Archive for August, 2007

Huntin’ for quantum gravity

Saturday, August 25th, 2007

On the tiniest scale, spacetime ain’t flat at all but a-bubblin and a-fizzin with virtual particles leapin in ‘n outta existence. Quantum gravity, say them cosmologists, is a kinda foam.

Ain’t nobody observed quantum gravity. But this week, them astrogawpers say they might have seen some indirect evidence while a-starin and a-gogglin at Markarian 501, an active galaxy 300 million light years from Earth that flared up in 2005.

The thinkin’ is that quantum foam makes life hellish for photons which have to zip through the quantum hills and valleys that it forms, causin’ them to deviate, ever-so-slightly, from the straight and true. That deviation means two photos travellin’ in the same direction from the same place will take different routes. And the difference can be measured in their arrival times over very long distances, like the 300 milion light years from Markarian 501.

So when it flared up in 2005, a few astrobods got out their stopwatches and started a-countin and a-timin the gamma rays as they arrived, using a machine called MAGIC in the Canary Islands.

Now the results have been totted up and published on the arXiv, but no drum rolls please.

The team ain’t sure what they seen. Sure, them photons do seem to get filtered according to NRG, which is what ya’ll expect if quantum foam were playin havoc with em. (The team is able to rule out other dispersion effects on the photons, such as QED plasma refraction, which is kinda excitin’.)

But they still have a problem: ain’t nobody worked out how the flares generate gamma rays in the first place. Maybe the photons ain’t all emitted at the same time, p’raps there is some mechanism in active galactic flares that makes photons look as if they bin filtered by quantum foam.

So we’re left a-hangin. What we need is more data from different kindsa flares. And some a-sweatin and a-toilin by them astrotheorists to tell us what kinda observations will tease all this apart.

Ref: arxiv.org/abs/0708.2889: Probing Quantum Gravity using Photons from a Mkn 501 Flare Observed by MAGIC

Invasion of the jivin’ nano-shrooms

Friday, August 24th, 2007

Convertin’ a constant force into an oscillatin’ one is a useful trick. Ya’ll seen em: gravity-powered pendulums and wind-powered turbines for example, them both set machines a-spinin and a-swingin by exploitin’ a constant force.

Them machines might work sweetly at macroscopic scales but ain’t nobody cracked it on the nanoscale even though nanobods are a-chompin at the bit to reproduce this trick. The trouble is that gravity ain’t strong enough at this level and as for wind, who you kiddin?

That leaves only tricky-dicky forces from the dizzy world of electrostatics and magnetics and these are so poorly understood on tiny scales that them nanobods are still a-wondrin and a-ponderin over how to harness them.

But Hyun “Mighty” Kim and his crew at the University of Wisconsin-Madison say they cracked it.

Their device is a kinda nano-mushroom that stands between the plates of a capacitor, in a constant DC field.

Give the mushroom a push and it leans towards the source electrode where electrons tunnel across into the mushroom head. The DC field exerts a force on this extra charge on the ’shroom, pushing it towards the drain electrode where the electrons jump ship. The force disappears and the mushroom’s stiffness sends it swinging back to the source again like metronome, and the process starts again.

Voila! A nanomechanical oscillator that converts a a constant force into an oscillation.

Them nanobods are gonna be cockahoop over this one, betcha!

Ref: arxiv.org/abs/0708.1646: Self Excitation of Nano-Mechanical Pillars

How to get ahead in evolutionary computing

Thursday, August 23rd, 2007

Ya’ll know that connectedness is an important feature of small world networks. And that various busy bodies have worked out the best connected film stars, scientists, toilet attendents etc by analysing the network of links between these people in their various professions.

Very clever and, at one time, even kinda intrestin’.

Now Juan “Don” Merelo and a buddy at the University of Granada in Spain asks over the course of 16 pages: “Who is the best connected researcher in evolutionary computing?”

Who cares?

I guess Don cares and to be fair, he’s done a thoroughly entertaining job on this piece of research.

And if he’s lookin for work, he ain’t gonna do himself any harm with this magnificent arselickin’ extravaganza.

Ref: arxiv.org/abs/0708.2021: Who is the Best Connected EC Researcher? Centrality Aanalysis of the Complex Network of authors in Evolutionary Computation

Quantum RAM

Wednesday, August 22nd, 2007

If yer gonna build a quantum computer, yer gonna need some quantum memory to store qubits.

Enter quantum random access memory–which like most quantum things is just like plain old vanilla RAM except all a-ghostly and a-spooky. Brrrrr.

