Практикум

А

А TWO-DIMENSIONAL ATOM GAS (2DAG) has been optically trapped for the first time. Two-dimensional arrays of particles are rare: 2-dimensional electron gases (2DEG) are at the heart of the quantum Hall effect, and planar sprinklings of atoms at the surface of a superfluid have been studied. But only now have physicists been able to trap atoms in a quasi-2-dimensional pancake only 200 nm thick about 800 nm above a gold substrate. Harald Gauck and his colleagues at the University of Konstanz use a battery of lasers to cool and confine argon atoms in what is essentially a planar resonant cavity for atom waves. By shaping the local light fields, the researchers hope to fashion planar structures such as miniaturized atom interferometers and even one-dimensional atom waveguides. The planar gas of argon atoms is not dense enough to fall into a Bose-Einstein condensate, but the Konstanz optics setup might lend itself to achieving eventually a 2D condensate.

THE NEOLITHIC TRANSITION IN EUROPE. Human behavior is much more complicated than the behavior of atoms, liquids, or planets. Nevertheless, physicists and mathematicians have attempted to apply their equations in the social sphere; recent examples recounted in Physics News Update include such topics as the arms race, economics, bird flocking, and the making of group decisions. Now two Spanish physicists, have applied diffusion/reaction equations – governing, say, the diffusion of one fluid through another with due allowance for chemical reactions along the way – to the diffusion of agricultural technology into Europe in the early centuries of the Neolithic epoch roughly 10,000 years ago. Such an effort had been tried before, but the model predictions poorly matched the observed anthropological, linguistic, and genetic data. According to Joaquim Fort of the University of Girona, a much better match can be achieved by using equations with additional “time-delay” terms of the type used successfully to model the spread of forest fires and epidemics. In the case of human migration a time delay factor would reflect the fact that generally the offspring of migrating farmers must grow to adulthood before they themselves “diffuse” outwards. Fort believes that mathematical modeling will become even more important to anthropology and history, but only in concert with high-quality data from fieldwork.

RELATIVISTIC SLEIGH RIDE. The December 11 issue of Fermi News seeks to answer the perennial question of how Santa Claus can, in the course of a single night, deliver gifts to each of the world’s 2 billion children. Even if a full-scale quantum computer were to work out the optimum course plan St.Nick must still cover a flight path of some 160 million km and stop at 800 million homes along the way. How does he do it? By traveling at close to the speed of light, of course, which, incidentally, also explains why (thanks to time dilation) Santa never seems to age. The Fermi News article helpfully addresses such questions as to how it is that the fat fellow can fit into Lorentz-contracted chimneys in the first place and how one can determine the color of the Doppler-shifted light emitted by Rudolph-the-rednosed-reindeer at sleigh velocities approaching the speed of light.

WIRE-GUIDED ATOMS. The development of “atom optics” is part of the effort to store, guide, focus, reflect, and perform calculations with atoms in analogy with the ways electrons are used in electronics and photons in photonics. In a new innovation cold lithium atoms from a magneto-optic trap (MOT) were nudged in the direction of a thin current-carrying wire. Although the atoms are neutral, they still feel the magnetic force field, which can be used to send the atoms in two types of trajectory. In one case the atoms spiral in “Kepler” like orbits around and along the wire. In the second case the use of an extra field helps to create a “potential tube” parallel to the wire in which the atoms are guided along the side of the wire. This second guide is especially interesting since the wires can be mounted on a surface, allowing for easy miniaturization of these guides and traps. Physicists at the University of Innsbruck expect that this will allow them to design guides and traps for cold atoms with a variety of different geometries. These can be used to manipulate atoms from Bose-Einstein condensates, or serve as beam splitters or interferometers for guided atoms. Even more complicated integrated atom optics devices and networks, similar to integrated circuits for electrons, can be devised. Some mesoscopic experiments, which now use electrons in solids, might, with this new atom optics tool, be able to use guided atoms moving above a surface.

HOLOGRAMS OF TRANSISTOR INTERIORS can provide maps of electrostatic potentials in that crucial zone beneath the transistor’s gate, where the passage of electrons from emitter to drain can be made difficult or easy, just as a water tap can switch a faucet on and off. Why are such maps necessary? “Within a decade, integrated circuits will consist of transistors 150 atoms long and 50 atoms deep,” according to researchers at the Institute for Semiconductor Physics in Frankfurt (Oder), Germany, and knowledge of the precise whereabouts of dopant atoms will be vital. To this end, the Frankfurt scientists can now produce a subsurface sectional map of the transistor. Electron waves from a transmission electron microscope (in which the quantum wavelike properties of electrons are more important than their particle properties) pass through the thin transistor, where they scatter slightly. These waves are recombined with some unscattered electron waves to form a holographic signal, which encodes in formation about local conditions throughout the section. The electron data can be processed into 2-dimensional images with 10-nm resolution and high sensitivity.

