A joint research team from Japan has observed “heavy fermions,” electrons with dramatically enhanced mass, exhibiting quantum entanglement governed by the Planckian time – the fundamental unit of time in quantum mechanics. This discovery opens up exciting possibilities for harnessing this phenomenon in solid-state materials to develop a new type of quantum computer.
Two recent studies by Professor Stefano Profumo at the University of California, Santa Cruz, propose theories that attempt to answer one of the most fundamental open questions in modern physics: What is the particle nature of dark matter?
Science has produced overwhelming evidence that the mysterious substance, which accounts for 80% of all matter in the universe, exists. Dark matter’s presence explains what binds galaxies together and makes them rotate. Findings such as the large-scale structure of the universe and measurements of the cosmic microwave background also prove that something as-yet undetermined permeates all that darkness.
What remains unknown are the origins of dark matter, and hence, what are its particle properties? Those weighty questions primarily fall to theoretical physicists like Profumo. And in two recent papers, he approaches those questions from different directions, but both centered on the idea that dark matter might have emerged naturally from conditions in the very early universe—rather than dark matter being an exotic new particle that interacts with ordinary matter in some detectable way.
In the everyday world that humans experience, objects behave in a predictable way, explained by classical physics. One of the important aspects of classical physics is that nothing travels faster than the speed of light. Even information is subject to this rule. However, in the 1930s, scientists discovered that very small particles abide by some very different rules. One of the more mind-boggling behaviors exhibited by these particles was quantum entanglement—which Albert Einstein termed “spooky action at a distance.”
In quantum entanglement, two particles can become entangled—meaning their properties are correlated with each other and measuring these properties will always give you opposite results (i.e., if one is oriented up, the other must be down). The strange part is that you still get correlated measurements instantaneously, even if these particles are very far away from each other.
If information cannot travel faster than the speed of light, then there should not be a way for one particle to immediately know the state of the other. This “spooky” quantum property is referred to as “nonlocality”—exhibiting effects that should not be possible at large distances in classical mechanics.
Incorporated into every aspect of everyday life, the neutron is a fundamental particle of nature. Now, a research collaboration led by Los Alamos National Laboratory has improved the precision of free neutron lifetime measurements. The team’s results highlight the success of the UCNTau experiment’s design and previews the effectiveness of new techniques and approaches that the team is incorporating into the next generation of the experiment.
“The precise lifetime of free neutrons is at the center of still-contested physics questions,” said Steven Clayton, physicist at Los Alamos. “Understanding the neutron lifetime can be used to test the nature of the weak force, one of the fundamental forces of the universe, and can also help search for physics beyond the Standard Model.
Our results here validate the UCNtau experimental approach and point the way toward design improvements that will further enhance our understanding of the physics involved.
What if particles don’t slow down in a crowd, but move faster? Physicists from Leiden worked together and discovered a new state of matter, where particles pass on energy through collisions and create more movement when packed closely together.
We all know crowds of people, or cars in a traffic jam—when it gets too crowded, all you can do is stand still. Until now, scientists have mainly studied cases of large groups just like this, which slow down when they get too close to each other.
But what if the opposite happens? What if particles could start moving more when packed together? That question hadn’t been studied much—until now. Physicists Marine Le Blay, Joshua Saldi and Alexandre Morin from Leiden University do research in the field of active matter physics—they observe and analyze the collective behaviors that emerge when large groups of particles are packed together.
Chinese scientists develop self-cleaning glass that uses electric fields to remove dust.
The thin, transparent glass embedded with electric-field-driven electrodes can clean itself in seconds, erasing up to 98% of dust particles.
Trying to capture antineutrinos at low energy has just become a lot easier.
Carl David Anderson was born in New York City, the son of Swedish immigrants. He studied physics and engineering at Caltech (B.S., 1927; Ph. D., 1930). Under the supervision of Robert Millikan, He began investigations into cosmic rays during the course of which he encountered unexpected particle tracks in his (modern versions now commonly referred to as an Anderson) cloud chamber photographs that he correctly interpreted as having been created by a particle with the same mass as the electron, but with opposite electrical charge. This discovery, announced in 1932 and later confirmed by others, validated Paul Dirac’s theoretical prediction of the existence of the positron. Anderson first detected the particles in cosmic rays. He then produced more conclusive proof by shooting gamma rays produced by the natural radioactive nuclide ThC’’ (208 Tl) [ 2 ] into other materials, resulting in the creation of positron-electron pairs. For this work, Anderson shared the 1936 Nobel Prize in Physics with Victor Hess. [ 3 ] Fifty years later, Anderson acknowledged that his discovery was inspired by the work of his Caltech classmate Chung-Yao Chao, whose research formed the foundation from which much of Anderson’s work developed but was not credited at the time. [ 4 ]
Also in 1936, Anderson and his first graduate student, Seth Neddermeyer, discovered a muon (or ‘mu-meson’, as it was known for many years), a subatomic particle 207 times more massive than the electron, but with the same negative electric charge and spin 1/2 as the electron, again in cosmic rays. Anderson and Neddermeyer at first believed that they had seen a pion, a particle which Hideki Yukawa had postulated in his theory of the strong interaction. When it became clear that what Anderson had seen was not the pion, the physicist I. I. Rabi, puzzled as to how the unexpected discovery could fit into any logical scheme of particle physics, quizzically asked “Who ordered that?” (sometimes the story goes that he was dining with colleagues at a Chinese restaurant at the time). The muon was the first of a long list of subatomic particles whose discovery initially baffled theoreticians who could not make the confusing “zoo” fit into some tidy conceptual scheme.
