For the first time ever, researchers have successfully trapped individual atoms of krypton to create a one-dimensional gas.
Category: particle physics – Page 155
What is the universe made of? This question has driven astronomers for hundreds of years.
For the past quarter of a century, scientists have believed “normal” stuff like atoms and molecules that make up you, me, Earth, and nearly everything we can see only accounts for 5% of the universe. Another 25% is “dark matter”, an unknown substance we can’t see but which we can detect through how it affects normal matter via gravity.
The remaining 70% of the cosmos is made of “dark energy”. Discovered in 1998, this is an unknown form of energy believed to be making the universe expand at an ever-increasing rate.
In physics, scientists have been fascinated by the mysterious behavior of superconductors—materials that can conduct electricity with zero resistance when cooled to extremely low temperatures. Within these superconducting systems, electrons team up in “Cooper pairs” because they’re attracted to each other due to vibrations in the material called phonons.
As a thermodynamic phase of matter, superconductors typically exist in an equilibrium state. But recently, researchers at JILA became interested in kicking these materials into excited states and exploring the ensuing dynamics. As reported in a new Nature paper, the theory and experiment teams of JILA and NIST Fellows Ana Maria Rey and James K. Thompson, in collaboration with Prof. Robert Lewis-Swan at the University of Oklahoma, simulated superconductivity under such excited conditions using an atom-cavity system.
Instead of dealing with actual superconducting materials, the scientists harnessed the behavior of strontium atoms, laser-cooled to 10 millionths of a degree above absolute zero and levitated within an optical cavity built out of mirrors.
It’s all thanks to what is called the “solar maximum,” when the sun is reaching its peak of a roughly 11-year cycle, which NASA says began again in December 2019. The sun’s activity has been ramping up since then, with an expected peak in July 2025.
MORE: Pilot performs mid-flight maneuver to give passengers a rare view of the northern lights
The northern lights, also known as the aurora borealis, happen in regions around the earth’s magnetic pole. They appear when electrons from solar flares interact with atoms and molecules in the Earth’s atmosphere. That in turn creates lights and multiple colors in the sky.
A radical theory that consistently unifies gravity and quantum mechanics while preserving Einstein’s classical concept of spacetime is announced today in two papers published simultaneously by UCL (University College London) physicists.
Modern physics is founded upon two pillars: quantum theory on the one hand, which governs the smallest particles in the universe, and Einstein’s theory of general relativity on the other, which explains gravity through the bending of spacetime. But these two theories are in contradiction with each other and a reconciliation has remained elusive for over a century.
The prevailing assumption has been that Einstein’s theory of gravity must be modified, or “quantised”, in order to fit within quantum theory. This is the approach of two leading candidates for a quantum theory of gravity, string theory and loop quantum gravity.
The use of NISQ devices for useful quantum simulations of materials and chemistry is still mainly limited by the necessary circuit depth. Here, the authors propose to combine classically-generated effective Hamiltonians, hybrid fermion-to-qubit mapping and circuit optimisations to bring this requirement closer to experimental feasibility.
The power of gravity is writ large across our visible universe. It can be seen in the lock step of moons as they circle planets; in wandering comets pulled off-course by massive stars; and in the swirl of gigantic galaxies. These awesome displays showcase gravity’s influence at the largest scales of matter. Now, nuclear physicists are discovering that gravity also has much to offer at matter’s smallest scales.
New research conducted by nuclear physicists at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility is using a method that connects theories of gravitation to interactions among the smallest particles of matter to reveal new details at this smaller scale. The research has now revealed, for the first time, a snapshot of the distribution of the strong force inside the proton. This snapshot details the shear stress the force may exert on the quark particles that make up the proton. The result was recently published in Reviews of Modern Physics.
According to the lead author on the study, Jefferson Lab Principal Staff Scientist Volker Burkert, the measurement reveals insight into the environment experienced by the proton’s building blocks. Protons are built of three quarks that are bound together by the strong force.
This self-assembling ‘metallaknot’ of gold emerged when gold acetylide was combined with a carbon structure known as a diphosphine ligand.
Since 1989, chemists have been exploring ways to tie molecular knots using metal ions to guide helical chains into specific configurations. These knots are typically secured by the presence of metal atoms, which are removed at the end of the process to prevent untying.
However, the self-assembly of the new gold knot suggests a different mechanism at play, one that even the researchers, including chemist Richard Puddephatt from the University of Western Ontario, find mysterious.
Astronomers analyzing 13 years of data from NASA’s Fermi Gamma-ray Space Telescope have found an unexpected and as yet unexplained feature outside of our galaxy.
“It is a completely serendipitous discovery,” said Alexander Kashlinsky, a cosmologist at the University of Maryland and NASA’s Goddard Space Flight Center in Greenbelt, who presented the research at the 243rd meeting of the American Astronomical Society in New Orleans. “We found a much stronger signal, and in a different part of the sky, than the one we were looking for.”
Intriguingly, the gamma-ray signal is found in a similar direction and with a nearly identical magnitude as another unexplained feature, one produced by some of the most energetic cosmic particles ever detected.
Light can behave in strange ways when it interacts with materials. For example, in a photonic material that consists of periodic arrangements of nanoscale optical cavities, light can slow to a crawl or even stop altogether. Theorists have explained this phenomenon for some of these photonic “metacrystals” using the simplifying assumption that the light in each cavity interacts only with the light in its nearest neighbor cavities. But recent observations of photonic metacrystals with larger unit cells suggest that longer-range interactions should also be considered. Now Thanh Xuan Hoang at the Agency for Science, Technology and Research in Singapore and collaborators have theoretically confirmed the importance of long-range interactions for slowing or stopping light in a one-dimensional photonic metacrystal [1]. The team says that the finding could be used to help researchers design nanoparticle arrays for analog image processing and optical computing.
For their study, Hoang and his collaborators modeled the light–matter interactions within a row of identical dielectric nanoparticles whose diameters were similar to the wavelength of the light. Such a system is relatively tractable with precise solutions, making it a useful tool for investigating the long-range effects hinted at by recent experiments.
When the researchers extended their one-dimensional system to hundreds of nanoparticles, they found that they could collectively excite the particles by oscillating a nearby electric dipole. The resulting system displayed a resonant state that slowed a specific wavelength of light. This outcome occurred only when long-range interactions between particles were permitted. Hoang likens the dipolar emitter to the conductor of an orchestra and the particles to musicians. The nanoparticles harmonize under the conductor’s direction to create a cohesive piece, he says.