Physics News and Discussions

weatheriscool
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Theoretical model offers a new perspective on black hole formation and evolution
https://phys.org/news/2022-04-theoretic ... ation.html
by Ingrid Fadelli , Phys.org

Black holes are regions in space characterized by gravitational fields so intense that no matter or radiation can escape from them. They are solutions to Einstein's field equations, with a point of unphysical infinite density at their center.

Based on the classical theory of general relativity, all the matter that went into forming a black hole ultimately ends up at its center. This specific prediction is known as the "singularity problem."

In one of his seminal works, Stephen Hawking showed that black holes radiate energy and that they slowly disappear. However, his work suggests that the radiation emitted by black holes does not contain all the information about the matter that went into its formation. In astrophysics, this is referred to as the "information loss problem."
weatheriscool
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Large Hadron Collider restarts after three-year break
https://phys.org/news/2022-04-large-had ... -year.html
by Daniel Lawler and Juliette Collen
The Large Hadron Collider has been closed since December 2018 for maintenance and upgrades.

The Large Hadron Collider restarted Friday after a three-year break for upgrades that will allow it to smash protons together at even greater speeds, in the hope of making new ground-breaking discoveries.

It will further study the Higgs boson, the existence of which it proved in 2012, and put the Standard Model of particle physics to the test after recent anomalies sparked theories about a mysterious fifth force of nature.

"Two beams of protons circulated in opposite directions around the Large Hadron Collider's 27-kilometer (17-mile) ring" just after noon on Friday, Europe's physics lab CERN said in a statement.

Buried more than 100 meters (330 feet) beneath the border of Switzerland and France, the collider has been closed since December 2018 for maintenance and upgrades, the second longest shutdown in its 14-year history.

To start with, the collider is taking it easy.
weatheriscool
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Time travel could be possible, but only with parallel timelines
https://phys.org/news/2022-04-parallel-timelines.html
by Barak Shoshany, The Conversation

Have you ever made a mistake that you wish you could undo? Correcting past mistakes is one of the reasons we find the concept of time travel so fascinating. As often portrayed in science fiction, with a time machine, nothing is permanent anymore—you can always go back and change it. But is time travel really possible in our universe, or is it just science fiction?

Our modern understanding of time and causality comes from general relativity. Theoretical physicist Albert Einstein's theory combines space and time into a single entity—"spacetime"—and provides a remarkably intricate explanation of how they both work, at a level unmatched by any other established theory. This theory has existed for more than 100 years, and has been experimentally verified to extremely high precision, so physicists are fairly certain it provides an accurate description of the causal structure of our universe.

For decades, physicists have been trying to use general relativity to figure out if time travel is possible. It turns out that you can write down equations that describe time travel and are fully compatible and consistent with relativity. But physics is not mathematics, and equations are meaningless if they do not correspond to anything in reality.
weatheriscool
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New and surprising duality found in theoretical particle physics
https://phys.org/news/2022-04-duality-t ... ysics.html
by Niels Bohr Institute
A new and surprising duality has been discovered in theoretical particle physics. The duality exists between two types of scattering processes that can occur in the proton collisions made in the Large Hadron Collider at CERN in Switzerland and France. The fact that this connection can, surprisingly, be made points to the fact that there is something in the intricate details of the standard model of particle physics that is not fully understood. The standard model is the model of the world on sub-atomic scale that explains all particles and their interactions, so when surprises appear, there is cause for attention. The scientific article is now published in Physical Review Letters.

Duality in physics

The concept of duality occurs in different areas of physics. The most well known duality is probably the particle-wave duality in quantum mechanics. The famous double-slit experiment shows that light behaves like a wave, while Albert Einstein received his Nobel prize for showing that light behaves like a particle.

The strange thing is that light is actually both and neither of the two at the same time. There are simply two ways we can look at this entity, light, and each comes with a mathematical description. Both with a completely different intuitive idea, but still describe the same thing.
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Yuli Ban
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And remember my friend, future events such as these will affect you in the future
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Yuli Ban
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weatheriscool wrote: Mon Apr 25, 2022 3:55 pm Time travel could be possible, but only with parallel timelines
https://phys.org/news/2022-04-parallel-timelines.html
by Barak Shoshany, The Conversation

Have you ever made a mistake that you wish you could undo? Correcting past mistakes is one of the reasons we find the concept of time travel so fascinating. As often portrayed in science fiction, with a time machine, nothing is permanent anymore—you can always go back and change it. But is time travel really possible in our universe, or is it just science fiction?

