Lifeboat Foundation

(Phys.org)—A team of researchers with members from several institutions in the U.S. and one in Germany has proposed the idea of using an extremely small compass needle to build an ultrasensitive magnetometer. In their paper published in Physical Review Letters, the team describes their idea and the possibility of such a device actually being built.

Current magnetometers are very sensitive, able to detect levels of magnetism that are approximately a trillion times less than that of the Earth’s magnetic field. They achieve this feat by taking advantage of the wobble that occurs when an atom is placed in a magnetic field—such magnetometers are made by placing cells of atomic gas in a magnetic field, the wobbles of the atoms are averaged to arrive at a single measurement. In this new effort, the researchers suggest that a new way to measure magnetic fields could be perhaps as much as 1000 times more sensitive.

The idea behind the still theoretically magnetometer comes from the way a compass needle works—instead of wobbling when exposed to a magnetic field, it simply lines up—at least when viewed from a distance. The researchers have shown that such needles do actually wobble like atoms, when they are very small and placed in a very weak magnetic field. They envision a very tiny needle made of cobalt with all of its atoms aligned in a single direction. When the needed is placed in a weak magnetic field, the angular momentum of the rotation of the needle would be a lot smaller than its intrinsic spin angular momentum, which means it would precess, very much like single atoms do. Measuring the precess then would offer a means of measuring the level of magnetism.

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A tool able to generate remote forces would allow us to handle dangerous or fragile materials without contact or occlusions. Acoustic levitation is a suitable technology since it can trap particles in air or water. However, no approach has tried to endow humans with an intertwined way of controlling it. Previously, the acoustic elements were static, had to surround the particles and only translation was possible. Here, we present the basic manoeuvres that can be performed when levitators are attached to our moving hands. A Gauntlet of Levitation and a Sonic Screwdriver are presented with their manoeuvres for capturing, moving, transferring and combining particles. Manoeuvres can be performed manually or assisted by a computer for repeating patterns, stabilization and enhanced accuracy or speed. The presented prototypes still have limited forces but symbolize a milestone in our expectations of future technology.

Theoretical chemists at Princeton University have pioneered a strategy for modeling quantum friction, or how a particle’s environment drags on it, a vexing problem in quantum mechanics since the birth of the field. The study was published in the Journal of Physical Chemistry Letters (“Wigner–Lindblad Equations for Quantum Friction”). “It was truly a most challenging research project in terms of technical details and the need to draw upon new ideas,” said Denys Bondar, a research scholar in the Rabitz lab and corresponding author on the work.

Researchers construct a quantum counterpart of classical friction, a velocity-dependent force acting against the direction of motion. In particular, a translationary invariant Lindblad equation is derived satisfying the appropriate dynamical relations for the coordinate and momentum (i.e., the Ehrenfest equations). Numerical simulations establish that the model approximately equilibrates. (© ACS)

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A new form of light has been discovered by physicists from Trinity College Dublin’s School of Physics and the CRANN Institute, Trinity College, which will impact our understanding of the fundamental nature of light.

One of the measurable characteristics of a beam of light is known as angular momentum, The Spectrum reports. Until now, it was thought that in all forms of light the angular momentum would be a multiple of Planck’s constant (the physical constant that sets the scale of quantum effects).

Now, recent PhD graduate Kyle Ballantine and Professor Paul Eastham, both from Trinity College Dublin’s School of Physics, along with Professor John Donegan from CRANN, have demonstrated a new form of light where the angular momentum of each photon (a particle of visible light) takes only half of this value. This difference, though small, is profound. These results were recently published in the online journal Science Advances.

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Whether these Universes are similar or different to our own, whether they have the same physical laws and properties, whether they have the same fundamental constants, particles and interactions, we do not know.

And at the same time, our very best laws of nature tell us that this is reality: we are a tiny fraction of our observable Universe, which is a tiny bit of the unobservable Universe, which is just one of a tremendous number of Universes in a multiverse that’s constantly generating new ones, and has been for billions of years. And that’s the Multiverse we live in, to the best of our knowledge!

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Abstract: Physicists at the Swiss Nanoscience Institute and the University of Basel have succeeded in measuring the very weak van der Waals forces between individual atoms for the first time. To do this, they fixed individual noble gas atoms within a molecular network and determined the interactions with a single xenon atom that they had positioned at the tip of an atomic force microscope. As expected, the forces varied according to the distance between the two atoms; but, in some cases, the forces were several times larger than theoretically calculated. These findings are reported by the international team of researchers in Nature Communications.

In the late 1990s, astronomers discovered something mysterious pushing galaxies apart faster than gravity pulls them together. It seemed like every little bit of space had some amount of energy that spread it away from every other little bit of space, and that strange pushing came to be known as ‘dark energy’ — dark, because no one knows what it is.

And now a group of physicists have shown that dark energy could probably be explained — as long as we’re willing to give up a fundamental piece of our understanding of light…

Most scientists think that dark energy exists because of what’s known as a cosmological constant — something acting throughout the Universe that tells different bits of space to repel each other. It’s sort of like an anti-gravity force, but it acts everywhere instead of just being between two things with mass and it always acts with the same strength.

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I am told by a TOTEM manager that this is public news and so it can be blogged about — so here I would like to explain a rather cunning plan that the TOTEM and the CMS collaborations have put together to enhance the possibilities of a discovery, and a better characterization, of the particle that everybody hopes is real, the 750 GeV resonance seen in photon pairs data by ATLAS and CMS in their 2015 data.

What is TOTEM, first of all? Well, TOTEM is a collaboration that operates some high-rapidity detectors located around the CMS collision point at the LHC. And before you ask, rapidity is a measurement of how close to the beam a particle is emitted by a collision. Particles emitted orthogonally have rapidity equal to zero; particles traveling at angles increasingly close to the z axis (which we take to be the beam axis at the collision point) have higher positive or negative rapidity (the sign depends on the verse, and is determined by convention). Below is a schematic of the detector.

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Flick a switch on a dark winter day and your office is flooded with bright light, one of many everyday miracles to which we are all usually oblivious.

A physicist would probably describe what is happening in terms of the particle nature of light. An atom or molecule in the fluorescent tube that is in an excited state spontaneously decays to a lower energy state, releasing a particle called a photon. When the photon enters your eye, something similar happens but in reverse. The photon is absorbed by a molecule in the retina and its energy kicks that molecule into an excited state.

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