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Category: particle physics

Cutting a photon in two creates an infinite swarm of particles

By definition, elementary particles can’t be broken into smaller pieces. But in a new theoretical study published in Physical Review Letters, Johannes Skaar and colleagues have revealed what would happen if you tried anyway for a single photon. The answer is deeply strange: attempting to cut a photon in two wouldn’t produce two smaller photons, but instead conjure an infinite number of them out of thin air.

Like any quantum particle, a photon exists simultaneously as a single, localized particle, and an extended wave, spread out across space. For their investigation, Skaar’s team considered what would happen if a single photon passed through an optical shutter—essentially a very fast mirror that can be switched on and off to block part of a pulse of light. If the shutter was fast enough, it could intercept the photon mid-pulse, snipping off part of this extended wave.

To find out what would happen afterward, the researchers applied quantum equations that describe how the photon’s underlying electromagnetic field behaves at the quantum level. Specifically, their analysis tracked precisely how the photon’s quantum state would be transformed by the shutter’s intervention.

Molecular glasses solve long-standing Arrhenius paradox

Glasses are non-crystalline but solid states of matter in which molecules and atoms are not arranged into a regular crystal lattice, but rather in a disordered pattern. Glassy materials are widely used in various settings, for instance, in the synthesis of pharmaceuticals and the development of electronics or optical devices.

When studying movement and changes in various materials and substances, physicists commonly rely on the so-called Arrhenius model. This is a mathematical framework introduced by Svante Arrhenius in 1889, which can be used to calculate how temperature affects the speed of a heat-activated chemical reaction or physical process.

Past studies have shown that when the Arrhenius model is applied to molecular glasses, it yields unrealistically small pre-exponential factors. Pre-exponential factors are values that describe the intrinsic timescale of the movement of molecules without considering temperature effects.

Atomic reshuffle leads to record-breaking catalysts for hydrogen production

Researchers have discovered that atoms can be mixed, separated, and recombined within the same experiment, providing a pathway to a record-breaking catalyst for green hydrogen production. In their study, the team created nanoscale particles containing only a few dozen platinum and nickel atoms and observed unusual dynamic behavior in direct space and in real time. As the two metals separate from one another while maintaining an interface, they become highly active for electrochemical water splitting, leading to efficient hydrogen evolution.

The project was led by the University of Nottingham in collaboration with the University of Birmingham, Diamond Light Source, and Ulm University in Germany. The study appears in Advanced Materials.

Research team leader Dr. Jesum Alves Fernandes, from the School of Chemistry, University of Nottingham, said, “What makes this discovery exciting is that we can reversibly tune the structure of the particle while directly observing the process at the atomic scale. This opens a new strategy for designing adaptive catalysts for a wide range of applications.”

Violent rocket particles could reshape future spacecraft design

When rockets fire into space, the insides of their engines become an extreme environment where temperatures soar and tiny particles are thrown around at hypersonic speeds. These particles behave in ways that break long-held assumptions, according to new research that could help improve the durability, safety and performance of future space and defense technologies.

The study shows that particles traveling at hypersonic speeds do not remain spherical, instead melting and deforming mid-flight in ways that change how heat, drag and energy move through rocket systems. The findings, published in Physics of Fluids, have led researchers to develop a new drag model that more accurately predicts particle behavior under extreme conditions.

The work was led by researchers from the Southeast University–Monash University Joint Research Institute, Monash University and Shanghai University.

Smaller nanoplastics trigger stronger changes in brain neuron activity

Smaller plastic particles have more effects on neurons, the key information processing cells of the brain, new research from the University of Eastern Finland shows. In the study, neuronal cells were exposed to polystyrene nanoplastics at low doses to study subtle changes.

Plastic production continues to rise, despite worldwide concerns. In addition to environmental implications, there is an increasing interest in how exposure to plastics may impact human health, but our understanding is still limited. Only recently it was shown that plastics can accumulate also in the human brain.

Plastic particles smaller than 5,000 nm in diameter are called microplastics, and the smallest plastic particles with a diameter of less than 1,000 nm are called nanoplastics. The small size of nanoplastics enables them to interact with various cell types, and other particles or biological mass, such as bacteria. Compared to microplastics, nanoplastics have larger adsorption capacity and penetrate through biological barriers more easily. This makes them potentially more harmful and a compelling target for research in the field of neurobiology.

The impact of nanoplastics on neurons may depend on their size

Smaller plastic particles have more effects on neurons, the key information processing cells of the brain, new research from the University of Eastern Finland shows. In the study, neuronal cells were exposed to polystyrene nanoplastics at low doses to study subtle changes.

The study is published in the journal NanoImpact.

Plastic production continues to rise, despite worldwide concerns. In addition to environmental implications, there is an increasing interest in how exposure to plastics may impact human health, but our understanding is still limited. Only recently was it shown that plastics can also accumulate in the human brain.

Matter may entangle with light far more easily near quantum critical points

Quantum entanglement is a state in which particles are entwined with each other. In this entwined state, the properties of one particle influence the other, even when they aren’t physically close to each other. This phenomenon has often been observed in small quantum systems with only a few particles in them, where researchers can use it to store and process quantum information. Rice University professor Qimiao Si is interested in understanding and applying quantum entanglement to macroscopic systems with vast numbers of particles.

In a paper recently published in Nature Communications, Si described a method that could lead to not only better understanding of quantum entanglement in quantum materials but also more ready usage of quantum entanglement in macroscopic systems. His theory posits this can be done by coupling quantum materials to quantum light.

“In this theory, by placing matter in a small mirrored cavity and pushing it towards what is called the quantum critical point, we can then introduce photons and induce quantum entanglement in the photon-matter hybrid,” said Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy and director of the Extreme Quantum Materials Alliance.

Space station dust maps slash climate uncertainty over iron-rich particles

New research from a team of scientists led by Cornell is transforming how researchers understand one of the atmosphere’s most abundant and least understood constituents: mineral dust.

Mineral dust, composed of tiny particles lifted from arid regions including the Sahara, Middle East and East Asia, plays a complex role in Earth’s climate system. These particles both scatter and absorb radiation, influence cloud formation and even fertilize ecosystems. But until recently, scientists lacked reliable global data on the surface soils’ mineral composition, particularly on the prevalence of light-absorbing iron oxides.

Using high-resolution data from a NASA mission aboard the International Space Station, the team has reduced long-standing uncertainty about how airborne dust particles affect Earth’s energy balance through interactions with sunlight. The findings are published in the journal Nature Geoscience.

Better math discriminates exotic from classical materials

The planar Hall effect is a tabletop diagnostic tool for special quantum properties useful in basic research and technological applications. Or so it was thought, because careful calculation by Kobe University researchers clarifies the conditions under which this effect may also appear in classical materials. This makes the diagnostic more meaningful and enables more purposeful design.

In the hunt for materials with properties that are useful for quantum computing or spintronics, researchers have used the “planar Hall effect” as a tabletop diagnostic tool: The researchers send a current through a thin, flat sample and observe whether an electric voltage is produced in response to a magnetic field in the same plane as the sample.

If it is, the pattern of how the voltage responds to rotating the magnetic field in the plane of the sample tells researchers about the properties of the material.

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