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Carrier multiplication (CM) is a process in which absorption of a single photon produces not just one but multiple electron-hole pairs. This effect is a potential enabler of next-generation, high-efficiency photovoltaic and photocatalytic systems.

Luzi and Clovis will like it ... :-)

A team led by Robert Wolkow at Canada's National Institute for Nanotechnology in Edmonton, Alberta, has discovered that single silicon atoms, sitting in an electron-doped silicon lattice that is blanketed with hydrogen, provide electronic structures with

This is the guy of Luzy's joke: "Dear, this is not what it seems. I can explain EVERYTHING!"

yeah an interesting theory, definitely worth following. But it is far from being mature, and a lot of work remains before saying that it is viable or not... I posted something on this some time ago (http://www.diigo.com/user/pacome/horava_theory) and proposed to do smthing on it in the idea storm (our new creative game...), which didn't have a lot of success... I like also the idea of matrix gravity (see Matrix general relativity: a new look at old problems, Ivan G Avramidi, CQG 21, 103)

you are among what???

I stop complaining about "useless" research such as infeasible invisibility devices... At least I start to understand why Italy is a country with one of the highest publication rates per researcher.

impressive for us non-physicists

"In an effort to help solve the black hole information paradox that has immersed theoretical physics in an ocean of soul searching for the past two years, two researchers have thrown their hats into the ring with a novel solution: Lasers. Technically, we're not talking about the little flashy devices you use to keep your cat entertained, we're talking about the underlying physics that produces laser light and applying it to information that falls into a black hole. According to the researchers, who published a paper earlier this month to the journal Classical and Quantum Gravity (abstract), the secret to sidestepping the black hole information paradox (and, by extension, the 'firewall' hypothesis that was recently argued against by Stephen Hawking) lies in stimulated emission of radiation (the underlying physics that generates laser light) at the event horizon that is distinct from Hawking radiation, but preserves information as matter falls into a black hole."

Theoretized 80 years ago was Breit-Wheeler pair production in which two photons result in an electron-positron pair (via a virtual electron). It is a relatively simple Feynmann diagram, but the problem is/was how to produce in practice a high energy photon-photon collider... The collider experiment that the scientists have proposed involves two key steps. First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light. The next stage of the experiment involves a tiny gold can called a hohlraum (German for 'empty room'). Scientists would fire a high-energy laser at the inner surface of this gold can, to create a thermal radiation field, generating light similar to the light emitted by stars. They would then direct the photon beam from the first stage of the experiment through the centre of the can, causing the photons from the two sources to collide and form electrons and positrons. It would then be possible to detect the formation of the electrons and positrons when they exited the can. Now this is a good experiment... :)

True, but isnt it E2=(pc)^2 + (m0c^2)^2 such that for photons E\propto{pc} and for mass E\propto{mc^2}. I agree it will take a lot of energy, but this assumes that that wont be the problem at least. The question therefore is whether the mass flow of the photon rocket (fuel consumed to create photons, eg fission/fusion) is higher/lower than the mass flow for e-p creation. You are probably right that the low e-p cross-section will favour direct use of photons to create low thrust for long periods of time, but with significant power available the ISP might be higher for e-p pair creation.

In essence the equation tells you that for photons with zero rest mass m0 all the energy will be converted to momentum of the particles. If you want to accelerate e-p then you first spend part of the energy on creating them (~511 keV each) and you can only use the remaining energy to accelerate them. In this case the equation gives you a lower particle momentum which leads to lower thrust (even when assuming 100% acceleration efficiency). ISP is a tricky concept in this case because there are different definitions which clash in the relativistic context (due to the concept of mass flow). R. Tinder gets to a I_SP = c (speed of light) for a photon rocket (using the relativistic mass of the photons) which is the maximum possible relativistic I_SP: http://goo.gl/Zz5gyC .

Quantum chemical simulations reveal an unprecedented relationship between the mechanism of carbon nanotube growth and hydrocarbon combustion processes. Results of these simulations illustrate the importance in the role of carbon chemical bonding and molecular transformations in CNT growth.

A group of researchers from Austria have sent twisted beams of light across the rooftops of Vienna. It is the first time that twisted light has been transmitted over a large distance outdoors, and could enable researchers to take advantage of the significant data-carrying capacity of light in both classical and quantum communications. Although the data rate is not very high, it could offer a way to provide unhackable data links via space. Would provide an edge over terrestrial fibre optics?

NASA validates the EmDrive (http://emdrive.com/) technology for converting electrical energy into thrust. (from the website: "Thrust is produced by the amplification of the radiation pressure of an electromagnetic wave propagated through a resonant waveguide assembly.")

I have to join the skeptics on this one ...

The first complete theory of how plasmons produce "hot carriers" has been developed by researchers in the US. The new model could help make this process of producing carriers more efficient, which would be good news for enhancing solar-energy conversion in photovoltaic devices.

I did not read the paper but what is further down written in the article, does not give much hope that this actually gives much more insight than what we had nor that it could be used in any way to improve current PV cells soon: e.g. "To fully exploit these carriers for such applications, researchers need to understand the physical processes behind plasmon-induced hot-carrier generation. Nordlander's team has now developed a simple model that describes how plasmons produce hot carriers in spherical silver nanoparticles and nanoshells. The model describes the conduction electrons in the metal as free particles and then analyses how plasmons excite hot carriers using Fermi's golden rule - a way to calculate how a quantum system transitions from one state into another following a perturbation. The model allows the researchers to calculate how many hot carriers are produced as a function of the light frequency used to excite the metal, as well as the rate at which they are produced. The spectral profile obtained is, to all intents and purposes, the "plasmonic spectrum" of the material. Particle size and hot-carrier lifetimes "Our analyses reveal that particle size and hot-carrier lifetimes are central for determining both the production rate and the energies of the hot carriers," says Nordlander. "Larger particles and shorter lifetimes produce more carriers with lower energies and smaller particles produce fewer carriers, but with higher energies."

Two research teams have designed an optical gate that can 'switch off' a stream of photons as well as store them ... good news for optical communications as well as future photon-based quantum information systems.

So basically we can photograph light now. Not just detect photons but photograph LIGHT WAVES. Really clever setup BTW.

Cornell applied physicists have demonstrated an unprecedented method of control over electron spins using extremely high-frequency sound waves - new insights in the study of the spin of the electron. Crazy idea but, no further need for complicated quantum encryption techniques of sound signals?

Just out - I wish I could understand this :(

ignorance is a bliss :)

Of interest for debris monitoring and SSA? It has been suggested in the kelvins discussions.....

this is something that I think would really make sense to look closer into, also checking what ESA might have already done on it