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Physics World.

Physicists searching—unsuccessfully—for today’s most favored candidate for dark matter, the axion, have been looking in the wrong place, according to a new supercomputer simulation of how axions were produced shortly after the Big Bang 13.6 billion years ago.

Using new calculational techniques and one of the world’s largest computers, Benjamin Safdi, assistant professor of physics at the University of California, Berkeley; Malte Buschmann, a postdoctoral research associate at Princeton University; and colleagues at MIT and Lawrence Berkeley National Laboratory simulated the era when axions would have been produced, approximately a billionth of a billionth of a billionth of a second after the universe came into existence and after the epoch of cosmic inflation.

The simulation at Berkeley Lab’s National Research Scientific Computing Center (NERSC) found the axion’s mass to be more than twice as big as theorists and experimenters have thought: between 40 and 180 microelectron volts (micro-eV, or μeV), or about one 10-billionth the mass of the electron. There are indications, Safdi said, that the mass is close to 65 μeV. Since physicists began looking for the axion 40 years ago, estimates of the mass have ranged widely, from a few μeV to 500 μeV.

Astronomers find evidence for the tightest-knit supermassive black hole duo observed to date.

Locked in an epic cosmic waltz 9 billion light years away, two supermassive black holes appear to be orbiting around each other every two years. The two giant bodies each have masses that are hundreds of millions of times larger than that of our sun, and the objects are separated by a distance roughly 50 times that which separates our sun and Pluto. When the pair merge in roughly 10,000 years, the titanic collision is expected to shake space and time itself, sending gravitational waves across the universe.

A Caltech-led team of astronomers has discovered evidence for this scenario taking place within a fiercely energetic object known as a quasar. Quasars are active cores of galaxies in which a supermassive black hole is siphoning material from a disk encircling it. In some quasars, the supermassive black hole creates a jet that shoots out at near the speed of light. The quasar observed in the new study, PKS 2131-021, belongs to a subclass of quasars called blazars in which the jet is pointing toward the Earth. Astronomers already knew quasars could possess two orbiting supermassive black holes, but finding direct evidence for this has proved difficult.

Building a better supercomputer is something many tech companies, research outfits, and government agencies have been trying to do over the decades. There’s one physical constraint they’ve been unable to avoid, though: conducting electricity for supercomputing is expensive.

Not in an economic sense—although, yes, in an economic sense, too—but in terms of energy. The more electricity you conduct, the more resistance you create (electricians and physics majors, forgive me), which means more wasted energy in the form of heat and vibration. And you can’t let things get too hot, so you have to expend more energy to cool down your circuits.

Successfully achieving nuclear fusion holds the promise of delivering a limitless, sustainable source of clean energy, but we can only realize this incredible dream if we can master the complex physics taking place inside the reactor.

For decades, scientists have been taking incremental steps towards this goal, but many challenges remain. One of the core obstacles is successfully controlling the unstable and super-heated plasma in the reactor – but a new approach reveals how we can do this.

In a joint effort by EPFL’s Swiss Plasma Center (SPC) and artificial intelligence (AI) research company DeepMind, scientists used a deep reinforcement learning (RL) system to study the nuances of plasma behavior and control inside a fusion tokamak – a donut-shaped device that uses a series of magnetic coils placed around the reactor to control and manipulate the plasma inside it.

The flow of time isn’t as consistent as we might think – gravity slows it down, so clocks on the surface of Earth tick slower than those in space. Now researchers have measured time passing at different speeds across just one millimeter, the smallest distance yet.

The idea that time would be affected by gravity was first proposed by Albert Einstein in 1915, as part of his theory of general relativity. Space and time are inextricably linked, and large masses warp the fabric of spacetime with their immense gravitational influence. This has the effect of making time pass more slowly closer to a large mass like a planet, star, or, in the most extreme example, a black hole. This phenomenon is known as time dilation.

Continue reading “Physicists measure gravitational time warp to within one millimeter” »

Ultraprecise atomic clock poised for new physics discoveries.

New research has shown that future gravitational wave detections from space will be capable of finding new fundamental fields and potentially shed new light on unexplained aspects of the Universe.

Professor Thomas Sotiriou from the University of Nottingham’s Centre of Gravity and Andrea Maselli, researcher at GSSI and INFN associate, together with researchers from SISSA, and La Sapienza of Rome, showed the unprecedented accuracy with which gravitational wave observations by the space interferometer LISA (Laser Interferometer Space Antenna), will be able to detect new fundamental fields. The research has been published in Nature Astronomy.

In this new study researchers suggest that LISA, the space-based gravitational-wave (GW) detector which is expected to be launched by ESA in 2037 will open up new possibilities for the exploration of the Universe.

Most energy-producing technologies used today are unsustainable, as they cause significant damage to our planet’s natural environment. In recent years, scientists worldwide have thus been trying to devise alternative energy solutions that take advantage of abundant and natural resources.

In addition to solar energy, wind energy and seawater energy solutions, some physicists and engineers have been exploring the possibility of sourcing energy from nuclear fusion reactions. This is the process through which two atomic nuclei combine to form a heavier nucleus and an energetic neutron.

Two research teams working at the Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF) demonstrated new approaches to increase nuclear energy production via a laser-driven fusion reaction. Their findings, published in recent Nature and Nature Physics papers, open new exciting possibilities for one day using self-heating plasmas as sustainable energy sources.