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The universe is almost devoid of antimatter, and physicists haven’t yet figured out why. Discovering any slight difference between the behaviour of antimatter and matter in Earth’s gravitational field could shed light on this question. Positronium atoms, which consist of an electron and a positron, are one type of antimatter atoms being considered to test whether antimatter falls at the same rate as matter in Earth’s gravitational field. But they are short-lived, lasting a mere 142 nanoseconds – too little to perform an antimatter gravity experiment. Researchers are therefore actively seeking tricks to make sources of positronium atoms that live longer. In a paper published today in the journal Physical Review A, the AEgIS collaboration at CERN describes a new way of making long-lived positronium.

To be useful for antimatter gravity experiments, a source of positronium atoms needs to produce long-lived atoms in large numbers, and with known velocities that can be controlled and are unaffected by disturbances such as electric and magnetic fields. The new AEgIS source ticks all of these boxes, producing some 80 000 positronium atoms per minute that last 1140 nanoseconds each and have a known velocity (between 70 and 120 kilometres per second) that can be controlled with a high precision (10 kilometres per second).

Continue reading “Making long-lived positronium atoms for antimatter gravity experiments” »

Since the end of the 19th century, physicists have known that the transfer of energy from one body to another is associated with entropy. It quickly became clear that this quantity is of fundamental importance, and so began its triumphant rise as a useful theoretical quantity in physics, chemistry and engineering. However, it is often very difficult to measure. Professor Dietmar Block and Frank Wieben of Kiel University (CAU) have now succeeded in measuring entropy in complex plasmas, as they reported recently in the renowned scientific journal Physical Review Letters. In a system of charged microparticles within this ionized gas, the researchers were able to measure all positions and velocities of the particles simultaneously. In this way, they were able to determine the entropy, as it was already described theoretically by the physicist Ludwig Boltzmann around 1880.

Surprising thermodynamic equilibrium in plasma

“With our experiments, we were able to prove that in the important model system of complex plasma, the thermodynamic fundamentals are fulfilled. What is surprising is that this applies to microparticles in a plasma, which is far away from thermodynamic equilibrium,” explains Ph.D. student Frank Wieben. In his experiments, he is able to adjust the thermal motion of the microparticles by means of a laser beam. Using video microscopy, he can observe the dynamic behaviour of the particles in real time, and determine the entropy from the information collected.

Teams have looked for a “fifth force” in the universe within the Earth’s mantle, ultra-vacuum chambers, and in hypothetical particles such as “X17.” Finding it could help explain mysteries around dark matter and dark energy.

This could usher in higgs exotic physics computing that is beyond even quantum computers.

When a continuous symmetry of a physical system is spontaneously broken, two types of collective modes typically emerge: the amplitude and phase modes of the order-parameter fluctuation. For superconductors, the amplitude mode is recently referred to as the ‘’Higgs mode’’ as it is a condensed-matter analogue of a Higgs boson in particle physics. Higgs mode is a scalar excitation of the order parameter, distinct from charge or spin fluctuations, and thus does not couple to electromagnetic fields linearly. This is why the Higgs mode in superconductors has evaded experimental observations over a half century after the initial theoretical prediction, except for a charge-density-wave coexisting system.

Circa 2018

Higgs and Goldstone modes are possible collective modes of an order parameter on spontaneously breaking a continuous symmetry. Whereas the low-energy Goldstone (phase) mode is always stable, additional symmetries are required to prevent the Higgs (amplitude) mode from rapidly decaying into low-energy excitations. In high-energy physics, where the Higgs boson¹ has been found after a decades-long search, the stability is ensured by Lorentz invariance. In the realm of condensed-matter physics, particle–hole symmetry can play this role² and a Higgs mode has been observed in weakly interacting superconductors^3,4,5. However, whether the Higgs mode is also stable for strongly correlated superconductors in which particle–hole symmetry is not precisely fulfilled or whether this mode becomes overdamped has been the subject of numerous discussions^{6,7,8,9,10,11}. Experimental evidence is still lacking, in particular owing to the difficulty of exciting the Higgs mode directly. Here, we observe the Higgs mode in a strongly interacting superfluid Fermi gas. By inducing a periodic modulation of the amplitude of the superconducting order parameter Δ, we observe an excitation resonance at the frequency 2Δ/h. For strong coupling, the peak width broadens and eventually the mode disappears when the Cooper pairs turn into tightly bound dimers signalling the eventual instability of the Higgs mode.

If you use a vacuum-insulated thermos to help keep your coffee hot, you may know it’s a good insulator because heat energy has a hard time moving through empty space. Vibrations of atoms or molecules, which carry thermal energy, simply can’t travel if there are no atoms or molecules around.

But a new study by researchers at the University of California, Berkeley, shows how the weirdness of quantum mechanics can turn even this basic tenet of classical physics on its head.

The study, appearing this week in the journal Nature, shows that heat energy can leap across a few hundred nanometers of a complete vacuum, thanks to a quantum mechanical phenomenon called the Casimir interaction.

No one has ever seen an active asteroid up close like this.

“Among Bennu’s many surprises, the particle ejections sparked our curiosity, and we’ve spent the last several months investigating this mystery,” Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson, said in a statement. “This is a great opportunity to expand our knowledge of how asteroids behave.”

The researchers are trying to figure out what is causing these “ejection events.”

Continue reading “NASA Baffled: Asteroid Bennu Keeps Spitting Out Small Rocks” »

The Higgs boson is an elementary particle in the Standard Model of particle physics, produced by the quantum excitation of the Higgs field,^[8][9] one of the fields in particle physics theory.^[9] It is named after physicist Peter Higgs, who in 1964, along with five other scientists, proposed the Higgs mechanism to explain why particles have mass. This mechanism implies the existence of the Higgs boson. The boson’s existence was confirmed in 2012 by the ATLAS and CMS collaborations based on collisions in the LHC at CERN.

On December 10, 2013, two of the physicists, Peter Higgs and François Englert, were awarded the Nobel Prize in Physics for their theoretical predictions. Although Higgs’s name has come to be associated with this theory (the Higgs mechanism), several researchers between about 1960 and 1972 independently developed different parts of it.

In mainstream media the Higgs boson has often been called the “God particle”, from a 1993 book on the topic,^[10] although the nickname is strongly disliked by many physicists, including Higgs himself, who regard it as sensationalism.^[11][12].

Quantum field theory doesn’t get much coverage in popular science and if you open any textbook on the subject you’ll see why. It looks like an unholy crossbreed between quantum physics in a bad mood and every button you never push on a calculator. The idea of summarising it in 1,500 words or less for this article sounded daunting at first (it took a whole chapter to cover it in my recent book) but then again if I really did have to present it to a jury of aliens I wouldn’t have a choice.

Therefore, your honour, I request that you give me five minutes of your intergalactic attention. My presentation may not feature Jason Statham roundhouse kicking a shark in the eyeball, but I am going to try and justify the continued existence of the human race. Here goes…

Continue reading “Quantum field theory: ‘An unholy crossbreed between quantum physics in a bad mood and every button you never push on a calculator’” »