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Category: particle physics – Page 233

The standard model of particle physics tells us that most particles we observe are made up of combinations of just six types of fundamental entities called quarks. However, there are still many mysteries, one of which is an exotic, but very short-lived, Lambda resonance known as Λ(1405). For a long time, it was thought to be a particular excited state of three quarks—up, down, and strange—and understanding its internal structure may help us learn more about the extremely dense matter that exists in neutron stars.

Investigators from Osaka University were part of a team that has now succeeded in synthesizing Λ(1405) for the first time by combining a K- meson and a proton and determining its complex mass (mass and width). The K− meson is a negatively charged particle containing a strange and an up antiquark. The much more familiar proton that makes up the matter that we are used to has two up quarks and a down quark. The researchers showed that Λ(1405) is best thought of as a temporary bound state of the K- meson and the proton, as opposed to a three-quark .

In their study published recently in Physics Letters B, the group describes the experiment they carried out at the J-PARC accelerator. K− mesons were shot at a deuterium target, each of which had one proton and one neutron. In a successful reaction, a K− meson kicked out the neutron, and then merged with the proton to produce the desired Λ(1405).

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Starting with the emergence of quantum mechanics, the world of physics has been divided between classical and quantum physics. Classical physics deals with the motions of objects we typically see every day in the macroscopic world, while quantum physics explains the exotic behaviors of elementary particles in the microscopic world.

Many solids or liquids are composed of particles interacting with one another at close distances, which sometimes results in the rise of “quasiparticles.” Quasiparticles are long-lived excitations that behave effectively as weakly interacting particles. The idea of quasiparticles was introduced by the Soviet physicist Lev Landau in 1941, and ever since has been highly fruitful in quantum matter research. Some examples of quasiparticles include Bogoliubov quasiparticles (i.e. “broken Cooper pairs”) in superconductivity, excitons in semiconductors, and phonons.

Examining emergent collective phenomena in terms of quasiparticles provided insight into a wide variety of physical settings, most notably in superconductivity and superfluidity, and recently in the famous example of Dirac quasiparticles in graphene. But so far, the observation and use of quasiparticles have been limited to : in classical condensed matter, the collision rate is typically much too high to allow long-lived particle-like excitations.

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What is behind dark energy—and what connects it to the cosmological constant introduced by Albert Einstein? Two physicists from the University of Luxembourg point the way to answering these open questions of physics.

The universe has a number of bizarre properties that are difficult to understand with everyday experience. For example, the matter we know, consisting of atoms and molecules and other particles, apparently makes up only a small part of the energy density of the universe. The largest contribution, more than two-thirds, comes from “”—a hypothetical form of energy whose background physicists are still puzzling over.

Moreover, the universe is not only expanding steadily, but also doing so at an ever-faster pace. Both characteristics seem to be connected, because dark energy is also considered a driver of accelerated expansion. Moreover, it could reunite two powerful physical schools of thought: and the developed by Albert Einstein. But there is a catch: calculations and observations have so far been far from matching. Now two researchers from Luxembourg have shown a way to solve this 100-year-old riddle in a paper published by Physical Review Letters.

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Controlling the trajectory of a basketball is relatively straightforward, as it only requires the application of mechanical force and human skill. However, controlling the movement of quantum systems like atoms and electrons poses a much greater challenge. These tiny particles are prone to perturbations that can cause them to deviate from their intended path in unexpected ways. Additionally, movement within the system degrades, known as damping, and noise from environmental factors like temperature further disrupts its trajectory.

To counteract the effects of damping and noise, researchers from Okinawa Institute of Science and Technology (OIST) in Japan have found a way to use artificial intelligence to discover and apply stabilizing pulses of light or voltage with fluctuating intensity to quantum systems. This method was able to successfully cool a micro-mechanical object to its quantum state and control its motion in an optimized way. The research was recently published in the journal Physical Review Research.

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Approximately 85% of the mass of our galaxy is comprised by dark matter, matter that does not emit, absorb or reflect light and thus cannot be directly observed. While several studies have hinted at or theorized about its composition, it remains one of the greatest unresolved physics problems.

Physicists all over the world have been conducting dark matter searches or trying to come up with new methods to directly observe different dark matter candidates. One hypothetical form of dark matter that has so far eluded detection is dark-photon dark matter.

An intriguing possibility is that dark matter is comprised of dark photons, which resemble photons (i.e., the particles that make up visible light), but interact with charges with feeble strength. These dark photons could theoretically have masses in the milli-electrovolt range, approximately a million times lighter than those of electrons and thus notoriously difficult to detect.

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With so much death all around us, from the pandemic to the war in Ukraine to all the mass shootings, you might wonder what it all means. Queen Elizabeth gone. Betty White gone. And perhaps even a loved one of yours gone. They no longer exist, right? They are just memories, at least from a rational scientific perspective. But what if you’re wrong?

Dr. Caroline Soames-Watkins also believed that the world around her existed as a hard, cold reality ticking away like a clock. Death was a foregone conclusion—until she learned different. Caro, the protagonist of my new novel co-written with award-winning sci-fi author Nancy Kress, also thought she had the world figured out. Not her personal world, which has been upended by controversy, but how the physical world works and how her consciousness operates within it. Broke and without a job, she accepts a job offer from her great-uncle, a Nobel Prize-winning scientist who runs a research facility studying the space between biology and consciousness—between the self and what we assume is reality. They are on the verge of a humanity-altering discovery, which throws Caro into danger—love, loss, and death—that she could never have imagined possible.

Observer takes Caro on a mind-expanding journey to the very edge of science, challenging her to think about life and the power of the imagination in startling new ways. The ideas behind Observer are based on real science, starting with the famous two-slit experiments, in which the presence of an observer affects the path taken by a sub-atomic particle, and moves step-by-step into cutting-edge science about quantum entanglement, on-going experiments applying quantum-level physics to the macro-world, the multiverse, and the nature of time and consciousness itself.

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Inspired by sea cucumbers, engineers have designed miniature robots that rapidly and reversibly shift between liquid and solid states. On top of being able to shape-shift, the robots are magnetic and can conduct electricity. The researchers put the robots through an obstacle course of mobility and shape-morphing tests in a study publishing January 25 in the journal Matter.

Where traditional robots are hard-bodied and stiff, “soft” robots have the opposite problem; they are flexible but weak, and their movements are difficult to control. “Giving robots the ability to switch between liquid and solid states endows them with more functionality,” says Chengfeng Pan (@ChengfengPan), an engineer at The Chinese University of Hong Kong who led the study.

The team created the new phase-shifting material—dubbed a “magnetoactive solid-liquid phase transitional machine”—by embedding magnetic particles in gallium, a metal with a very low melting point (29.8 °C).

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Virus-enveloping macromolecular shells or tilings can prevent viruses from entering cells. Here, we describe the design and assembly of a cone-shaped DNA origami higher-order assembly that can engulf and tile the surface of pleomorphic virus samples larger than 100 nm. We determine the structures of subunits and of complete cone assemblies using cryoelectron microscopy (cryo-EM) and establish stabilization treatments to enable usage in in vivo conditions. We use the cones exemplarily to engulf influenza A virus particles and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), chikungunya, and Zika virus-like particles. Depending on the relative dimensions of cone to virus particles, multiple virus particles may be trapped per single cone, and multiple cones can also tile and adapt to the surface of aspherical virus particles. The cone assemblies form with high yields, require little purification, and are amenable for mass production, which is a key requirement for future real-world uses including as a potential antiviral agent.

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