A SINGLE-PHOTON TURNSTILE, a device in which photons are emitted one at a time under controlled circumstances, has been created by a team of scientists form Stanford (US), Hamamatsu Photonics (Japan), and NTT (Japan). Essentially the researchers use the quantization of electrical conductance to produce a quantization of photon emission. They put together a quantum well (the frontier between two thin semiconductor layers) containing a single electron (other electrons are dissuaded from entering because of a “Coulomb blockade” effect) with a quantum well containing a lone (comparably Coulomb blockaded) hole, and then cycle the voltage across the whole stack of layers in such a way that the lone electron and lone hole meet, mate, and make a lone photon. The resulting device, which operates at mK temperatures, is typically a tiny post some 700 nm tall and with a diameter of 200-1000 nm.

B

‘We did not hang around to see if the gun worked’

John Aglionby in Dili

Saturday September 4, 1999

The sound of the smack across my friend’s face echoed like a gunshot. I whipped round to see her clutching her left ear and a fiery man shouting at her: “Get out you foreign dog.”

This appeared to be a signal to the six man with him to attack us, five journalists investigating an attack by pro-Jakarta militias yesterday morning on the pro-independence suburb of Becora in the East Timor capital, Dili. Another man pulled out a pistol. It was only a homemade gun but we did not hang around to see if it would work. Should I have left with the journalists who at that moment were packing their bags to evacuate on a BBC charter flight?

Several of the militiamen followed us briefly but, thankfully, made no serious attempt to prevent our escape. Even more passive were the dozen members of the police’s crack mobile brigade, all armed with automatic rifles and bayonets. The officers made no attempt to intervene at any time: they did nothing when the militiamen barged though their ranks, heading for us, or when the assault began.

The words of UN spokesman David Wimhurst ran through my mind. “The performance of the Indonesian police has been totally inadequate since polling day.”

That was Monday, when 98.6% of East Timorese adults voted, mostly peacefully, on whether to remain part of Indonesia or choose independence.

Since then peace has been hard to find anywhere in the former Portuguese colony, invaded by Indonesia in 1975.

I last left Dili on Wednesday afternoon, to go to the village of Hera 10 miles away, where four people were reportedly killed by militiamen.

The local people described how the militiamen pulled four graduates of the local polytechnic from their car the previous day and took them away. Ten hours later they were dead. The one man who saw the assault is now in hiding, nursing a smashed head and broken arm.

Hate campaign

Far right sets sights on Brandenburg

Ian Traynor in Berlin

Saturday September 4, 1999

“No more money for foreigners”; “Don’t let the bigshots make a pig of you”; “German money for German workers.”

In hundreds of thousands of posters, these neo-Nazi messages of hate and rage are plastered everywhere in the small, depressed east German state of Brandenburg ahead of tomorrow’s election – a vote that threatens to inflict a humiliating defeat on Chancellor Gerhard Schruder’s governing Social Democrats.

The vote could also see the neo-fascists entering the state parliament in Potsdam for the first time since Germany’s unification almost a decade ago.

The mass poster and mailshot campaign is the work of a reclusive millionaire Munich publisher and neo-Nazi leader, Gerhard Frey, who has spent almost J1m in Brandenburg in hopes of repeating last year’s stunning success in taking 13% of the vote in neighboring Saxony-Anhalt.

Mr Frey’s political vehicle is the DVU, or German People’s Union, a phantom political outfit that exists purely by his grace and favor. Its campaign features no public rallies, no debating, no manifestos, and few public faces. Just posters and letters. Yet, pollsters say that the DVU is hovering near the 5% threshold needed to enter the state legislature.

The neo-Nazi vote is notoriously hard to gauage, but Brandenbur is fertile ground for the extreme right – at least 20% of its 2.6 m people are unemployed, there is widespread hostility to foreigners, and the state has the worst record in Germany for racist violence.

Its interior minister, Alwin Ziel, reported this week that so far this year there have been 33 acts of serious violence, many of them against immigrants. When councilors in the town of Farstenwalde stood in silence to mark the death of an Algerian asylum-seeker who was hounded to his death by skinheads, the neo-Nazi councilor, Danilo Wilke, remained seated, nonchalantly reading the extremist German Voice. Most of the state’s 56,000 foreigners stay in after dark and avoid public transport.

