Tag: quantum dynamics

Say Hello To My Little Friend: The Atom, Imaged

atom_photo

I am fascinated with outer space, this is true. But if you stop to think about it, the inner space between the atoms is just as awe-inspiring as the vast distances separating the planets, stars and galaxies. In actuality the volume inside an hydrogen atom is essentially empty; the single electron “orbits” (if we consider the simple Bohr model of the atom) the central proton at a huge distance. It’s analogous to a quantum star system, where a planet orbits its parent star, hundreds of millions of miles away.

However, atoms aren’t as simple as Niels Bohr’s famous model (although Bohr’s model is none-the-less important as it always has been). The electrons occupy a cloud, rather than specific orbits, and the electron’s position cannot be defined as a point, more a statistically defined volume. As dictated by quantum theory these clouds vibrate at certain frequencies, depending on the electron energy. These electron energies are analogous to the simple electron “shells” physicists refer to in the textbooks; each progressively higher shell occupying a higher energy state. In reality, in the slightly fuzzy quantum world, the frequency of electron oscillation increases with energy.

Examples of electron atomic and molecular orbitals. The "lobes" are representative of the electron clouds surrounding the nuclei
Examples of electron atomic and molecular orbitals. The lobes are representative of the electron clouds surrounding the nuclei (source)

When I was in university, I loved seeing the different modes of electron energy in 3D visualizations of the atom (pictured right). Lobes of electron clouds vibrating at different energies seemed to make sense. But now, for the first time, the clearest photographs of a single atom have been taken, with lobes of electron clouds — as predicted by quantum theory — intact.

This research soon to be published in the journal Physical Review B, demonstrates detailed images of a single carbon atom’s electron cloud (pictured top). Taken by Ukrainian researchers at the Kharkov Institute for Physics and Technology in Kharkov, Ukraine, these images clearly show the electron cloud in two energy states.

This amazing feat was accomplished using a field-emission electron microscope. Although this microscope has aided physicists since the 1930’s to image the vanishingly small, the Ukrainian researchers have developed a new way of making the tool so sensitive, single atoms can be imaged. After arranging a ridged chain of carbon atoms (only tens of atoms long) inside a vacuum chamber, the researchers passed 425 volts through the atoms. At the tip of the chain, the end carbon atom emitted its electrons and a surrounding phosphor screen captured an image. This image was of the electron cloud surrounding the single carbon atom.

Up until this point, field emitting microscopes have only been able to resolve the arrangement of atoms in a sample. This is the first time physicists have been able to see the structure of an electron cloud around an atom.

It’s always nice to validate a bedrock physics theory with photographic evidence, it’s exciting to think what the Kharkov Institute scientists will do next…

Source: Insidescience.org

Are Wormholes Quantum Vacuum Cleaners?

The wormhole could form shortcuts in space-time (www.designboom.com)

General relativity and quantum dynamics don’t get along too well.

If you had to compare the two it would be like evaluating the differences between a Mac and a PC; both are well-honed examples of modern computing, but both are hopelessly incompatible. In computing, this isn’t too much of a problem, you either use a PC or a Mac, or you buy both for their individual strengths (and then complain about Microsoft regardless). But in physics, when you’re trying to find a unified theory, the fact that gravity has been outcast from the Standard Model club, tough questions need to be asked. Although there is some hope being generated by superstring theory, quantum gravity has a long way to go before it can be proven (although high energy particle accelerators such as the LHC will be able to help out in that department).

As pointed out by KFC at the Physics ArXiv Blog, “physicists have spent little time bothering to find out” how quantum mechanics operates in a curved space-time as predicted by Einstein’s general relativity. But now, a physicist has done the legwork and imagined what a quantum particle would do when faced with one of the most famous loopholes in space-time; the mouth of a wormhole. And what popped out of the equations? Another curious force called the “quantum anticentrifugal force.”

So, what’s that all about?

Rossen Dandolo from the Universite de Cergy-Pontoise, France, decided to focus on the wormhole as this is the most extreme example of curved space-time there is. Wormholes are used over and over in sci-fi storylines because they are theorized to link two locations in space-time (thereby forming a shortcut), or even two different universes. As this is space-time we’re talking about, there’s also some possibility of using wormholes as passages through time. Although wormholes sound like a whole lot of fun, in practical terms, they won’t be of much use without some exotic energy to hold the throat of the wormhole open.

Dandolo, however, isn’t too interested in traversing these holes in space-time, he is interested in finding out how a particle acts when in the locality of the mouth of a wormhole.

Beginning with some bedrock quantum theory, Dandolo uses the Heisenberg Uncertainty Principal that stipulates that you cannot know a particle’s momentum and location at the same time. So far, so good. Now, looking at a prediction of general relativity, the wormhole will warp space-time to the extreme, stretching the space around the hole. This space-time stretching causes an increase in uncertainty in the location of the particle. As uncertainty in location increases, the uncertainty in momentum decreases. Therefore, the closer you get to the mouth of the wormhole, the momentum, and therefore particle energy, will decrease.

This interaction between the stretching of space-time and quantum properties of the particle has some amazing ramifications. If the particle’s energy deceases the closer it gets to falling into the wormhole, the wormhole is acting as a potential well; particles will move to a location with less energy. Therefore, a new force — combining both quantum dynamics and general relativity — is acting on particles that stray close to the wormhole: an anticentrifugal force.

This makes wormholes particle vacuum cleaners, exerting a space-time curvature effect on the quantum qualities of matter.

General relativity and quantum dynamics might have some stronger ties than we think…

Source: Wormholes Generate New Kind of Quantum Anticentrifugal Force, by KFC on the ArXiv Blog.