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Category: particle physics – Page 550

The most popular contender over the past few decades has been string theory, and the related concepts of superstring theory and M-theory, in which particles are considered as tiny units of one-dimensional string. However, a lesser-known theory has also gained traction; loop quantum gravity (LQG), which attempts to solve the quantum gravity problem by focusing on the very fabric of spacetime, rather than the particles themselves.

In “Quantum Space,” the popular-science writer Jim Baggott lays out the basic principles of LQG for science enthusiasts. The book looks at how loop quantum gravity has emerged by following the work of two of its leading proponents, Carlo Rovelli and Lee Smolin, and assesses where the theory is now, and where it might be going.

Although the concepts are — not surprisingly — mind-boggling, Baggott asks deep questions about the nature of the universe, what space is actually composed of, and the existence of time itself. (The book covers a lot of challenging material, however, and some prior reading may help readers find their way.)

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When a particle is completely isolated from its environment, the laws of quantum physics start to play a crucial role. One important requirement to see quantum effects is to remove all thermal energy from the particle motion, i.e. to cool it as close as possible to absolute zero temperature. Researchers at the University of Vienna, the Austrian Academy of Sciences and the Massachusetts Institute of Technology (MIT) are now one step closer to reaching this goal by demonstrating a new method for cooling levitated nanoparticles. They now publish their results in the renowned journal Physical Review Letters.

Tightly focused can act as optical “tweezers” to trap and manipulate tiny objects, from glass to living cells. The development of this method has earned Arthur Ashkin the last year’s Nobel prize in physics. While most experiments thus far have been carried out in air or liquid, there is an increasing interest for using to trap objects in ultra-high vacuum: such isolated particles not only exhibit unprecedented sensing performance, but can also be used to study fundamental processes of nanoscopic heat engines, or phenomena involving large masses.

A key element in these research efforts is to obtain full control over the particle motion, ideally in a regime where the laws of quantum physics dominate its behavior. Previous attempts to achieve this, have either modulated the optical tweezer itself, or immersed the particle into additional light fields between highly reflecting mirror configurations, i.e. optical cavities.

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Everything you see around you is made up of elementary particles called quarks and leptons, which can combine to form bigger particles such as protons or atoms.

But that doesn’t make them boring – these subatomic particles can also combine in exotic ways we’ve never spotted.

Now CERN’s LHCb collaboration has announced the discovery of a clutch of new particles dubbed “pentaquarks”. The results can help unveil many mysteries of the theory of quarks, a key part of the standard model of particle physics.

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If you throw a ball at a wall, it’s going to bounce back at you – that’s classical physics at work. But of course, the world of quantum physics is much spookier, so if you did the same with a particle, there’s a chance that it will suddenly appear on the other side. This is thanks to a phenomenon known as quantum tunneling, and now a team of physicists has measured just how long that process takes.

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Time may be a human construct but that hasn’t stopped physicists from perfecting it.

JILA’s 3D Quantum Gas Atomic Clock Offers New Dimensions in Measurement
https://www.nist.gov/news-events/news/2017/10/jilas-3-D-quan…easurement
“JILA physicists have created an entirely new design for an atomic clock, in which strontium atoms are packed into a tiny three-dimensional (3D) cube at 1,000 times the density of previous one-dimensional (1-D) clocks. In doing so, they are the first to harness the ultra-controlled behavior of a so-called “quantum gas” to make a practical measurement device.”

Jun Ye: Let There Be Light (and Thus, Time)


Dr. Jun Ye, professor of physics at the University of Colorado at Boulder and a fellow of both the National Institute of Standards and Technology and JILA, explains how lasers are used to manipulate atoms inside and out for ultra-precise clocks.

Ultra-Accurate Clocks Lead Search for New Laws of Physics.

Ultra-Accurate Clocks Lead Search for New Laws of Physics


Atomic clocks are letting physicists tighten the lasso around elusive phenomena such as dark matter.

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About the Presenter:
After getting his Ph.D. in physics from UC San Diego, Garrett moved to Maui, seeking an optimum balance between surfing and his theoretical research. While pursuing an unanswered question at the heart of Quantum Field Theory, he began to develop what he called “An Exceptionally Simple Theory of Everything,” which proposed a unified field theory combining particle physics and Albert Einstein’s theory of gravitation. His story and work have been featured at TED, in Outside Magazine, The New Yorker, Surfer, and recently in Scientific American.

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About TEDx
In the spirit of ideas worth spreading, TEDx is a program of local, self-organized events that bring people together to share a TED-like experience. At a TEDx event, TEDTalks video and live speakers combine to spark deep discussion and connection in a small group. These local, self-organized events are branded TEDx, where x = independently organized TED event. The TED Conference provides general guidance for the TEDx program, but individual TEDx events are self-organized.* (*Subject to certain rules and regulations)

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