A hidden link between two seemingly unrelated particle collision outcomes shows a mysterious web of mathematical connections between disparate theories.
Category: particle physics – Page 278
In Einstein’s theory of general relativity, gravity arises when a massive object distorts the fabric of spacetime the way a ball sinks into a piece of stretched cloth. Solving Einstein’s equations by using quantities that apply across all space and time coordinates could enable physicists to eventually find their “white whale”: a quantum theory of gravity.
In a new article in The European Physical Journal H 0, Donald Salisbury from Austin College in Sherman, USA, explains how Peter Bergmann and Arthur Komar first proposed a way to get one step closer to this goal by using Hamilton-Jacobi techniques. These arose in the study of particle motion in order to obtain the complete set of solutions from a single function of particle position and constants of the motion.
Three of the four fundamental forces —strong, weak, and electromagnetic—hold under both the ordinary world of our everyday experience, modeled by classical physics, and the spooky world of quantum physics. Problems arise, though, when trying to apply to the fourth force, gravity, to the quantum world. In the 1960s and 1970s, Peter Bergmann of Syracuse University, New York and his associates recognized that in order to someday reconcile Einstein’s theory of general relativity with the quantum world, they needed to find quantities for determining events in space and time that applied across all frames of reference. They succeeded in doing this by using the Hamilton-Jacobi techniques.
A team of researchers from Nanjing University of Posts and Telecommunications and the Chinese Academy of Sciences in China and Nanyang Technological University and the Agency for Science Technology and Research in Singapore developed an artificial neuron that is able to communicate using the neurotransmitter dopamine. They published their creation and expected uses for it in the journal Nature Electronics.
As the researchers note, most machine-brain interfaces rely on electrical signals as a communications medium, and those signals are generally one-way. Electrical signals generated by the brain are read and interpreted; signals are not sent to the brain. In this new effort, the researchers have taken a step toward making a brain-machine interface that can communicate in both directions, and it is not based on electrical signals. Instead, it is chemically mediated.
The work involved building an artificial neuron that could both detect the presence of dopamine and also produce dopamine as a response mechanism. The neuron is made of graphene (a single sheet of carbon atoms) and a carbon nanotube electrode (a single sheet of carbon atoms rolled up into a tube). They then added a sensor capable of detecting the presence of dopamine and a device called a memristor that is capable of releasing dopamine using a heat-activated hydrogel, attached to another part of their artificial neuron.
Simulations of a quantum computer made of six rubidium atoms suggest it could run a simple brain-inspired algorithm that can learn to remember and make simple decisions.
A new method for shaping matter into complex shapes, with the use of ‘twisted’ light, has been demonstrated in research at the University of Strathclyde.
When atoms are cooled to temperatures close to absolute zero (−273 degrees C), they stop behaving like particles and start to behave like waves.
Atoms in this condition, which are known as Bose–Einstein condensates (BECs), are useful for purposes such as realization of atom lasers, slow light, quantum simulations for understanding the complex behavior of materials like superconductors and superfluids, and the precision measurement technique of atom interferometry.
If we could harness fusion to generate electricity, it would be one of the most efficient and least polluting sources of energy possible.
A major breakthrough in nuclear fusion has been confirmed a year after it was achieved at a laboratory in California.
Researchers at Lawrence Livermore National Laboratory’s (LLNL’s) National Ignition Facility (NIF) recorded the first case of ignition on August 8, 2021, the results of which have now been published in three peer-reviewed papers.
Nuclear fusion is the process that powers the Sun and other stars: heavy hydrogen atoms collide with enough force that they fuse together to form a helium atom, releasing large amounts of energy as a by-product. Once the hydrogen plasma “ignites”, the fusion reaction becomes self-sustaining, with the fusions themselves producing enough power to maintain the temperature without external heating.
A research team succeeded in executing the world’s fastest two-qubit gate (a fundamental arithmetic element essential for quantum computing) using a completely new method of manipulating, with an ultrafast laser, micrometer-spaced atoms cooled to absolute zero temperature. For the past two decade.
“ data-gt-translate-attributes=’[{“attribute”:” data-cmtooltip”, “format”:” html”}]’quantum computing ) using a completely new method of manipulating, with an ultrafast laser, micrometer-spaced atoms cooled to absolute zero.
Absolute zero is the theoretical lowest temperature on the thermodynamic temperature scale. At this temperature, all atoms of an object are at rest and the object does not emit or absorb energy. The internationally agreed-upon value for this temperature is −273.15 °C (−459.67 °F; 0.00 K).
Astronomers have long sought the launch sites for some of the highest-energy protons in our galaxy. Now a study using 12 years of data from NASA’s Fermi Gamma-ray Space Telescope confirms that one supernova remnant is just such a place.
Fermi has shown that the shock waves of exploded stars boost particles to speeds comparable to that of light. Called cosmic rays, these particles mostly take the form of protons, but can include atomic nuclei and electrons. Because they all carry an electric charge, their paths become scrambled as they whisk through our galaxy’s magnetic field. Since we can no longer tell which direction they originated from, this masks their birthplace. But when these particles collide with interstellar gas near the supernova remnant, they produce a telltale glow in gamma rays—the highest-energy light there is.
“Theorists think the highest-energy cosmic ray protons in the Milky Way reach a million billion electron volts, or PeV energies,” said Ke Fang, an assistant professor of physics at the University of Wisconsin, Madison. “The precise nature of their sources, which we call PeVatrons, has been difficult to pin down.”
The space between the planets in our solar system is filled with a wispy sea of charged particles that flow out from the Sun’s atmosphere. This particle population is augmented by cosmic rays — speedy protons and atomic nuclei accelerated in extreme environments across the universe — which ebb and flow against the 11-year solar activity cycle. This undulating particle background is punctuated by bursts of high-energy particles from the Sun, which can be unleashed suddenly in violent solar storms.
Spacecraft that venture out from the protection of Earth’s magnetic field must navigate this ocean of particles and weather solar storms. And if we someday wish to send astronauts to other planets, we’ll need to know how high-energy solar particles, which pose a risk to the health of astronauts and electronic systems alike, travel through the solar system.
In a new publication, a team led by Shuai Fu (Macau University of Science and Technology), Zheyi Ding (China University of Geosciences), and Yongjie Zhang (Chinese Academy of Sciences) studied the high-energy solar particles produced in an event in November 2020, when the Sun emitted a solar flare and a massive explosion of solar plasma called a coronal mass ejection.
For decades, if you asked a fusion scientist to picture a fusion reactor, they’d probably tell you about a tokamak. It’s a chamber about the size of a large room, shaped like a hollow doughnut. Physicists fill its insides with a not-so-tasty jam of superheated plasma. Then they surround it with magnets in the hopes of crushing atoms together to create energy, just as the sun does.
But experts think you can make tokamaks in other shapes. Some believe that making tokamaks smaller and leaner could make them better at handling plasma. If the fusion scientists proposing it are right, then it could be a long-awaited upgrade for nuclear energy. Thanks to recent research and a newly proposed reactor project, the field is seriously thinking about generating electricity with a “spherical tokamak.”
“The indication from experiments up to now is that [spherical tokamaks] may, pound for pound, confine plasmas better and therefore make better fusion reactors,” says Steven Cowley, director of Princeton Plasma Physics Laboratory.