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Category: particle physics – Page 222

The ancient Greek philosopher Aristotle wrote in his manuscript on Physics 2,373 years ago: “If everything that exists has a place, place too will have a place, and so on ad infinitum.” Is the notion of space being continuous ‘without limit’ justified?

Before elementary particles were discovered, water was thought to be a continuous fluid. This is a good approximation on large scales but not on molecular scales where the interactions among elementary particles matter.

Similarly, spacetime has been thought to be a continuum since ancient times. While this notion appears consistent with all experimental data on large spatial or temporal scales, it may not be valid on tiny scales where quantum effects of gravity matter. An analogy can be made with the illusion of a movie which appears continuous when the frame rate is high enough and the spatial pixels are small enough for our brain to process the experience as seamless. Since our brain is made of elementary particles, the temporal and spatial resolution by which it senses reality is coarser by many orders of magnitude than any fundamental scale by which spacetime is discretized.

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While optics and mechanics are two distinct branches of physics, they are connected. It is well known that the geometrical/ray treatment of light has direct analogies to mechanical descriptions of particle motion. However, connections between coherence wave optics and classical mechanics are rarely reported. Here we report links of the two through a systematic quantitative analysis of polarization and entanglement, two optical coherence properties under the wave description of light pioneered by Huygens and Fresnel. A generic complementary identity relation is obtained for arbitrary light fields. More surprisingly, through the barycentric coordinate system, optical polarization, entanglement, and their identity relation are shown to be quantitatively associated with the mechanical concepts of center of mass and moment of inertia via the Huygens-Steiner theorem for rigid body rotation.

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Since the 17th century, when Isaac Newton and Christiaan Huygens first debated the nature of light, scientists have been puzzling over whether light is best viewed as a wave or a particle—or perhaps, at the quantum level, even both at once. Now, researchers at Stevens Institute of Technology have revealed a new connection between the two perspectives, using a 350-year-old mechanical theorem—ordinarily used to describe the movement of large, physical objects like pendulums and planets—to explain some of the most complex behaviors of light waves.

The work, led by Xiaofeng Qian, assistant professor of physics at Stevens and reported in the August 17 online issue of Physical Review Research, also proves for the first time that a light wave’s degree of non-quantum entanglement exists in a direct and complementary relationship with its degree of polarization. As one rises, the other falls, enabling the level of entanglement to be inferred directly from the level of polarization, and vice versa. This means that hard-to-measure such as amplitudes, phases and correlations—perhaps even these of quantum wave systems—can be deduced from something a lot easier to measure: .

“We’ve known for over a century that light sometimes behaves like a wave, and sometimes like a particle, but reconciling those two frameworks has proven extremely difficult,” said Qian “Our work doesn’t solve that problem—but it does show that there are profound connections between wave and particle concepts not just at the , but at the level of classical light-waves and point-mass systems.”

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Researchers at the University of Ottawa, in collaboration with Danilo Zia and Fabio Sciarrino from the Sapienza University of Rome, recently demonstrated a novel technique that allows the visualization of the wave function of two entangled photons, the elementary particles that constitute light, in real-time.

Using the analogy of a pair of shoes, the concept of entanglement can be likened to selecting a shoe at random. The moment you identify one shoe, the nature of the other (whether it is the left or right shoe) is instantly discerned, regardless of its location in the universe. However, the intriguing factor is the inherent uncertainty associated with the identification process until the exact moment of observation.

The , a central tenet in , provides a comprehensive understanding of a particle’s . For instance, in the shoe example, the “wave function” of the shoe could carry information such as left or right, the size, the color, and so on.

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Researchers have developed “smart rust,” iron oxide nanoparticles that clean water by attracting pollutants such as oil, nano-and microplastics, glyphosate, and even estrogen hormones.

Pouring flecks of rust into water typically makes it dirtier. However, a groundbreaking development by researchers has led to the creation of “smart rust,” a type of iron oxide nanoparticle that can purify water. This smart rust has the unique ability to attract various pollutants, such as oil, nano-and microplastics, and the herbicide glyphosate, depending on the particles’ coating. What makes it even more efficient is its magnetic nature, which allows easy removal from water using a magnet, taking the pollutants along with it. Recently, the team has optimized these particles to capture estrogen hormones, which can be detrimental to aquatic life.

Presentation and Significance.

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Upcoming gravitational-wave observatories could find evidence of a new type of neutrino, supporting a popular theory for why matter dominates over antimatter.

Many cosmologists look to a model called the seesaw mechanism to explain both the Universe’s preponderance of matter over antimatter and why the three flavors of neutrinos are so light. The seesaw mechanism resolves these big questions by introducing a yet-unobserved particle known as a sterile neutrino, which is far more massive than the known neutrino flavors. In new theoretical work, Graham White of TRIUMF, Canada, and colleagues propose a method to test the model indirectly using gravitational-wave observatories due to come online in the next decade and beyond. Direct observation is impossible for now, as producing sterile neutrinos experimentally would require a particle accelerator many orders of magnitude more powerful than the Large Hadron Collider.

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The state, known as the Machida-Shibata state, involves the pairing of electrons in an artificial atom on the surface of a superconductor.

A team of physicists from Hamburg University has made a breakthrough in the field of quantum physics by observing a rare state of matter that was predicted by Japanese theorists more than half a century ago.

Credits: EzumeImages/iStock.

Machida-Shibata state.

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A “demon” particle that has been haunting physicists for nearly 70 years has been found in an experiment by American researchers.

It is not a particle in the traditional sense like a proton or electron. It is a “composite” particle made up of a combination of electrons, in a solid.

In 1956, theoretical physicist David Pines predicted that electrons in a solid could do something strange. Electrons have both mass and charge. But Pines asserted that combinations of electrons in a solid could form a composite particle that is massless, has no charge and does not interact with light.

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In a recent Science paper, researchers led by JILA and NIST Fellow Jun Ye, along with collaborators JILA and NIST Fellow David Nesbitt, scientists from the University of Nevada, Reno, and Harvard University, observed novel ergodicity-breaking in C60, a highly symmetric molecule composed of 60 carbon atoms arranged on the vertices of a “soccer ball” pattern (with 20 hexagon faces and 12 pentagon faces).

Their results revealed ergodicity breaking in the rotations of C60. Remarkably, they found that this ergodicity breaking occurs without symmetry breaking and can even turn on and off as the molecule spins faster and faster. Understanding ergodicity breaking can help scientists design better-optimized materials for energy and heat transfer.

Many everyday systems exhibit “ergodicity” such as heat spreading across a frying pan and smoke filling a room. In other words, matter or energy spreads evenly over time to all system parts as energy conservation allows. On the other hand, understanding how systems can violate (or “break”) ergodicity, such as magnets or superconductors, helps scientists understand and engineer other exotic states of matter.

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