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Category: physics – Page 104

The surface knows what lies beneath: Physicists show how to detect higher-order topological insulators

Just like a book can’t be judged by its cover, a material can’t always be judged by its surface. But, for an elusive conjectured class of materials, physicists have now shown that the surface previously thought to be “featureless” holds an unmistakable signature that could lead to the first definitive observation.

Higher-order , or HOTIs, have attracted attention for their ability to conduct electricity along one-dimensional lines on their surfaces, but this property is quite difficult to experimentally distinguish from other effects. By instead studying the interiors of these materials from a , a team of physicists has identified a signature that is unique to HOTIs that can determine how light reflects from their surfaces.

As the team reports in the journal Nature Communications, this property could be used to experimentally confirm the existence of such topological states in real materials.

Space Oddity: Uncovering the Origin of the Universe’s Rare Radio Circles

It’s not every day astronomers say, “What is that?” After all, most observed astronomical phenomena are known: stars, planets, black holes and galaxies. But in 2019 the newly completed ASKAP (Australian Square Kilometer Array Pathfinder) telescope picked up something no one had ever seen before: radio wave circles so large they contained entire galaxies in their centers.

As the astrophysics community tried to determine what these circles were, they also wanted to know why the circles were. Now a team led by University of California San Diego Professor of Astronomy and Astrophysics Alison Coil believes they may have found the answer: the circles are shells formed by outflowing galactic winds, possibly from massive exploding stars known as supernovae. Their work is published in Nature.

Coil and her collaborators have been studying massive “starburst” galaxies that can drive these ultra-fast outflowing winds. Starburst galaxies have an exceptionally high rate of star formation. When stars die and explode, they expel gas from the star and its surroundings back into interstellar space. If enough stars explode near each other at the same time, the force of these explosions can push the gas out of the galaxy itself into outflowing winds, which can travel at up to 2,000 kilometers/second.

Galactic Genesis: James Webb Telescope Deciphers Early Universe’s Black Hole Enigma

JWST’s recent observations of two quasars from the universe’s infancy reveal crucial insights into the early relationship between black holes and their galaxies, echoing mass ratios seen in the more recent universe.

New images from the James Webb Space Telescope (JWST) have revealed, for the first time, starlight from two massive galaxies hosting actively growing black holes – quasars – seen less than a billion years after the Big Bang. The black holes have masses close to a billion times that of the Sun, and the host galaxy masses are almost one hundred times larger, a ratio similar to what is found in the more recent universe. A powerful combination of the wide-field survey of the Subaru Telescope and the JWST has paved a new path to study the distant universe, reports a recent study in Nature.

Observations of giant black holes have attracted the attention of astronomers in recent years. The Event Horizon Telescope (EHT) has started to image the “shadow” of black holes at the galaxy centers. The 2020 Novel Prize in Physics was awarded to stellar motion observations at the heart of the Milky Way. While the existence of such giant black holes has become solid, no one knows their origin.

Cosmic Puzzles: The Mystery Behind Universe’s Rare Radio Circles Unveiled

It’s not every day astronomers say, “What is that?” After all, most observed astronomical phenomena are known: stars, planets, black holes, and galaxies. But in 2019 the newly completed ASKAP (Australian Square Kilometer Array Pathfinder) telescope picked up something no one had ever seen before: radio wave circles so large they contained entire galaxies in their centers.

As the astrophysics community tried to determine what these circles were, they also wanted to know why the circles were. Now a team led by University of California San Diego Professor of Astronomy and Astrophysics Alison Coil believes they may have found the answer: the circles are shells formed by outflowing galactic winds, possibly from massive exploding stars known as supernovae. Their work is published in Nature.

Physicists identify overlooked uncertainty in real-world experiments

The equations that describe physical systems often assume that measurable features of the system—temperature or chemical potential, for example—can be known exactly. But the real world is messier than that, and uncertainty is unavoidable. Temperatures fluctuate, instruments malfunction, the environment interferes, and systems evolve over time.

Face to Face with Sun-Eclipsing Proba-3

Through exquisite, millimeter-scale, formation flying, the dual satellites making up ESA’s Proba-3 will accomplish what was previously a space mission impossible: Cast a precisely held shadow from one platform to the other, in the process blocking out the fiery sun to observe its ghostly surrounding atmosphere on a prolonged basis.

Ahead of the Proba-3 pair launching together later this year, the scientists who will make use of Proba-3 observations were able to see the satellites with their own eyes. Members of this team will test hardware developed for the mission during an actual terrestrial solar eclipse over northern America next April.

The two satellites are currently undergoing final integration in the premises of Redwire near Antwerp in Belgium. They were paid a visit by the Proba-3 Science Working Team, a 45-strong group of solar physicists coming from all across Europe and the wider world.

Elon Musk’s Starlink satellites are “leaking” signals

Thousands of satellites have been launched into Earth orbit over the past decade or so, with tens of thousands more planned in coming years. Many of these will be in “mega-constellations” such as Starlink, which aim to cover the entire globe.

These bright, shiny satellites are putting at risk our connection to the cosmos, which has been important to humans for countless millennia and has already been greatly diminished by the growth of cities and artificial lighting. They are also posing a problem for astronomers – and hence for our understanding of the universe.

In new research accepted for publication in Astronomy and Astrophysics Letters, we discovered Starlink satellites are also “leaking” radio signals that interfere with radio astronomy. Even in a “radio quiet zone” in outback Western Australia, we found the satellite emissions were far brighter than any natural source in the sky.

Technique could efficiently solve partial differential equations for numerous applications

In fields such as physics and engineering, partial differential equations (PDEs) are used to model complex physical processes to generate insight into how some of the most complicated physical and natural systems in the world function.

To solve these difficult equations, researchers use high-fidelity numerical solvers, which can be very time consuming and computationally expensive to run. The current simplified alternative, data-driven surrogate models, compute the goal property of a solution to PDEs rather than the whole solution. Those are trained on a set of data that has been generated by the high-fidelity solver, to predict the output of the PDEs for new inputs. This is data-intensive and expensive because complex physical systems require a large number of simulations to generate enough data.

In a new paper, “Physics-enhanced deep surrogates for ,” published in December in Nature Machine Intelligence, a new method is proposed for developing data-driven surrogate models for complex physical systems in such fields as mechanics, optics, thermal transport, fluid dynamics, , and .