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Category: particle physics – Page 49

In a groundbreaking study published in Nature, scientists from JILA—a partnership between the National Institute of Standards and Technology and the University of Colorado Boulder—have managed to measure time dilation at an unprecedentedly small scale. This breakthrough involved detecting time differences between two clocks spaced only a millimeter apart, a distance as small as the width of a pencil tip. The experiment marks a major step forward in the precision of atomic clocks and sheds new light on the effects of gravity on time as outlined in Albert Einstein’s theory of general relativity.

Clocks that Measure the Effects of Gravity at the Millimeter Scale

Time dilation, a phenomenon where time moves more slowly in strong gravitational fields or at high speeds, was first predicted by Einstein’s relativity theory. JILA researchers, led by physicist Jun Ye, used highly precise atomic clocks in this experiment to measure these differences in gravitational time dilation over millimeter distances. By tracking frequency shifts among a sample of 100,000 ultra-cold strontium atoms held in a lattice, the team achieved a remarkable level of control, detecting how the gravitational pull from Earth slightly altered the passage of time over even this small distance.

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During the time you read this article, something will happen in the sky that many scientists didn’t believe would happen until recently. NASA says that a magnetic doorway will open that will connect the Earth and the Sun, which are 150 million kilometers apart.

Hundreds of thousands of high-energy particles will pass through this gap until it closes, which will happen about the time you reach the bottom of the page.

NASA’s Goddard Space Flight Center’s space physicist David Seebeck calls it a “flux transfer event” or “FTE.” “In 1998, I was sure they didn’t exist, but the proof is now clear.” In fact, David Seebeck proved their existence in 2008 at a plasma conference in Huntsville, Alabama, when he told a group of space physicists from all over the world about his research.

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Advancements in nuclear physics suggest the possibility of discovering stable, superheavy elements.

Researchers have found an alternative way to produce atoms of the superheavy element livermorium. The new method opens up the possibility of creating another element that could be the heaviest in the world so far: number 120.

The search for new elements is driven by the goal of finding versions that are stable enough to exist beyond a fleeting moment. In nuclear physics, there is a concept known as the “island of stability”—a hypothetical region in the upper reaches of the periodic table where as-yet-undiscovered superheavy elements could potentially last longer than just a few seconds. Scientists are working to explore how far the stability of atomic nuclei can extend.

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Electrons spin even without an electric charge and this motion in condensed matter constitutes spin current, which is attracting a great deal of attention for next-generation technology such as memory devices. An Osaka Metropolitan University-led research group has been able to gain further insight into this important topic in the field of spintronics.

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Quantum computers hold the promise to emulate complex materials, helping researchers better understand the physical properties that arise from interacting atoms and electrons. This may one day lead to the discovery or design of better semiconductors, insulators, or superconductors that could be used to make ever faster, more powerful, and more energy-efficient electronics.

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The temperature of elementary particles has been observed in the radioactive glow following the collision of two neutron stars and the birth of a black hole. This has, for the first time, made it possible to measure the microscopic, physical properties in these cosmic events.

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For the first time, EPFL researchers have directly observed molecules engaging in hydrogen bonds within liquid water, capturing electronic and nuclear quantum effects that had previously been accessible only through theoretical simulations.

Water is synonymous with life, but the dynamic, multifaceted interaction that brings H2O molecules together – the hydrogen bond – remains mysterious. These hydrogen bonds form as hydrogen and oxygen atoms from neighboring water molecules connect, exchanging electronic charge in the process.

This charge-sharing is a key feature of the three-dimensional ‘H-bond’ network that gives liquid water its unique properties, but quantum phenomena at the heart of such networks have thus far been understood only through theoretical simulations.

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Why are there atomic clocks but no nuclear clocks? After all, an atom’s nucleus is typically surrounded by many electrons, so in principle it should be less susceptible to outside noise (in the form of light). A nucleus, for high-atomic number atoms, contains more particles than does the element’s electrons. It holds nearly the entire mass of the atom while taking up only about 1/100,000th of the atom’s space. While the first atomic clock was invented in 1949, no nuclear clock has yet been feasible.

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Breaking the problem into pieces makes it easier to design a fusion reactor’s coils for optimum energy confinement.

In magnetic-confinement fusion, different reactor designs pose different trade-offs. Stellarators use external magnetic fields to confine plasma in the shape of a twisted donut. Such fields are relatively easy to maintain in a steady state, but optimizing their geometry to minimize energy loss is much more difficult. Tokamaks, in contrast, confine plasma in an axisymmetric geometry using magnetic fields partially generated via currents induced in the plasma. This geometry provides near-perfect confinement at the expense of stability and operational simplicity. José Luis Velasco of Spain’s Center for Energy, Environmental and Technological Research (CIEMAT) and his colleagues now present a new family of stellarator magnetic-field configurations that benefit from tokamak-like energy confinement [1].

Magnetic fusion designs achieve confinement using nested magnetic-flux surfaces. Ideally, each charged particle remains tied to a given surface contour and the plasma as a whole exhibits near-zero radial drift. Such a condition results in perfect confinement, aside from losses due to collisions among particles on the same contour. Tokamaks inherently avoid radial drift, but to achieve the same level of confinement in a stellarator means imposing constraints on each magnetic surface’s topology, sometimes requiring infeasible coil designs.

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A light beam with orbital angular momentum can produce the rotational analog of the Doppler effect on an ion.

A vortex light beam is one whose wave fronts rotate like a corkscrew, endowing the beam with orbital angular momentum. An atom subjected to this beam experiences the usual kick in the direction of the beam’s propagation but also a weaker, sideways kick from the beam’s orbital angular momentum. The Doppler effect causes a moving atom to absorb light at wavelengths that are shifted with respect to those of a stationary atom. Consequently, the sideways kick from a vortex beam can produce what is called a rotational Doppler effect (RDE) in an atom. Nicolás Nuñez Barreto of the University of Buenos Aires in Argentina and his collaborators have now characterized the RDE produced by infrared (IR) vortex beams on a single trapped calcium ion [1].

The researchers used IR lasers to drive a particular transition between electronic levels of the ion in a magnetic field. Two additional IR lasers created two identical copropagating vortex beams whose wavelengths could be adjusted. Thanks to the copropagation and the nature of the transition, the linear Doppler effects of the two beams canceled out. Only when the ion received different sideways kicks resulting from the beams’ unequal angular momenta did it absorb photons, revealing the presence and strength of the RDE.

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