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Category: particle physics – Page 384

Graviton and Massive Symmetric Rank-Two Tensor in String Theory

Abstract: Spin-two particles appear in the spectra of both open and closed string theories. We studied a graviton and massive symmetric rank-two tensor in string theory, both of which carry spin two. A graviton is a massless spin-two particle in closed string theory while a symmetric rank-two tensor is a massive particle with spin two in open string theory. Using Polyakov’s string path integral formulation of string scattering amplitudes, we calculated cubic interactions of both spin-two particles explicitly, including $\ap$-corrections (string corrections). We observed that the cubic interactions of the massive spin-two particle differed from those of the graviton. The massive symmetric rank-two tensor in open string theory becomes massless in the high energy limit where $\ap \rightarrow \infty$ and $\ap$-correction terms, containing higher derivatives, dominate: In this limit the local cubic action of the symmetric rank-two tensor of open string theory coincides with that of the graviton in closed string theory.

From: Taejin Lee [view email].

Scientists discover bizarre ‘worm-like’ aurora stretching halfway across Mars

Nobody can explain why this ‘sinuous discrete aurora’ happened.

While scientists have detected discrete auroras above certain patches of the Red Planet before, never have they seen one on such a “massive scale,” the team said. The solar storm that propelled charged particles into the Martian atmosphere at a faster and more turbulent pace than usual is likely a key factor in this type of long, sinuous aurora, the researchers added.

Solar storm occurrences are predicted to increase over the next several years as the sun approaches its solar maximum — the period of greatest activity in the sun’s 11-year cycle — in 2025. The EMM’s Hope orbiter will continue watching for these newly discovered auroras in the meantime, while scientists dig into archival data collected by NASA and the European Space Agency to hunt for more examples of the snake-like streaks over Mars.

A clock beats inside the heart of every atom

In the pre-industrial age, people only needed to measure years and months to a fair amount of accuracy. The position of the sun in the sky was good enough to break up the day. Timing at the level of fractions of a second was simply not needed.

Eventually, modern industry arose. Fast-moving machines came to dominate human activity, and clocks required hands that could measure seconds. In the current era of digital technology, the timing of electronic circuitry means that millionths or billionths of a second actually matter. None of the high-tech stuff we need, from our phones to our cars, can be controlled or manipulated if we cannot keep close track of it. To make technology work, we need clocks that are faster than the timing of the machines we need to control. For today’s technology, that means we must be able to measure seconds, milliseconds, or even nanoseconds with astonishing accuracy.

Every timekeeping device works via a version of a pendulum. Something must swing back and forth to beat out a basic unit of time. Mechanical clocks used gears and springs. But metal changes shape as it heats or cools, and friction wears down mechanical parts. All of this limits the accuracy of these timekeeping machines. As the speed of human culture climbed higher, it demanded a kind of hyper-fast pendulum that would never wear down.

From seawater to drinking water, with the push of a button

MIT researchers have developed a portable desalination unit, weighing less than 10 kilograms, that can remove particles and salts to generate drinking water.

The suitcase-sized device, which requires less power to operate than a cell phone charger, can also be driven by a small, portable solar panel, which can be purchased online for around $50. It automatically generates drinking that exceeds World Health Organization quality standards. The technology is packaged into a user-friendly device that runs with the push of one button.

Unlike other portable desalination units that require water to pass through filters, this device utilizes to remove particles from drinking water. Eliminating the need for replacement filters greatly reduces the long-term maintenance requirements.

Microrobot collectives display versatile movement patterns

Researchers at the Max Planck Institute for Intelligent Systems (MPI-IS), Cornell University and Shanghai Jiao Tong University have developed collectives of microrobots which can move in any desired formation. The miniature particles are capable of reconfiguring their swarm behavior quickly and robustly. Floating on the surface of water, the versatile microrobotic disks can go round in circles, dance the boogie, bunch up into a clump, spread out like gas or form a straight line like beads on a string.

Each robot is slightly bigger than a hair’s width. They are 3D printed using a polymer and then coated with a thin top layer of cobalt. Thanks to the metal the microrobots become miniature magnets. Meanwhile, wire coils which create a magnetic field when electricity flows through them surround the setup. The magnetic field allows the particles to be precisely steered around a one-centimeter-wide pool of water. When they form a line, for instance, the researchers can move the robots in such a way that they “write” letters in the water. The research project of Gaurav Gardi and Prof. Metin Sitti from MPI-IS, Steven Ceron and Prof. Kirstin Petersen from Cornell University and Prof. Wendong Wang from Shanghai Jiao Tong University titled “Microrobot Collectives with Reconfigurable Morphologies, Behaviors, and Functions” was published in Nature Communications on April 26, 2022.

The Large Hadron Collider Is Back and Ready to Hunt for Dark Matter

Are you ready?

In the control room at CERN (The European Center for Nuclear Research) is a row of empty champagne bottles. Scientists popped open each one to celebrate a successful landmark, like the discovery of the Higgs boson particle, the long-elusive particle that gives all other subatomic particles their mass.

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Chip startups using light instead of wires gaining speed and investments

April 26 (Reuters) — Computers using light rather than electric currents for processing, only years ago seen as research projects, are gaining traction and startups that have solved the engineering challenge of using photons in chips are getting big funding.

In the latest example, Ayar Labs, a startup developing this technology called silicon photonics, said on Tuesday it had raised $130 million from investors including chip giant Nvidia Corp (NVDA.O).

While the transistor-based silicon chip has increased computing power exponentially over past decades as transistors have reached the width of several atoms, shrinking them further is challenging. Not only is it hard to make something so miniscule, but as they get smaller, signals can bleed between them.

After 3 years offline, the Large Hadron Collider immediately sets a world record

The Large Hadron Collider. xenotar/iStock

Whoosh!

After three years of maintenance and upgrades, the Large Hadron Collider — one of the most powerful scientific instruments ever built — has whizzed past its own record. In preparation for its third major run of experiments, the particle accelerator has created the most energetic beams of protons ever made by humans. The particles went racing around the 17-mile (27 km) tunnel near Geneva, Switzerland, with an energy of 6.8 trillion electronvolts (TeV).