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Category: physics

Ultrafast light-driven electron slide discovered

When an intense laser pulse hits a stationary electron, it performs a trembling motion at the frequency of the light field. However, this motion dies down after the pulse, and the electron comes to rest again at its original location. If, however, the light field changes its strength along the electron’s trajectory, the electron builds up an additional drift motion with each oscillation, which it retains even after the pulse. The spatial light intensity acts like a slope that the electron slides down.

This effect, known for decades, is called ponderomotive acceleration. However, due to the low spatial dependence of intensity even in focused light beams, this light-driven sliding effect can only be clearly observed for long-lasting laser pulses with many oscillations of the field.

In a recent study, researchers have demonstrated pronounced ponderomotive acceleration during just a single light oscillation. The crucial trick was the use of sharp metallic needle tips, which exhibit an extremely strong spatial variation in when illuminated with . The work is published in the journal Nature Physics.

After Over 100 Years, Scientists Are Finally Closing In on the Origins of Cosmic Rays

Researchers are uncovering the origins of cosmic rays, linking them to mysterious cosmic accelerators called PeVatrons New research from astrophysicists at Michigan State University may bring scientists closer to solving a mystery that has puzzled them for more than a century: where do galactic c

Astronomers discover new pulsating ultraluminous X-ray source

Using ESA’s XMM-Newton satellite, European astronomers have observed ultraluminous X-ray sources (ULXs) in the galaxy NGC 4631. As a result, they detected a new pulsating ULX, which received the designation X-8. The research is published November 6 on the arXiv preprint server.

ULXs are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. They are less luminous than , but more consistently luminous than any known stellar process. Although numerous studies of ULXs have been conducted, the basic nature of these sources still remains unknown.

Some persistent ULXs exhibit pulsations and therefore are categorized as ultraluminous X-ray pulsars (ULXPs). Discovering and studying objects of this type could be crucial for advancing our understanding of accretion physics—for instance, mechanisms that enable the sustained X-ray luminosities of ULXs which exceed the Eddington limit.

Statistical mechanics for networks of real neurons

Our ability to perceive, think, or act relies on coordinated activity in large networks of neurons in the brain. This review examines recent progress in connecting ideas from statistical physics, such as maximum entropy methods and the renormalization group, to quantitative experiments that record the electrical activity of thousands of neurons simultaneously. This quantitative bridge between the new data and statistical physics models uncovers new, quantitatively reproducible behaviors and makes clear that abstract theoretical principles in studies of the brain can have the level of predictive power that we expect in other areas of physics.

A Mathematician’s Model Brings Science Fiction’s Wormholes Closer to Reality

Could a tunnel through space and time—long a dream of science fiction—ever exist in theory? According to Arya Dutta, a Ph.D. student in Mathematics at the Katz School, the answer might be yes, at least on paper.

Accepted for publication in the International Journal of Geometric Methods in Modern Physics, Dutta’s study, “Thin-shell Wormhole with a Background Kalb–Ramond Field,” explored a mathematical model of a wormhole—a hypothetical shortcut through spacetime that could, in theory, connect two distant regions of the universe. “A wormhole allows faster-than-light travel or even time travel,” said Dutta. “It hasn’t been observed yet, but theoretical research has advanced a lot.”

‘Impossible’ merger of two massive black holes explained

In 2023, astronomers detected a huge collision. Two unprecedentedly massive black holes had crashed an estimated 7 billion light-years away. The enormous masses and extreme spins of the black holes puzzled astronomers. Black holes like these were not supposed to exist.

Now, astronomers with the Flatiron Institute’s Center for Computational Astrophysics (CCA) and their colleagues have figured out just how these black holes may have formed and collided. The astronomers’ comprehensive simulations—which follow the system from the lives of the parent stars through to their ultimate death—uncovered the missing piece that previous studies had overlooked: magnetic fields.

“No one has considered these systems the way we did; previously, astronomers just took a shortcut and neglected the magnetic fields,” says Ore Gottlieb, astrophysicist at the CCA and lead author of the new study on the work published in The Astrophysical Journal Letters. “But once you consider magnetic fields, you can actually explain the origins of this unique event.”

Harnessing intricate, self-organized plasma patterns to destroy PFAS

Increasing the surface area when plasma and water interact could help scale up a technology that destroys contaminants such as PFAS, detergents and microbial contaminants in drinking water, new research from the University of Michigan shows.

Under certain conditions, when comes in contact with water, it can self-organize, forming intricate patterns resembling stars, wagon wheels or gears that expand the . While the physics of plasma self organization remains elusive, a better understanding can help harness it for more efficient water decontamination.

The U-M research team captured the first images of the water surface below the self-organizing plasma, revealing that the plasma exerts an electrical force on the water that distorts the surface and also generates surface waves.

