A brief explanation of how superfluid dark matter can combine fluid dark matter and modified gravity.
For galaxy clusters and for the cosmic microwave background, dark matter matter is the better explanation. But to explain galactic rotation curves and other properties of galaxies, modified gravity is the better explanation.
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Astrophysicists hope a map created by the Dark Energy Spectroscopic Instrument will help answer questions about the expansion of the universe.
Continue reading “Largest 3D map of the universe contains 8 million galaxies” »
New James Webb Space Telescope observations may have done with one of the longest-standing tensions in cosmology.
For almost a decade, astronomers have been struggling with a nagging mismatch between two different ways of determining the Hubble constant — a measure of the current expansion rate of the universe. This mismatch, known as the Hubble tension, has led to claims that new physics might be needed to solve the issue. (Read about the “constant controversy” in the June 2019 issue of Sky & Telescope.)
But a detailed analysis of a new set of James Webb Space Telescope (JWST) observations now suggests that the problem may not exist. “As Carl Sagan said, extraordinary claims require extraordinary evidence,” says Wendy Freedman (University of Chicago), “and I don’t see extraordinary evidence.”
Researchers from LMU, the ORIGINS Excellence Cluster, the Max Planck Institute for Extraterrestrial Physics (MPE), and the ORIGINS Data Science Lab (ODSL) have made an important breakthrough in the analysis of exoplanet atmospheres.
Ten years ago, researchers succeeded in suppressing sound wave propagation in the backward direction; however, this also attenuated the waves traveling forwards.
A team of researchers at ETH Zurich led by Nicolas Noiray, professor for Combustion, Acoustics and Flow Physics, in collaboration with Romain Fleury at EPFL, has now developed a method for preventing sound waves from traveling backward without deteriorating their propagation in the forward direction.
In the future, this method, which has recently been published in Nature Communications, could also be applied to electromagnetic waves.
Building a nuclear fusion reactor capable of providing green energy for homes and industry is the goal of many physicists around the world, but many roadblocks stand between our present and this green energy future. While some of those hurdles have been overcome, building robust materials capable of surviving the hellish conditions inside tokamaks is the next frontier.
As engineers construct next-generation fusion reactors, like the International Thermonuclear Experimental Reactor (ITER) in southern France, labs around the world are working on creating exotic materials capable of containing super-hot plasma while also generating electricity. One of those labs is MIT Energy Initiative (MITEI), which is dedicated to finding ways to make future reactors more robust and reliable.
Researchers at the Department of Instrumentation and Applied Physics (IAP), Indian Institute of Science (IISc) and collaborators have designed a new supercapacitor that can be charged by light shining on it. Such supercapacitors can be used in various devices, including streetlights and self-powered electronic devices such as sensors.
Capacitors are electrostatic devices that store energy as charges on two metal plates called electrodes. Supercapacitors are upgraded versions of capacitors—they exploit electrochemical phenomena to store more energy, explains Abha Misra, Professor at IAP and corresponding author of the study published in the Journal of Materials Chemistry A.
The electrodes of the new supercapacitor were made of zinc oxide (ZnO) nanorods grown directly on fluorine-doped tin oxide (FTO), which is transparent. It was synthesized by Pankaj Singh Chauhan, first author and CV Raman postdoctoral fellow in Misra’s group at IISc.
In the case of NiPS3, the researchers observed an intermediate symmetry breaking which leads to a vestigial order. Just as the term “vestigial” refers to the retention of certain traits during the process of evolution, the vestigial order here can also be viewed as the retention during the process of symmetry breaking.
This happens when the primary magnetic long-range order state melts or breaks down into a simpler form, in the NiPS3 case, a 2D vestigial order state (known as Z3 Potts-nematicity), as the material is thinned. Unlike conventional symmetry breaking, which involves the breaking of all symmetries, vestigial order only involves the breaking of some symmetries.
While there are numerous examples from a theoretical standpoint, experimental realizations of vestigial order have remained challenging. However, the investigation of this 2D magnetic material has shed the first light on this issue, demonstrating that such a phenomenon can be observed through dimension crossover.
A better understanding of the inner workings of neutron stars will lead to a greater knowledge of the dynamics that underpin the workings of the universe and also could help drive future technology, said the University of Illinois Urbana-Champaign physics professor Nicolas Yunes. A new study led by Yunes details how new insights into how dissipative tidal forces within double—or binary—neutron star systems will inform our understanding of the universe.
A collaborative study by the University of Cologne revealed that magnetic excitations in BaCO2V2O8 crystals involve unusual repulsively bound states, a significant discovery made by irradiating the crystals with terahertz waves.
A team of solid-state physicists from the University of Cologne, along with international collaborators, studied BaCO2V2O8 crystals in a laboratory in Cologne. Their research revealed that the magnetic elementary excitations in the crystals are influenced by both attractive and repulsive interactions.
However, this results in a lower stability, making the observation of such repulsively bound states all the more surprising. The results of the study were recently published in Nature.