“Unfortunately, xenophobia here has become routine,” said Brandenburg’s prime minister, Manfred Stolpe, the regional baron for Mr Shruder’s SPD.

Mr Stolpe has abandoned hope of retaining the 54% majority he seized in 1994, and if the neo-Nazis surmount the 5% hurdle he will, at best, have to seek a coalition partner.

The neo-Nazis” electoral chances are usually hurt by bickering and splintering of their constituency between the three main vehicles – the DVU, the Republicans, and the National Democratic Party, which marshals the skinheads and street bullies.

But this time n Brandenburg, the DVU and the Republicans have a pact that the Republicans will stand down.

“We will succeed in defeating the far-right extremists if all the democratic parties pool their efforts,” said Mr Ziel, a Social Democrat.

But there is little chance of that. The Christian Democrat opposition leader, Jurg Schunbohm, has even been fishing for the neo-Nazi vote himself.

C

`Barbie

A man walks into a store to buy a Barbie doll for his daughter. “How much is that Barbie in the window?” he asks the shop assistant.

In a condescending manner she responds, “Which Barbie?

We have…

- Barbie Goes to the Gym for $19.95

- Barbie Goes to the Ball for $19.95

- Barbie Goes Shopping for $19.95

- Barbie Goes to the Beach for $19.95

- Barbie Goes Nightclubbing for $19.95

- and Divorced Barbie for $265.00.”

The guy asks, “Why is Divorced Barbie $265.00 when all the others are only $19.95?”

“That’s obvious,” the assistant states, “Divorced Barbie comes with Ken’s house, Ken’s car, Ken’s boat, Ken’s furniture…”

A minister dies and is waiting in line at the Pearly Gates.

Ahead of him is a guy who’s dressed in sunglasses, a loud shirt, leather jacket, and jeans.

Saint Peter addresses this guy, “Who are you, so that I may know whether or not to admit you to the Kingdom of Heaven?”

The guy replies, “I’m Joe Cohen, taxi-driver, of Noo Yawk City.”

Saint Peter consults his list. He smiles and says to the taxi-driver, “Take this silken robe and golden staff and Enter the Kingdom.”

The taxi-driver goes into Heaven with his robe and staff.

Next it’s the minister’s turn. He stands erect and booms out, “I am Joseph Snow, pastor of Saint Mary’s for the last 43 years.”

Saint Peter consults his list. He says to the minister, “Take this cotton robe and wooden staff and enter the Kingdom.”

“Just a minute,” says the minister, “That man was a taxi-driver and he gets a silken robe and golden staff. How can this be?”

“Up here, we work by results,” says Saint Peter.

“While you preached, people slept; while he drove, people prayed.”

Once, in a small town, lived a man named Jack.

Everyone in town knew Jack as a very optimistic person.

Jack, whenever placed in a terrible situation would say,

‘It could have been worse.’

Everyone in the town was tired of hearing Jack say that so one day they decided to lie to Jack.

They went up to him and said, ‘Jack, the baker Bob found his wife in bed with another man last night! He shot the man and then himself!

Isn’t it terrible???’

Then Jack said, ‘Well, yes it’s terrible, but it could’ve been worse!’

The townspeople said, ‘How could THAT possibly be worse?’

Then Jack replied, ‘Well, if it had been the night before I would’ve been dead!’

Before You Get Married

“Honey,” said a husband to his wife, “I invited a friend home for supper.”

“What? Are you crazy? The house is a mess, I didn’t go shopping, all the dishes are dirty, and I don’t feel like cooking a fancy meal!”

“I know all that.”

“Then why did you invite a friend for supper?”

“Because the poor fool’s thinking about getting married.”

A group of Americans was touring Ireland. One of the women in the group was a real curmudgeon, constantly complaining. The bus seats are uncomfortable. The food is terrible. It’s too hot. It’s too cold. The accommodations are awful.

The group arrived at the site of the famous Blarney Stone.

“Good luck will be followin’ ya all your days if you kiss the Blarney Stone,” the guide said. “Unfortunately, it’s being cleaned today and so no one will be able to kiss it. Perhaps we can come back tomorrow.”

“We can’t be here tomorrow,” the nasty woman shouted. “We have some other boring tour to go on. So I guess we can’t kiss the stupid stone.”

“Well not”? the guide said, “it is said that if you kiss someone who has kissed the stone, you’ll have the same good fortune.”

“And I suppose you’ve kissed the stone,” the woman scoffed.

“No, ma’am,” the frustrated guide said, “but I’ve sat on it.”