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Category: physics

When Albert Einstein introduced his theory of general relativity in 1915, it changed the way we viewed the universe. His gravitational model showed how Newtonian gravity, which had dominated astronomy and physics for more than three centuries, was merely an approximation of a more subtle and elegant model.

Einstein showed us that gravity is not a mere force but is rather the foundation of cosmic structure. Gravity, Einstein said, defined the structure of space and time itself.

But in the past century, we have learned far more about the cosmos than even Einstein could have imagined. Some of our observations, such as gravitational lensing clearly confirm general relativity, but others seem to poke holes in the model. The rotational motion of galaxies doesn’t match the predictions of gravity alone, leading astronomers to introduce .

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Scientists in Germany have crafted “skyrmion bags” of light—complex vortex-like structures—on the surface of gold by cleverly manipulating how laser beams interact with nano-etched patterns.

This unusual feat not only adds a surprising twist to the physics of light but also hints at future technologies that could break the limits of current microscopes.

Skyrmion light bags: a new breakthrough

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An avalanche is caused by a chain reaction of events. A vibration or a change in terrain can have a cascading and devastating impact.

A similar process may happen when living tissues are subject to being pushed or pulled, according to new research published in Nature Communications, by Northeastern University doctoral student Anh Nguyen and supervised by Northeastern physics professor Max Bi.

As , Bi and Nguyen use and mathematics to understand the mechanical processes that organisms undergo on a cellular level. With this more recent work, they have observed that when subjected to sufficient stress, tissues can “suddenly and dramatically rearrange themselves,” similar to how avalanches are formed in the wild.

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Found in everything from kitchen appliances to sustainable energy infrastructure, stainless steels are used extensively due to their excellent corrosion (rusting) resistance. They’re an important material in many industries, including manufacturing, transportation, oil and gas, nuclear power and chemical processing.

However, stainless steels can undergo a process called sensitization when subjected to a certain range of high temperatures—like during welding—and this substantially deteriorates their resistance. Left unchecked, corrosion can lead to cracking and structural failure.

“This is a major problem for stainless steels,” says Kumar Sridharan, a professor of nuclear engineering and engineering physics and materials science and engineering at the University of Wisconsin–Madison. “When gets corroded, components need to be replaced or remediated. This is an expensive process and causes extended downtime in industry.”

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Understanding the origin of heavy elements on the periodic table is one of the most challenging open problems in all of physics. In the search for conditions suitable for these elements via “nucleosynthesis,” a Los Alamos National Laboratory-led team is going where no researchers have gone before: the gamma-ray burst jet and surrounding cocoon emerging from collapsed stars.

As proposed in an article in The Astrophysical Journal, photons produced deep in the jet could dissolve the outer layers of a star into neutrons, causing a series of physical processes that result in the formation of heavy elements.

“The creation of heavy elements such as uranium and plutonium necessitates extreme conditions,” said Matthew Mumpower, physicist at Los Alamos. “There are only a few viable yet rare scenarios in the cosmos where these elements can form, and all such locations need a copious amount of neutrons. We propose a new phenomenon where those neutrons don’t pre-exist but are produced dynamically in the star.”

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In every scientific discovery in the movies, a scientist observes something unexpected, scratches the side of his or her forehead and says “hmmmmm.” In just such a moment in real life, scientists from Canada observed unexpected flashes of curved green light from a red light-emitting polymer above its surface. The flashes were reminiscent of the colored arcs that auroras take above Earth’s poles, providing a clue as to their provenance.

Their resulting investigation of the new phenomenon could find applications towards understanding the failures of polymer materials and more. Their work has been published in Physical Review Letters.

Jun Gao, a professor and chair of Engineering Physics at the Engineering Physics and Astronomy Department at Queen’s University in Ontario, Canada, and graduate student Dongze Wang were investigating the performance of semiconductors called polymer light-emitting electrochemical cells, or PLECs.

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“This is a very tiny object, with very weak gravity, so it easily loses a lot of mass, which then further weakens its gravity, so it loses even more mass,” said Dr. Avi Shporer.

What can a planet that’s shedding its material teach astronomers about planetary formation and evolution? This is what a recently submitted study to The Astrophysical Journal Letters hopes to address as an international team of scientists investigated a unique exoplanet that orbits its host star approximately 20 times closer than Mercury orbits our Sun, resulting in the exoplanet shedding so much material that it’s creating a tail of debris and will eventually disintegrate into nothing.

“The extent of the tail is gargantuan, stretching up to 9 million kilometers long, or roughly half of the planet’s entire orbit,” said Dr. Marc Hon, who is a postdoc in the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology (MIT) and lead author of the study.

Exoplanet BD+054868Ab is located approximately 140 light-years from Earth and orbits its star in approximately 30.5 hours. For context, Mercury takes our Sun in 88 days. The orbit of BD+054868Ab is so close, astronomers hypothesize that it’s a molten world slowly shedding its material and they estimate it will be completely gone between 1 million and 2 million years from now. During its long and slow death, BD+054868Ab is shedding so material that it’s leaving a trail of debris in its wake, which initially puzzled astronomers after analyzing data obtained from NASA’s Transiting Exoplanet Survey Satellite (TESS).

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Researchers from Max Born Institute have demonstrated a successful way to control and manipulate nanoscale magnetic bits—the building blocks of digital data—using an ultrafast laser pulse and plasmonic gold nanostructures. The findings were published in Nano Letters.

All-optical, helicity-independent magnetization switching (AO-HIS) is one of the most interesting and promising mechanisms for this endeavor, where the magnetization state can be reversed between two directions with a single femtosecond laser pulse, serving as “0s” and “1s” without any or complex wiring. This opens up exciting possibilities for creating memory devices that are not only faster and more robust but also consume far less power.

Ultrafast light-driven control of magnetization on the nanometer-length scale is key to achieving competitive bit sizes in next-generation data storage technology. However, it is currently not well understood to what extent basic physics processes such as at the nanoscale and the propagation of magnetic domain walls limit the minimum achievable bit size.

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Ultrafast light-driven control of magnetization on the nanometer length scale is key to achieve competitive bit sizes in next generation data storage technology. Researchers at Max Born Institute in Berlin and of the large scale facility Elettra in Trieste, Italy, have successfully demonstrated the ultrafast emergence of all-optical switching by generating a nanometer scale grating by interference of two pulses in the extreme ultraviolet spectral range.

The physics of optically driven magnetization dynamics on the femtosecond time scale is of great interest for two main reasons: first, for a deeper understanding of the fundamental mechanisms of nonequilibrium, ultrafast spin dynamics and, second, for the potential application in the next generation of information technology with a vision to satisfy the need for both faster and more energy efficient data storage devices.

All– (AOS) is one of the most interesting and promising mechanisms for this endeavor, where the magnetization state can be reversed between two directions with a single femtosecond laser pulse, serving as “0s” and “1s.” While the understanding of the temporal control of AOS has progressed rapidly, knowledge on ultrafast transport phenomena on the nanoscale, important for the realization of all-optical magnetic reversal in technological applications, has remained limited due to the wavelength limitations of optical radiation. An elegant way to of overcoming these restrictions is to reduce the wavelengths to the extreme ultraviolet (XUV) spectral range in transient grating experiments. This technique is based on the interference of two XUV beams leading to a nanoscale excitation pattern and has been pioneered at the EIS-Timer beamline of the free-electron laser (FEL) FERMI in Trieste, Italy.

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