Here’s how RAM works. Each memory cell is connected to a circuit tree in which the branches can be switched on or off. Addressing a single memory cell means arranging the switches so that the only path through the circuit tree goes to the cell in question.

One important problem is how many switches yer have to pull to address a specific memory cell. In conventional RAM it’s in the 2^n ballpark (where n is the number of cells).

Now Seth “Lurver” Lloyd at MIT and a few buddies in Italy have worked out a quantum memory architecture that requires on n switches to be thrown (or thereabouts).

That’s a significant reduction. What’s more, the team says the idea can be used to improve the performance of classical RAM. Reducing the switching from 2^n to n could dramatically reduce power consumption in conventional RAM.

And ain’t we all lookin for greener RAM?

Ref: arxiv.org/abs/0708.1879: Quantum Random Access Memory

The physics of poverty

Tuesday, August 21st, 2007

Why are poor countries unable to make themselves richer by exporting to developed countries? What keeps ‘em in this poverty trap?

Economists ain’t got a clue, otherwise they’d a told us, right? But this week a group of physicists have unveiled some ideas with the kinda insight that might just turn this field on its head. Ah don’t mind telling ya’ll, it looks exciting.

There ain’t no shortage of theories about poverty but most depend on economists’ a-spoutin and a-splutterin a whole loada hocus pocus.

The problem with economists is that to make their theories work, they have to guess what factors are the most important for economic success–p’raps it’s the cost of labour or the price of land or the level of technological sophistication that’ s important.

But who knows for sure? Certainly not them economists!

That’s why a new approach by César “Pony” Hidalgo and pals at the University of Notre Dame, is important.

Ref: arxiv.org/abs/0708.2090: The Product Space Conditions the Development of Nations

More after the jump…

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Dim outlook for solar flare forecasting

Sunday, August 19th, 2007

Yep, looks like sunshine.

Them weather boys have spent a lotta time a-countin and a-calculatin to let ya’ll know when to head for the beaches. Let’s give em their due: weather forecastin is better than it was and we got so much data that it’s a full time job a-pumpin it into them weather computers.

But on the whole, forecastin could be a whole lot better. Just ask em in New Orleans

So ya’ll can be forgiven for being a lil sceptical when these solar scientists say they gonna use the same techniques for forecastin solar flares.

Eric “Blue” Bélanger at the University of Montreal and a few pals reckon that a weatherman’s number crunchin technique called 4D-VAR can forecast new flares based on the past patterns of old ones.

Them Canadians must be a-wearin rose-tinted specs.

Now ah could be wrong, but ain’t there some important differences between weather systems on Earth and flares on the Sun? Not least of these is that the energy release from solar flares is scale free. So when ya’ll watch a solar flare evolve, no matter how slow it looks, you ain’t got no idea how big it’s gonna be.

That puts em in the same category as earthquakes, stockmarket crashes and forest fires. If them things were forecastable using 4D-VAR, meteorologists would all now be a-sitting back in their Bermudan beach huts, a-smokin cubans and a-suppin manhattans. Instead they’re a-sweatin and a-fussin over stratospheric cloud cover.

So it don’t take too much predictin to see where this kinda solar flare forecastin is gonna end up.

Ref: arxiv.org/abs/0708.1941: Predicting Solar Flares by Data Assimilation in Avalanche Models

The first quark nova

Saturday, August 18th, 2007

Them stargazers have been a-gapin’ and a-gawpin’ at a champagne supernova called SN2006g.

A long, long time ago in galaxy far, far away (NGC 1260 in the constellation of Perseus) this mutha blew up big time: the blast was huge, offerin up 100 times more a-rumblin and a-tremblin than anything them astrogawpers have seen before.

But how to explain it? Here’s what happens in the conventional model of supernovas : the star runs outta fuel and collapses in on itself with such force that atomic nuclei and electrons fuse forming all kindsa exotic bits ‘n’ pieces but primarily neutrons.

This fusion process releases energy that blasts away the outer layers of the star creatin an explosion.

But this theory don’t produce enough juice to explain a supernova as big as SN2006g.

What could produce more NRG? Denis “Supermarket” Leahy and his buddy Rachid at the University of Calgary have dreamed up a wild n’ wacky alternative. They say that if the star collapses even further, so that atomic nuclei fuse to form quarks, this would release even more energy, in fact justa nuff to explain SN2006g.

Neat eh? (Actually this ah-dear ain’t entirely their own since Ed “Dial M for…” Witten and others have all skinny dipped in the same pool).

If Supermarket Leahy has banged the metaphorical nail on the head, SN2006g is the first quarknova.