Cloud droplet microphysics challenges accuracy of current climate models

The way clusters of differently sized water droplet populations are distributed within clouds affects larger-scale cloud properties, such as how light is scattered and how quickly precipitation forms. Studying and simulating cloud droplet microphysical structure is difficult. But recent field observations have provided crucial, centimeter-scale data on cloud droplet size distributions in stratocumulus clouds, giving researchers an opportunity to better match their models to reality.

The simulations of characteristic droplet size distributions that those models are providing are likely too uniform, say Nithin Allwayin and colleagues. This muddled microphysical structure could be leading cloud simulations, and the that use them, astray. Their paper is published in the journal Geophysical Research Letters.

The authors compare the new observed data on cloud microphysical structure with results from large-eddy simulations (LES) of stratocumulus . At convective scales, the model showed intriguing correlations between droplet cluster characteristics and overall cloud physics. For example, regions of the clouds dominated by drizzle tended to have larger drops but not necessarily more total water content, and the updraft regions of clouds tended to have smaller drops and a narrower distribution of droplet size.

New AI framework can uncover space physics equations in raw data

Artificial intelligence (AI) systems, particularly artificial neural networks, have proved to be highly promising tools for uncovering patterns in large amounts of data that would otherwise be difficult to detect. Over the past decade, AI tools have been applied in a wide range of settings and fields.

Among its many possible applications, AI systems could be used to discover physical relationships and symbolic expressions (i.e., ) describing these relationships.

To uncover these formulas, physicists currently need to extensively analyze , thus automating this process could be highly advantageous.

Doomsday Devices & Ontological Weaponry

From nuclear nightmares to reality-breaking weapons, we examine how science and fiction imagine the end of everything. What happens when weapons don’t just destroy worlds but unmake reality itself? Explore the science of apocalypse.

Checkout Scav: https://go.nebula.tv/scav?ref=isaacar… Watch my exclusive video Autonomous Space Industry: https://nebula.tv/videos/isaacarthur–… Nebula using my link for 40% off an annual subscription: https://go.nebula.tv/isaacarthur Visit our Website: http://www.isaacarthur.net Join Nebula: https://go.nebula.tv/isaacarthur Support us on Patreon: / isaacarthur Support us on Subscribestar: https://www.subscribestar.com/isaac-a… Facebook Group: / 1,583,992,725,237,264 Reddit: / isaacarthur Twitter: / isaac_a_arthur on Twitter and RT our future content. SFIA Discord Server: / discord Credits: Doomsday Devices & Ontological Weaponry Written, Produced & Narrated by: Isaac Arthur Editor: Lukas Konecny Select imagery/video supplied by Getty Images Music by Epidemic Sound: http://nebula.tv/epidemic & Stellardrone Chapters 0:00 Intro 1:30 Classical Doomsday Devices 5:57 Cosmic-Scale Doomsday Devices 11:30 Ontological Weaponry – Breaking Reality 12:23 The Erasers of History 16:06 Weapons of Physics Editing 17:55 Mind and Meaning as Targets 20:06 Scavenger Hunt 21:30 Themes and Consequences 22:55 Practical Considerations & Paradoxes 24:07 Doomsday Devices vs. Ontological Weapons 26:48 The Fermi Paradox & Ultimate Destruction.
Watch my exclusive video Autonomous Space Industry: https://nebula.tv/videos/isaacarthur–…
Get Nebula using my link for 40% off an annual subscription: https://go.nebula.tv/isaacarthur.

Visit our Website: http://www.isaacarthur.net.
Join Nebula: https://go.nebula.tv/isaacarthur.
Support us on Patreon: / isaacarthur.
Support us on Subscribestar: https://www.subscribestar.com/isaac-a…
Facebook Group: / 1583992725237264
Reddit: / isaacarthur.
Twitter: / isaac_a_arthur on Twitter and RT our future content.
SFIA Discord Server: / discord.
Credits:
Doomsday Devices & Ontological Weaponry.
Written, Produced & Narrated by: Isaac Arthur.
Editor: Lukas Konecny.
Select imagery/video supplied by Getty Images.
Music by Epidemic Sound: http://nebula.tv/epidemic & Stellardrone.

Chapters.
0:00 Intro.
1:30 Classical Doomsday Devices.
5:57 Cosmic-Scale Doomsday Devices.
11:30 Ontological Weaponry – Breaking Reality.
12:23 The Erasers of History.
16:06 Weapons of Physics Editing.
17:55 Mind and Meaning as Targets.
20:06 Scavenger Hunt.
21:30 Themes and Consequences.
22:55 Practical Considerations & Paradoxes.
24:07 Doomsday Devices vs. Ontological Weapons.
26:48 The Fermi Paradox & Ultimate Destruction.

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