Archive for June, 2008

Oil prices: a classic bubble economy?

Tuesday, June 10th, 2008

Oil bubble

The price of oil has quadrupled since 2003. If this dramatic rise were the result of speculation in a bubble economy and not the normal forces of supply and demand, how would you go about proving it?

Try using some well known concepts from statistical physics and complexity theory, says our old friend Didier Sornette at the Swiss Federal Institute of Technology in Zurich.

For economists, the term bubble refers to a situation in which excessive expectations of future price increases cause prices to rise above what can justified by a fundamental valuation.

One of the signatures of such a bubble is a faster-than-exponential growth in prices, something that has been seen in several recent bubbles such as the dotcom boom that busted in 2000, the US house price surge that peaked in 2006 and the sub-prime market which collapsed in 2007.

What creates faster than exponential growth? One possibility is positive feedback mechanisms which reinforce unsustainable prices rises.

So Sornette’s analysis involves identifying the signature of faster-than-exponential growth, which is relatively easy to spot, and then identifying the positive feedback mechanisms that may have caused it. These, he says, are:

(1) Protective hedging against future oil price increases and a weakening dollar whose anticipations amplify hedging in a positive self-reinforcing loop

(2) Search for a new high return investment, following the collapse of real-estate, the securitization disaster and poor yields of equities, whose expectations endorsed by a growing pool of hedge, pension and sovereign funds will transform it in a selffulfilling prophecy;

(3) The recent development since 2006 of deregulated oil future trading, allowing spot oil price to be actually more and more determined by speculative
future markets and thus more and more decoupled from genuine supply-demand equilibrium.

Sornette says this “provides evidence that the recent oil price run-up has been amplified by speculative behavior of the type found during a bubble-like expansion.”

He may well be right but he fails to nail the argument in this paper.

There is another way in which faster-than-exponential price rises can occur and that’s from a faster-than-exponential rise in demand. What Sornette fails to show is that the recent price rises cannot be explained by a faster-than-exponential rise in demand from economies such as China and India.

That’s not beyond the realms of possibility but Sornette seems to ignore it. (Of course, the Chinese and Indian economies may be part of their own larger bubble but that’s another issue).

Sornette says oil price rises may be the result of speculation. Then again, they may not.

Ref: The 2006-2008 Oil Bubble and Beyond

Testing “spooky action-at-a-distance” on the International Space Station

Monday, June 9th, 2008

Entangled ISS

Entanglement is the strange and beautiful property of certain quantum particles to become so deeply linked that they share the same existence. According to quantum theory, that link should be maintained whatever the distance between the particles, whether the width of an atom or the diameter of the universe.

This led Einstein to claim that the instantaneous effects of entanglement would lead to “spooky action-at-a-distance” in violation of special relativity which prevents faster-than-light signals.

Nobody knows how the different predictions of relativity and quantum mechanics can be resolved. However, entanglement has been measured in numerous experiments over relatively short distances on Earth. The tests involve two entangled particles, photons say, being sent to distant experimenters who then perform measurements on them.

In every one of these tests, the results agree entirely with the predictions of quantum mechanics. And yet naysayers continue to unearth loopholes that allow them to claim that there is a way in which the results are fixed, perhaps because quantum mechanics works only only over the short distances that can be exploited on Earth or by the existence some kind of hidden variable that determines in advance how the particles will behave when they are separated.

There is one way to settle the matter for sure: send entangled photons to two orbiting astronauts on board different spacecraft with large relative velocities. That leaves no room for hidden variable theories or any other fix because the peculiarities of special relativity allow both astronauts to claim the measurement on their photon was performed before the other.

Today Anton Zeilinger from the University of Vienna in Austria, says he wants to try just such an experiment and has put together an impressive international team to design and promote idea. The team has submitted its proposal, called Space-QUEST, to the European Space Agency in the hope that one end of the experiment could hosted on the Columbus module, Europe’s orbiting laboratory attached to the International Space Station.

The other observer need only be on the ground since Zeilinger has already proven that single photons can be bounced off orbiting satellites and detected on the ground.

That should please mission planners for the International Space Station which has yet to host a single significant experiment in space. Zeilinger’s Space-QUEST experiment looks like a genuine attempt to push the envelope of physics. The quicker they get it into orbit, the better.

Ref: Space-QUEST: Experiments with Quantum Entanglement in Space

In case ya missed em…

Sunday, June 8th, 2008

The pearls from the physics arxiv blog this week

Supernova echoes give first glimpse of ancient explosions

Which way does antimatter fall?

The science of scriptwriting

Why do online opinions evolve differently to offline ones?

