Abra Science

  The linear response theory developed in this work provides a full characterization of the relation between output and input signals (indicated by green and yellow arrows, respectively) in terms of the eigenmodes and the canonical states of the underlying non-Hermitian Hamiltonian. Credit: Ramy El-Ganainy Linear analysis plays a central role in science and engineering. Even when dealing with nonlinear systems, understanding the linear response is often crucial for gaining insight into the underlying complex dynamics. In recent years, there has been a great interest in studying open systems that exchange energy with a surrounding reservoir. In particular, it has been demonstrated that open systems whose spectra exhibit non-Hermitian singularities called exceptional points can demonstrate a host of intriguing effects with potential applications in building new lasers and sensors. At an exceptional point, two or modes become exactly identical. To better understand this, let us consid...

  An image of Neptune from Voyager 2. Credit: NASA/JPL-Caltech Deep inside Neptune and Uranus, temperatures and pressures are extreme enough to produce superionic water—a phase in which oxygen ions crystallize while highly mobile hydrogen ions float through interstitial spaces. Information about superionic water’s phase behavior would help planetary scientists model and understand the ice giants’ evolution, structure, and unusual magnetic fields. Theoretical and computational studies of superionic water’s structure and stability have supplemented scarce experimental data—the phase was observed for the first time in 2019. But those have yielded limited, and sometimes contradictory, results. Now Bingqing Cheng at the University of Cambridge and her collaborators have made predictions about superionic water’s lattice structure at planetary conditions by simulating the material using machine-learning potentials (MLPs) and an artificial neural-network architecture. Molecular-dyn...

  Artist’s illustration of hydrodynamical behavior from an interacting ensemble of quantum spin defects in diamond. Credit: Norman Yao/Berkeley Lab In 1998, researchers including Mark Kubinec of UC Berkeley performed one of the first simple quantum computations using individual molecules. They used pulses of radio waves to flip the spins of two nuclei in a molecule, with each spin's "up" or "down" orientation storing information in the way that a "0" or "1" state stores information in a classical data bit. In those early days of quantum computers, the combined orientation of the two nuclei that is, the molecule's quantum state could only be preserved for brief periods in specially tuned environments. In other words, the system quickly lost its coherence. Control over quantum coherence is the missing step to building scalable quantum computers. Now, researchers are developing new pathways to create and protect quantum coherence. Do...

  A quasar – the most luminous persistent source of light in the universe. Credit: NASA A discovery that provides new insight into how galaxies evolve. At the center of galaxies, like our own Milky Way, lie massive black holes surrounded by spinning gas. Some shine brightly, with a continuous supply of fuel, while others go dormant for millions of years, only to reawaken with a serendipitous influx of gas. It remains largely a mystery how gas flows across the universe to feed these massive black holes. University of Connecticut Assistant Professor of Physics Daniel Anglés-Alcázar, lead author on a paper published recently in The Astrophysical Journal, addresses some of the questions surrounding these massive and enigmatic features of the universe by using new, high-powered simulations. “Supermassive black holes play a key role in galaxy evolution and we are trying to understand how they grow at the centers of galaxies,” says Anglés-Alcázar. “This is very important not just ...

Many contrarians dispute that cosmic inflation occurred. The evidence says otherwise The expanding Universe, full of galaxies and the complex structure we observe today, arose from a smaller, hotter, denser, more uniform state. But even that initial state had its origins, with cosmic inflation as the leading candidate for where that all came from. (Credit: C.-A. Faucher-Giguere, A. Lidz, and L. Hernquist, Science, 2008) KEY TAKEAWAYS Studying the Big Bang tells us how our universe evolved to become this way, but it doesn't immediately reveal why the Big Bang occurred or what might have preceded it. Theoretically and observationally, the evidence for cosmic inflation preceding and setting up the Big Bang is incredibly strong and comprehensive. There are still some new, sensitive things to measure, but the lack of low-hanging fruit doesn't mean the tree is dead. For as long as humans have been around, our innate curiosity has compelled us to ask questions about the universe. Why ...

  STOCKHOLM — The Nobel Prize for physics has been awarded to scientists from Japan, Germany and Italy. Syukuro Manabe, 90, and Klaus Hasselmann, 89, were cited for their work in “the physical modeling of Earth’s climate, quantifying variability and reliably predicting global warming”. The second half of the prize was awarded to Giorgio Parisi, 73, for “the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales.” The panel said Manabe and Hasselmann “laid the foundation of our knowledge of the Earth’s climate and how humanity influences it. Starting in the 1960s, Manabe demonstrated how increases in the amount of carbon dioxide in the atmosphere would increase global temperatures, laying the foundations for current climate models. About a decade later, Hasselmann created a model that linked weather and climate, helping explain why climate models can be reliable despite the seemingly chaotic nature of the weather. He als...

  When these self-propelled particles come together, they can organize and move like schools of fish to perform robotic functions. Credit: Kyle Bishop Lab A challenging frontier in science and engineering is controlling matter outside of thermodynamic equilibrium to build material systems with capabilities that rival those of living organisms. Research on active colloids aims to create micro- and nanoscale "particles" that swim through viscous fluids like primitive microorganisms. When these self-propelled particles come together, they can organize and move like schools of fish to perform robotic functions, such as navigating complex environments and delivering "cargo" to targeted locations. A Columbia Engineering team led by Kyle Bishop, professor of chemical engineering, is at the forefront of studying and designing the dynamics of active colloids powered by chemical reactions or by external magnetic, electric, or acoustic fields. The group is developing colloidal...

While the EU proposes a launcher alliance to support next-generation launch vehicle develop, ESA is working to keep the first Ariane 6 launch on schedule for 2022. Credit: Arianespace WASHINGTON — The European Union is proposing a “launcher alliance” involving companies and governments to develop the next generation of European launch vehicles, although some European startups are skeptical of those plans. In a June 22 speech highlighting the EU’s space programs, including the signing of a Financial Framework Partnership Agreement with the European Space Agency, the EU commissioner responsible for space highlighted the launcher alliance as part of a “ambitious and disruptive space agenda.” “There is no space policy without autonomous access to space,” said Thierry Breton, commissioner for the internal market. “However, it is a segment under massive business and technological changes.” He said the EU had a “fantastic” launch vehicle industry, but that given growing global completion, Eur...