates can spread subduction like a contagion — jumping from one oceanic plate to another
When you buy through links on our articles, Future and its syndication partners may earn a commission. Subduction zones, where one tectonic plate dives underneath another, drive the world's most devastating earthquakes and tsunamis. How do these danger zones come to be? A study in Geology presents evidence that subduction can spread like a contagion, jumping from one oceanic plate to another — a hypothesis previously difficult to prove. This result "is not just speculation," says University of Lisbon geologist João Duarte, who was not involved in the research. "This study builds an argument based on the geological record." Because subduction drags crust deep into the earth, its beginnings are hard to examine. The new study provides a rare ancient example of potential subduction "infection." Its authors say they've discovered evidence that neighboring collisions triggered East Asia's "Ring of Fire," a colossal subduction system currently fueling earthquakes and volcanoes from Alaska to the southern Indian Ocean. Nearly 300 million years ago China was a scattering of islands separated by the ancient Tethys and Asian oceans. Established subduction zones consumed these oceans, welding the landmasses into a new continent and raising mountains from Turkey to China. By 260 million years ago this subduction seems to have spread and begun pulling down the neighboring Pacific plate. "The dying act of those closing oceans may have been to infect the Pacific plate and start it subducting westward under the Asian continent," says study lead author Mark Allen, a geologist at Durham University in England. "In one form or another, it's been diving down ever since." The smoking gun in this case is the "Dupal anomaly," identified by a geochemical fingerprint from the ancient Tethys Ocean and what is now the Indian Ocean. When the study authors unexpectedly found this signature in volcanic rocks from the western Pacific, they surmised that material from the Tethys had spread eastward across a plate boundary from one subduction zone to another — triggering the neighboring plate's descent. "It's like seeing someone's fingerprint at a crime scene," Allen says. RELATED STORIES —Africa is being torn apart by a 'superplume' of hot rock from deep within Earth, study suggests —Gigantic 'mud waves' buried deep beneath the ocean floor reveal dramatic formation of Atlantic when Africa and South America finally split —Yosemite's ultra-deep canyon may have been carved in part by a ghost volcano and river, provocative research suggests But the mechanism of spread remains mysterious. The researchers suspect that transform faults — boundaries where plates slide past one another, like the San Andreas Fault — may act as weak spots where slight changes in collision angle or speed can destabilize dense oceanic crust, causing it to sink. Duarte compares the scenario to aluminum foil in water. "The foil floats," he says, "but the slightest tap will cause it to sink." If subduction spreads this way, could the Atlantic Ocean's relatively quiet plate margins be next? The massive 1755 Lisbon earthquake hints at early subduction invasion there. Duarte suggests parts of Iberia and the Caribbean are undergoing this process's initial stages: "In another 100 million years a new Atlantic 'Ring of Fire' may form — just as it once did in the Pacific." This article was first published at Scientific American. © All rights reserved. Follow on TikTok and Instagram, X and Facebook.