Western Europe warming much faster than expected  

Hot ‘n’ cold

Saturday, June 7th, 2008

The best of the rest from the physcis arXiv this week:

Eternal Inflation: Prohibited by Quantum Gravity?

New Mechanics of Traumatic Brain Injury

From Dark Energy and Dark Matter to Dark Metric

BEC dark matter can explain collisions of galaxy clusters

Superantenna Made of Transformation Media

Common Features in Electronic Structure of the Fe-Based Layered Superconductors from Photoemission Spectroscopy

Western Europe warming much faster than expected

Friday, June 6th, 2008

European warming

There’s little doubt these days over whether the planet is heating up. Temperature measurements clearly show the trend and in recent years, computer models of the Earth’s climate have been able to reproduce these increases pretty accurately when carbon dioxide is injected into their virtual atmospheres.

Where climate models fall down, however, is in predicting how the climate will change on a regional scale. The Netherlands, for example, is represented by a single grid square in global climate models. So that makes it hard to work out how global patterns may influence the climate in the Netherlands.

Today, a group of meterologists from the Royal Netherlands Meterological Institute (KNMI), the Dutch weather forecasting outfit, examine warming trends in western Europe and say the current models of regional climate change have vastly underestimated the rate of change. Yep, that’s underestimated.

What the team has done is identify many of the reasons why regional models fall down. They say the models fail to account for stronger wind circulation patterns in winter and spring, misrepresent the North Atlantic Current that brings warm water from the  equator  to western Europe and underestimate the amount of sunshine in some places. There are also important differnces between observed and modelled effects of aerosols and snow at various places and times too.

That’s important to know because it should be possible to fix the regional climate models  to take account of these effects. At least, in theory.In the meantime, Western Europe is warming much faster than regional climate models have suggested. The message from KNMI is that you live in the Netherlands (or anywhere else in Western Europe), stock up on ice cubes and suncream.

Ref: Western Europe is Warming Much Faster Than Expected

Why do online opinions evolve differently to offline ones?

Thursday, June 5th, 2008

 Online opinions

The way in which opinions form, spread through societies and evolve over time is a hot topic among researchers because of their increasing ability to measure and simulate what’s going on.

The field offers some juicy puzzles that look ripe for picking by somebody with the right kind of insight. For example,  why do people bother to vote in elections in which they have little control over the result when a “rational” individual ought to conclude that it is not worth taking part.

A similar conundrum is why people contribute to online opinion sites such as Amazon‘s book review system or the Internet Movie Database’s (IMDB) ratings system. When there are already a hundred 5-star reviews, why contribute another?

Today Fang Wu and Bernardo Huberman at the HP Laboratories in Palo Alto present the results of their analysis of this problem. And curiously, it looks as if online opinions form in a subtley different way to offline ones.

The researchers studied the patterns of millions of opinions posted on Amazon and the IMDB and found some interesting trends. They say:

Contrary to the common phenomenon of group polarization observed offline, we measured a strong tendency towards moderate views in the course of time.

That might come as a surprise to anyone who has  followed the discussion on almost any online forum but Wu and Huberman have an idea how moderation seems to evolve.  They suggest that people are most likely to express a view when their opinion is different from the prevailing consensus because such a contribution will have a bigger effect on the group.

They tested the idea  by looking at the contributions of people who added detailed reviews against those who simply clicked a button. Sure enough, those who invest more effort are more likely to have an opposing view. It is these opposing views that tend to moderate future views.

By contrast, sites such as Jyte in which users can only click a button to give their opinion tend to show herding behaviour in which people copy their peers, just as they often do offline.

Wu and Huberman’s analysis raises more questions than answers for me. But they point out that the study of online opinions has been neglected until now.  That looks set to change.

Ref: Public Discourse in the Web Does Not Exhibit Group Polarization

The science of scriptwriting

Wednesday, June 4th, 2008


You don’t have to delve far into the realms of scriptwriting before you’ll be pointed towards a book called Story by Robert McKee, which explains why scriptwriting is more akin to engineering than art. McKee examines story-telling like a biologist dissecting a rat. But after taking it apart, he explains how to build a story yourself using rules that wouldn’t look out of place in a computer programming text book.

McKee has become so influential that huge numbers of films, perhaps most of them, and many TV series are now written using his rules. But the real measure of his success is that there are even anti-McKee films such as Adaptation that attempt to burst McKee’s bubble.

Given that scriptwriting has become so formulaic, shouldn’t science have a role to play in analysing it? That’s exactly what Fionn Murtagh and pals at the Royal Holloway College, University of London have done in a project that analyses scripts in a repeatable, unambiguous and potentially-automatic way.