For an astrogeek, there ain’t nothin better than a-ferretin out something new up there. A real quarknova should get more than a few people a-hummin and a-whistlin.

Ref: arxiv.org/abs/0708.1787 : Supernova SN2006gy as a First Ever Quark Nova?

The sound of neutrinos

Friday, August 17th, 2007

Them neutrinos are shy critters. Given half a chance, they’ll pass on by without ya’ll ever knowin they bin there.

But when it comes to water, they lurv a lil splashin and a-playin. With a microphone, ya’ll can even hear ‘em. Yep, that’s right. On the rare occasions they do interact with matter, they generate a cascade of particles that create a detectable sound wave.

But a lot of other things like water too, such as fish and humans. And they’re so noisy that they drown out the lil bitty splashin that neutrinos make. Which is why attempts to listen out for neutrinos have so far come to nothin.

But if ya wanna lil bit of peace and quiet, try the South Pole. Earlier this year, them particle people dug a few holes in the ice down there, filled ‘em with microphones and started a-listenin out.

Now the first test results are back, says Justin Vandenbroucke, aka the Buddha of Berkeley. Turns out it is much quieter in the ice than in water (even though the wind does its best to drum up some sounds near the surface.) That’s the good news. The bad news is that sound don’t seem to travel in Antarctic ice as well ya’ll had hoped.

The eventual plan is to search for neutrinos by lookin for their splashin, their flashin and their radio transmishin. But them particle people got a whole lot more work to do before they can combine these methods in a giant detector beneath the ice. And most of that work is in findin out whether acoustic detection is really viable.

So ya’ll come back now and ah’ll letcha know how Buddha boy gets on.

Ref: arxiv.org/abs/0708.2089: Feasibility of Acoustic Neutrino Detection in Ice: First Results from the South Pole Acoustic Test Setup (SPATS)

Nano-electromechanical devices

Thursday, August 16th, 2007

Ya’ll heard of MEMs (micro-electromechanical devices), right? So it was never gonna be long before we got the lowdown on NEMS nano-electromechanical devices. They’re a-comin atcha.

The problem is that to make anything move on the nano scale, ya gotta yank it with an electric field and that means having a metallic conducting layer in there somewhere. Now adding a metal layer makes NEMs heavy, bulky and slow.

But Dominik “Peeble” Scheible at Ludwig-Maximilians University in Germany says he’s souped up the existing design for NEMS to make ‘em faster, lighter and better—yeeehaaa.

Peeble Scheible’s solution is to make NEMs out of a semiconductor such as silicon and create conducting regions within the silicon by implanting dopant atoms using focused ion beams.

He’s even gone and built himself a lil bitty nanobeam resonator out of silicon doped with gallium to prove he can do it. And it is bee-yoo-tiful–it’s nanoform following nanofuntion. A-sleek and a-shiny too. Ah am impressed.

And now ya’ll just sit tight for pico, femto and atto-electromechanical devices.

Ref: arxiv.org/abs/0708.1296: Doped Nano-Electromechanical Systems

The dark matter problem

Wednesday, August 15th, 2007

It ain’t right, this dark matter business. The problem is these galaxies that astronomers are a-peepin and a-starin at: they’re just rotatin too quick for Newton’s beloved gravity to hold em together. So something has to be a-stickin and a-holdin them tight.

Ya’ll bin told that dark matter provides the extra gravitational oomph to stop galaxies flyin apart. For some reason, the notion has stuck. Physicists have squandered more than their fair share of pocket money lookin for dark matter and wot have they got to show for it? Zilch.

But it don’t got to be dark matter says John “Mohawk” Moffat at the Perimeter Institute in Canada. Maybe gravity needs a-nudgin and a-kneedin to fit the data.

The most famous attempt is a quick’n'easy rewrite of Newton called MOdified Newtonian Dynamics or MOND which was proposed by Mordehai “Mouse” Milgrom in 1981. MOND makes gravity stronger at large distances, which stops ‘em galaxies a-rippin and a-tearin themselves apart without invokin dark matter.

But MOND don’t work on much larger scales for clusters of galaxies, which also need something to stop em flyin apart.

So Mohawk Moffat has dreamt up MOdified Gravity or MOG and now fitted it to the data. Works a treat, he says. MOG explains the motions of galaxies and clusters of galaxies without needin dark matter.

What Mohawk needs now is a way a-measurin MOG on planet Earth. Cos ain’t nobody gonna believe him otherwise.

Ref: arxiv.org/abs/0708.126: Testing Modified Gravity with Globular Cluster Velocity Dispersions