Listening to starquakes Artistic impression of acoustic waves in the interior of a star. Red and blue represent displacements in opposite directions. (Courtesy: ESO)
Stars are cosmic musical instruments: they vibrate with complex patterns that echo through their interiors. These vibrations, known as pressure waves, ripple through the star, similar to the earthquakes that shake our planet. The frequencies of these waves hold information about the star’s mass, age and internal structure.
QUANTUM PHENOMENA AND HUMAN CIVILIZATION: Exploring the Intersection of Quantum Physics and Its Impact on Technology, Society, and Culture Kindle Edition
This episode of the Physics World Weekly podcast comes from
the Chicago metropolitan area – a scientific powerhouse that is home to
two US national labs and some of the country’s leading universities.
Physics World’s Margaret Harris was there recently and met Nadya Mason. She is dean of the Pritzker School of Molecular Engineering at the University of Chicago, which focuses on quantum engineering; materials for sustainability; and immunoengineering. Mason explains how molecular-level science is making breakthroughs in these fields and she talks about her own research on the electronic properties of nanoscale and correlated systems.
Harris also spoke to Jeffrey Spangenberger who leads the Materials Recycling Group at Argonne National Laboratory, which is on the outskirts of Chicago. Spangenberger talks about the challenges of recycling batteries and how we could make it easier to recover materials from batteries of the future. Spangenberger leads the ReCell Center, a national collaboration of industry, academia, and national laboratories advancing recycling technologies along the entire battery life cycle.
Carbon layers Artist’s impression of two graphene layers before a twist is applied. (Courtesy: Shutterstock/Rost9)
By adapting their quantum twisting microscope to operate at cryogenic temperatures, researchers have made the first observations of a type of phonon that occurs in twisted bilayer graphene. These “phasons” could have implications for the electron dynamics in these materials.
Graphene is a layer of carbon just one atom thick and it has range of fascinating and useful properties – as do bilayer and multilayer versions of graphene. Since 2018, condensed-matter physicists have been captivated by the intriguing electron behaviour in two layers of graphene that are rotated relative to each other.
Diagram showing the bilayer geometry Δ represents the potential energy offset between the two layers; J∥ and J⊥ are the intra-layer and interlayer magnetic coupling energy respectively; and t∥ represents the intra-layer atom hopping energy. (Courtesy: Henning Schlömer and colleagues)
A proposed experiment that would involve trapping atoms on a two-layered laser grid could be used to study the mechanism behind high-temperature superconductivity. Developed by physicists in Germany and France led by Henning Schlömer the new techniques could revolutionize our understanding of high-temperature superconductivity.
Superconductivity is a phenomenon characterized by an abrupt drop to zero of electric resistance when certain materials are cooled below a critical temperature. It has remained in the physics zeitgeist for over a hundred years and continues to puzzle contemporary physicists. While scientists have a good understanding of “conventional” superconductors (which tend to have low critical temperatures), the physics of high-temperature superconductors remains poorly understood. A deeper understanding of the mechanisms responsible for high-temperature superconductivity could unveil the secrets behind macroscopic quantum phenomena in many-body systems.
Microscale brain sensor The tiny sensor enables thought control of external devices, even during intense motion. (Courtesy: W Hong Yeo)
Brain–computer interfaces (BCIs) enable the flow of information between the brain and an external device such as a computer, smartphone, or robotic limb. Applications range from use in augmented and virtual reality (AR and VR) to restoring function to people with neurological disorders or injuries.
Electroencephalography (EEG)-based BCIs use sensors on the scalp to noninvasively record electrical signals from the brain and decode them to determine the user’s intent. Currently, however, such BCIs require bulky, rigid sensors that prevent use during movement and don’t work well with hair on the scalp, which affects the skin–electrode impedance. A team at Georgia Tech’s WISH Center has overcome these limitations by creating a brain sensor that’s small enough to fit between strands of hair and is stable even while the user is moving.
Repulsive gravity at the quantum scale would have flattened out inhomogeneities in the early universe
First light:
The cosmic microwave background, as imaged by the European Space
Agency’s Planck mission. (Courtesy: ESA and the Planck Collaboration)
In classical physics, gravity is universally attractive. At the quantum level, however, this may not always be the case. If vast quantities of matter are present within an infinitesimally small volume – at the centre of a black hole, for example, or during the very earliest moments of the universe – spacetime becomes curved at scales that approach the Planck length. This is the fundamental quantum unit of distance, and is around 1020 times smaller than a proton.
In these extremely curved regions, the classical theory of gravity – Einstein’s general theory of relativity – breaks down. However, research on loop quantum cosmology offers a possible solution. It suggests that gravity, in effect, becomes repulsive. Consequently, loop quantum cosmology predicts that our present universe began in a so-called “cosmic bounce”, rather than the Big Bang singularity predicted by general relativity.
In a recent paper published in EPL, Edward Wilson-Ewing, a mathematical physicist at the University of New Brunswick, Canada, explores the interplay between loop quantum cosmology and a phenomenon sometimes described as “the echo of the Big Bang”: the cosmic microwave background (CMB). This background radiation pervades the entire visible universe, and it stems from the moment the universe became cool enough for neutral atoms to form. At this point, light could suddenly travel through space without being continually scattered by the plasma of electrons and light nuclei that existed before. This freshly liberated light makes up the CMB, so studying it offers clues to the early universe.
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