Our modern understanding of time and causality comes from general relativity. Theoretical physicist Albert Einstein's theory combines space and time into a single entity—"spacetime"—and provides a remarkably intricate explanation of how they both work, at a level unmatched by any other established theory. This theory has existed for more than 100 years, and has been experimentally verified to extremely high precision, so physicists are fairly certain it provides an accurate description of the causal structure of our universe.

For decades, physicists have been trying to use general relativity to figure out if time travel is possible. It turns out that you can write down equations that describe time travel and are fully compatible and consistent with relativity. But physics is not mathematics, and equations are meaningless if they do not correspond to anything in reality.
I mean, that sounds like a better deal to me. You basically have an infinite number of possibilities
And remember my friend, future events such as these will affect you in the future
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raklian
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To know is essentially the same as not knowing. The only thing that occurs is the rearrangement of atoms in your brain.
weatheriscool
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Single photon emitter takes a step closer to quantum tech
https://phys.org/news/2022-05-photon-em ... -tech.html
by Raphaël Butté, Nik Papageorgiou, Ecole Polytechnique Federale de Lausanne
To get closer to quantum technology we need to develop non-classical light sources that can emit a single photon at a time and do so on demand. Scientists at EPFL have now designed one of these "single photon emitters" that can work at room temperature and is based on quantum dots grown on cost-effective silicon substrates.

Developing non-classical light sources that can emit, on-demand, exactly one photon at a time is one of the main requirements of quantum technologies. But although the first demonstration of such a "single photon emitter," or SPE, dates back to the 1970s, their low reliability and efficiency has been stood in the way of any meaningfully practical use.

Conventional light sources like incandescent light bulbs or LEDs emit bunches of photons at a time. In other words, their probability to emit a single photon at a time is very low. Laser sources can emit streams of single photons, but not on-demand, which means that, sometimes, there will be no photons whatsoever emitted when we want them to.
weatheriscool
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Bilayer graphene inspires two-universe cosmological model

by Bailey Bedford, Joint Quantum Institute
https://phys.org/news/2022-05-bilayer-g ... gical.html
Physicists sometimes come up with crazy stories that sound like science fiction. Some turn out to be true, like how the curvature of space and time described by Einstein was eventually borne out by astronomical measurements. Others linger on as mere possibilities or mathematical curiosities.

In a new paper in Physical Review Research, JQI Fellow Victor Galitski and JQI graduate student Alireza Parhizkar have explored the imaginative possibility that our reality is only one half of a pair of interacting worlds. Their mathematical model may provide a new perspective for looking at fundamental features of reality—including why our universe expands the way it does and how that relates to the most miniscule lengths allowed in quantum mechanics. These topics are crucial to understanding our universe and are part of one of the great mysteries of modern physics.

The pair of scientists stumbled upon this new perspective when they were looking into research on sheets of graphene—single atomic layers of carbon in a repeating hexagonal pattern. They realized that experiments on the electrical properties of stacked sheets of graphene produced results that looked like little universes and that the underlying phenomenon might generalize to other areas of physics. In stacks of graphene, new electrical behaviors arise from interactions between the individual sheets, so maybe unique physics could similarly emerge from interacting layers elsewhere—perhaps in cosmological theories about the entire universe.
weatheriscool
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The standard model of particle physics may be broken, expert says
https://phys.org/news/2022-05-standard- ... xpert.html
by Roger Jones, The Conversation
As a physicist working at the Large Hadron Collider (LHC) at Cern, one of the most frequent questions I am asked is "When are you going to find something?" Resisting the temptation to sarcastically reply "Aside from the Higgs boson, which won the Nobel Prize, and a whole slew of new composite particles?" I realize that the reason the question is posed so often is down to how we have portrayed progress in particle physics to the wider world.

We often talk about progress in terms of discovering new particles, and it often is. Studying a new, very heavy particle helps us view underlying physical processes—often without annoying background noise. That makes it easy to explain the value of the discovery to the public and politicians.

Recently, however, a series of precise measurements of already known, bog-standard particles and processes have threatened to shake up physics. And with the LHC getting ready to run at higher energy and intensity than ever before, it is time to start discussing the implications widely.

In truth, particle physics has always proceeded in two ways, of which new particles is one. The other is by making very precise measurements that test the predictions of theories and look for deviations from what is expected.

The early evidence for Einstein's theory of general relativity, for example, came from discovering small deviations in the apparent positions of stars and from the motion of Mercury in its orbit.
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