Physicists finds evidence from just after the Big Bang that supports the controversial holographic universe theory.
The idea of time crystals sparked much controversy and skepticism among physicists, who doubted such a phenomenon could ever be observed.
These ‘photonic time crystals’ can amplify microwave frequencies, but the team that developed them is confident they could work on longer wavelengths too.
The Event Horizon Telescope collaboration, including scientists from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has recently resolved the jet base of an evolving jet of plasma at ultra-high angular resolution.
The international team of scientists used the Earth-size telescope to probe the magnetic structure in the nucleus of the radio galaxy 3C 84 (Perseus A), one of the closest active supermassive black holes in our cosmic neighborhood.
These novel results provide new insight into how jets are launched, revealing that in this cosmic tug of war, the magnetic fields overpower gravity. The study is published in the journal Astronomy & Astrophysics.
A group of astrophysicists led by Mireia Montes, a researcher at the Instituto de Astrofísica de Canarias (IAC), has discovered the largest and most diffuse galaxy recorded until now. The study has been published in the journal Astronomy & Astrophysics, and has used data taken with the Gran Telescopio Canarias (GTC) and the Green Bank Radiotelescope (GBT).
Nube is an almost invisible dwarf galaxy discovered by an international research team led by the Instituto de Astrofísica de Canarias (IAC) in collaboration with the University of La Laguna (ULL) and other institutions.
The name was suggested by the 5-year-old daughter of one of the researchers in the group, and is due to the diffuse appearance of the object. Its surface brightness is so faint that it had passed unnoticed in the various previous surveys of this part of the sky, as if it were some kind of ghost. This is because its stars are so spread out in such a large volume that “Nube” (the Spanish for “Cloud”) was almost undetectable.
MIT physicists have metaphorically turned graphite, or pencil lead, into gold by isolating five ultrathin flakes stacked in a specific order. The resulting material can then be tuned to exhibit three important properties never before seen in natural graphite.
“It is kind of like one-stop shopping,” says Long Ju, an assistant professor in the Department of Physics and leader of the work, which is reported in the Oct. 5 issue of Nature Nanotechnology. “Nature has plenty of surprises. In this case, we never realized that all of these interesting things are embedded in graphite.”
Further, he says, “It is very rare material to find materials that can host this many properties.”
For the past year and a half, the James Webb Space Telescope has delivered astonishing images of distant galaxies formed not long after the Big Bang, giving scientists their first glimpses of the infant universe. Now, a group of astrophysicists has upped the ante: Find the tiniest, brightest galaxies near the beginning of time itself, or scientists will have to totally rethink their theories about dark matter.
The team, led by UCLA astrophysicists, ran simulations that track the formation of small galaxies after the Big Bang and included, for the first time, previously neglected interactions between gas and dark matter. They found that the galaxies created are very tiny, much brighter, and form more quickly than they do in typical simulations that don’‘t take these interactions into account, instead revealing much fainter galaxies.
Small galaxies, also called dwarf galaxies, are present throughout the universe, and are often thought to represent the earliest type of galaxy. Small galaxies are thus especially interesting to scientists studying the origins of the universe. But the small galaxies they find don’t always match what they think they should find. Those closest to the Milky Way spin quicker or are not as dense as in simulations, indicating that the models might have omitted something, such as these gas-dark matter interactions.
Existence of an axial (poloidal) component of magnetic field in the dense plasma focus has been inferred using multiple diagnostics in many laboratories since 1979. It has not received much attention because its origin as well as role in plasma focus physics was unclear till recently. Recent discovery of long-lasting neutron emission perpendicular to the axis in PF-1000 and neutron fluence ratio (end/side) less than unity in Gemini shows that azimuthally accelerated and radially confined deuterons play an observable role in fusion reactions. A spontaneously generated poloidal magnetic field can provide both the azimuthal electric field necessary for acceleration and radial confinement of the ions being accelerated in the acceleration zone. A comprehensive survey of plasma focus research also confirms the role of spontaneously self-organized plasma objects in the fusion reaction process where their three-dimensional magnetic field structure provides a mechanism for accelerating and trapping ions making them repeatedly pass through a dense plasma target. With emerging appreciation of the likely role of the axial magnetic field in plasma focus neutron emission, it becomes imperative to consider models for its origin. This Letter proposes a partial theory of growth of the axial (poloidal) magnetic field via a simple dynamo, with the geomagnetic field as the seed, which converts the kinetic energy of the plasma into energy of the poloidal magnetic field. This theory leads to an experimentally testable proposition.
Simulating KH-, RT-, or RM-driven mixing using direct numerical simulations (DNS) can be prohibitively expensive because all the spatial and temporal scales have to be resolved, making approaches such as Reynolds-averaged Navier–Stokes (RANS) often the more favorable engineering option for applications like ICF. To this day, no DNS has been performed for ICF even on the largest supercomputers, as the resolution requirements are too stringent.8 However, RANS approaches also face their own challenges: RANS is based on the Reynolds decomposition of a flow where mean quantities are intended to represent an average over an ensemble of realizations, which is often replaced by a spatial average due to the scarcity of ensemble datasets. Replacing ensemble averages by space averages may be appropriate for flows that are in homogenous-, isotropic-, and fully developed turbulent states in which spatial, temporal, and ensemble averaging are often equivalent. However, most HED hydrodynamic experiments involve transitional periods in which the flow is neither homogeneous nor isotropic nor fully developed but may contain large-scale unsteady dynamics; thus, the equivalency of averaging can no longer be assumed. Yet, RANS models often still require to be initialized in such states of turbulence, and knowing how and when to initialize them in a transitional state is, therefore, challenging and is still poorly understood.
The goal of this paper is to develop a strategy allowing the initialization of a RANS model to describe an unsteady transitional RM-induced flow. We seek to examine how ensemble-averaged quantities evolve during the transition to turbulence based on some of the first ensemble experiments repeated under HED conditions. Our strategy involves using 3D high-resolution implicit large eddy simulations (ILES) to supplement the experiments and both initialize and validate the RANS model. We use the Besnard–Harlow–Rauenzahn (BHR) model,9–12 specifically designed to predict variable-density turbulent physics involved in flows like RM. Previous studies have considered different ways of initializing the BHR model.
Reliably guiding and capturing optical waves is central to the functioning of various contemporary technologies, including communication and information processing systems. The most conventional approach to guide light waves leverages the total internal reflection of optical fibers and other similar structures, yet recently physicists have been exploring the potential of techniques based on other physical mechanisms.
Researchers at University of Southern California recently devised a highly innovative approach for trapping light. This method, introduced in Nature Physics, exploits the exotic properties of Lagrange points, the same equilibrium points that govern the orbits of primordial celestial bodies, such as so-called Trojan asteroids in the sun-Jupiter system.
“The discovery of Lagrange points, which happens to be pivotal in this research, can be traced back to the early work of Leonhard Euler and Joseph-Louis Lagrange, which found that at these locations, the gravitational attraction exerted by two large bodies can be precisely counterbalanced by centrifugal forces,” Mercedeh Khajavikhan and Demetrios N. Christodoulides, co-authors of the paper, told Phys.org.