Using McKee’s rules they compare the script of the film Casablanca, a classic pre-McKee movie, with scripts of six episodes of CSI (Crime Scene Investigation), a classic post-Mckee production, and find numerous similarities.

That’s hardly surprising since McKee learnt his trade analysing films such as Casablanca, so anything written using his rules should have these similarities.

What’s interesting about the work is that Murtagh and mates want to use their technique to develop a kind of project management software for scriptwriting. That’s an ambitious goal but one that might find a handy niche market, particularly since many scripts, TV serials in particular, are now written by teams rather than individuals and so need careful project management from the start.

The challenge for Murtagh and co will be to turn this aproach into a bug-free, easy-to-use package that has the potential to become commercially viable. And for that they’ll almost certainly need some outside help and funding. Anybody got any spare cash?

Ref: The Structure of Narrative: the Case of Film Scripts

Which way does antimatter fall?

Tuesday, June 3rd, 2008


The force of gravity on antimatter has never been directly measured but a growing number of physicists believe that such an experiment is within their grasp. Today, a group attempting to design an experiment called AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) outline their plans to measure this force.

In some ways it’s an ambitious plan. The team wants to build AEGIS at CERN, the European particle physics laboratory near Geneva, where the building blocks of antihydrogen, low energy antiprotons and positrons, are in relatively good supply.

The idea is to fire a beam of antihydogen atoms at a target and see how much they are deflected by gravity.

That’s easier said than done. Creating a beam of this stuff turns out to be remarkably tricky. The problem is that it’s easy enough to trap antiprotons and positrons in electromagnetic fields. It’s even fairly straightforwad to put them together so that they form antihydrogen. The problem is that antihydrogen is neutral and simply falls out of the trap. So some way has to be found to collect and trap these antiatoms.

I know what you’re thinking: why not do the experiment with antiprotons or positrons instead.

People have tried but it’s been impossible to completely remove any residual electromagnetic fields from such experiments. These are many orders of magnitude stronger than gravity and so even the smallest trace of them deflects charged particles by an amount that overwhelms the effect of gravity. That’s why neutral antihydrogen is so important.

Why bother? There are several flavours of general relativity that allow antimatter to experience an opposite gravitational force compared to ordinary matter. Finding evidence for this (or ruling it out) will have important consequences for some serious cosmological conundrums such as why we see so little antimatter around and the value of the cosmological constant.

If these guys get the go-ahead, it’ll be a few years before we hear back from them, but it’ll be worth the wait.

Ref: Formation Of A Cold Antihydrogen Beam in AEGIS For Gravity Measurements

Supernova echoes give first glimpse of ancient explosions

Monday, June 2nd, 2008

Supernova echoes

Back in 2005, Armin Rest from Harvard and a few mates, spotted the echo of a supernova in the Large Magellanic Cloud. The explosion had kicked off some 900 years ago but what Rest and co were seeing was its reflection from cold dark dust in the cloud. Since then, the team has even measured the spectrum of the echo to determine that it was Type 1a supernova

Impressive work but Team Rest have not been idle. They have been busy hunting for other echos and today it looks as if they’ve come up trumps. Instead of looking for echos from the Large Magellanic Cloud, the team looked at the Milky Way (a harder task because it takes up a much larger portion of the sky) and found numerous clusters of echos from two recent supernova: Tycho (SN1572) observed by the Danish astronomer Tycho Brahe in 1572 and Cassiopeia A, which went more or less unobserved when it exploded in 1667.

This is important for astronomers because it gives them access to a a kind of exotic wayback machine. All of a sudden, they can study the physics of these supernovae at the moment they exploded and compare that with the properties of the remnants today.What’s more, by looking for echoes of different supernovae that have reflected off the same dustcloud, they have a way to directly measure the distance between them. They conclude that Cassiopeia A is (probably) 1900 light years further away from us than Tycho.

So it provides a new way to measure distance too.

The team has now begun a program to look for the echoes from five other supernova that have occured in the last 2000 years or so. Expect to hear more about that in the near future

Ref: Scattered-light Echoes from the Historical Galactic Supernovae Cassiopeia A and Tycho (SN 1572)

In case ya missed ’em…

Sunday, June 1st, 2008

The pearls from this week’s arXivblog:

VoIP threatened by steganographic attack

The surprisingly rich physics of peeling paper

Friction-free sliding observed in nanoparticles

How to turn a narrow slit into a large window

The mystery of the Plutonic color scheme