For Star Wars fans, stripes of stars observed from the cockpit of the Millennium Falcon as they jump into hyperspace are a canonical image. But what would a pilot actually see if he could accelerate for a moment through the vacuum of space? According to a forecast known as the Unruh effect, she is more likely to see a warm glow.
Since the 1970s, when it was first proposed, the Unruh effect has been avoided, mainly because the probability of seeing the effect is infinitesimal, requiring either huge accelerations or a huge amount of observation time. But researchers at the Massachusetts Institute of Technology and the University of Waterloo believe they have found a way to significantly increase the likelihood of seeing the Unruh effect, which they describe in a study that appears today in the Physical Review Letters.
Instead of observing the effect spontaneously, as others have tried in the past, the team offers to stimulate the phenomenon in a very specific way, which enhances the effect of Unruh, while suppressing other competitive effects. Researchers liken their idea to throwing an invisible cloak over other conventional phenomena, which should then reveal the much less obvious effect of Unruh.
If it can be implemented in a practical experiment, this new stimulated approach, with an added layer of invisibility (or “acceleration-induced transparency” as described in the document), can significantly increase the likelihood of observing the Unruh effect. Instead of waiting longer than the age of the accelerated particle universe to produce a warm glow, as predicted by the Unruh effect, the team’s approach will reduce this waiting time to a few hours.
“At least now we know we have a chance to see this effect in our lives,” said study co-author Vivishek Sudhir, an assistant professor of mechanical engineering at the Massachusetts Institute of Technology who is designing an experiment to capture the effect based on group theory. “This is a difficult experiment and there is no guarantee that we will be able to do it, but this idea is our closest hope.”
The study also co-authored Barbara Shoda and Achim Kempf of the University of Waterloo.
Close relationship
The Unru effect is also known as the Fuling-Davis-Unru effect, after the three physicists who originally proposed it. The prognosis is that a body that is accelerated by a vacuum should actually feel the presence of heat radiation only as an effect of accelerating the body. This effect is related to the quantum interactions between accelerated matter and quantum fluctuations in the vacuum of empty space.
To produce a glow warm enough for detectors to measure, a body like an atom would have to accelerate to the speed of light in less than a millionth of a second. Such an acceleration would be equivalent to a g-force of quadrillion meters per second squared (a fighter pilot typically experiences a g-force of 10 meters per second squared).
“To see this effect in a short period of time, you will have to have some incredible acceleration,” says Sudhir. “If you had some reasonable acceleration instead, you’ll have to wait a huge amount of time – longer than the age of the universe – to see a measurable effect.
Then what would be the point? On the one hand, he says, observing the Unruh effect would be a validation of the fundamental quantum interactions between matter and light. On the other hand, the discovery may be a mirror of the Hawking effect – a proposal by physicist Stephen Hawking, which predicts similar thermal radiance or “Hawking radiation” from the interactions of light and matter in an extreme gravitational field such as Black Hole.
“There is a close connection between the Hawking effect and the Unru effect – they are exactly the complementary effect of each other,” said Sudhir, who added that if one had to observe the Unru effect, one would observe a mechanism that is common. for both effects. “
Transparent trajectory
The Unruh effect is thought to occur spontaneously in a vacuum. According to quantum field theory, a vacuum is not just an empty space, but rather a field of restless quantum fluctuations, with each frequency band half the size of a photon. Unru predicts that a body accelerating through a vacuum must amplify these fluctuations in a way that produces a warm, thermal glow of particles.
In their study, the researchers introduced a new approach to increase the likelihood of the Unruh effect by adding light to the whole scenario – an approach known as stimulation.
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“When you add photons to a field, you add ‘n’ times more than these fluctuations than that half photon in the vacuum,” Sudhir explains. “So if you accelerate through this new state of the field, you would expect to see effects that are also scaled n times larger than you would see from a vacuum alone.”
However, in addition to the Unruh quantum effect, additional photons would also amplify other effects in the vacuum – a major drawback that prevents other Unruh effect hunters from taking the stimulation approach.
However, Shoda, Sudhir and Kempf found a way around it through “acceleration-driven transparency”, a concept they are introducing in the article. They have shown theoretically that if a body as an atom can be made to accelerate by a very specific trajectory through a field of photons, the atom will interact with the field in such a way that photons of a certain frequency will essentially appear invisible to the atom.
“When we stimulate the Unruh effect, at the same time we also stimulate conventional or resonant effects, but we show that by designing the particle trajectory we can essentially eliminate these effects,” says Shoda.
By making all other effects transparent, researchers could be more likely to measure photons or heat radiation coming from the Unruh effect alone, as physicists have predicted.
Researchers already have some ideas on how to design an experiment based on their hypothesis. They plan to build a laboratory-sized particle accelerator capable of accelerating an electron to the speed of light, which they can then stimulate with a microwave-wavelength laser beam. They are looking for ways to design the path of electrons to suppress classical effects, while enhancing the elusive effect of Unruh.
“We now have this mechanism that seems to be statistically amplifying this effect through stimulation,” Sudhir said. “Given the 40-year history of this problem, we have now, in theory, removed the biggest bottleneck.”
This study was supported in part by the National Research and Engineering Council of Canada, the Australian Research Council and the Google Research Award.
Republished with permission from MIT News. Read the original article.
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