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General Board / Quantum Zeno effect
« on: December 11, 2008, 10:24:32 PM »


This has come to be known as the Heisenberg Uncertainty Principle. The physicist Werner Heisenberg suggested that just by observing quantum matter, we affect the behavior of that matter. Thus, we can never be fully certain of the nature of a quantum object or its attributes, like velocity and location. This idea is supported by the Copenhagen interpretation of quantum mechanics. Posed by the Danish physicist Niels Bohr, this interpretation says that all quantum particles don't exist in one state or the other, but in all of its possible states at once. The sum total of possible states of a quantum object is called its wave function. The state of an object existing in all of its possible states at once is called its superposition. According to Bohr, when we observe a quantum object, we affect its behaviour. Observation breaks an object's superposition and essentially forces the object to choose one state from its wave function. This theory accounts for why physicists have taken opposite measurements from the same quantum object: The object "chose" different states during different measurements.


An unstable particle, if observed continuously, will never decay. One can nearly "freeze" the evolution of the system by measuring it frequently enough in its (known) initial state. The meaning of the term has since expanded, leading to a more technical definition: time evolution can be suppressed not only by measurement: The quantum Zeno effect is the suppression of unitary time evolution caused by quantum decoherence in quantum systems provided by a variety of sources: measurement, interactions with the environment, stochastic fields, and so on. As an outgrowth of study of the quantum Zeno effect, it has become clear that application to a system of sufficiently strong and fast pulses with appropriate symmetry also can decouple the system from its decohering environment. The name comes from Zeno's arrow paradox which states that, since an arrow in flight is not seen to move during any single instant, it cannot possibly be moving at all.

An earlier theoretical exploration of this effect of measurement was published in 1974 by Degasperis et al. and Alan Turing described it in 1954:

Quote
It is easy to show using standard theory that if a system starts in an eigenstate of some observable, and measurements are made of that observable N times a second, then, even if the state is not a stationary one, the probability that the system will be in the same state after, say, one second, tends to one as N tends to infinity; that is, that continual observations will prevent motion...

resulting in the earlier name Turing paradox. The idea is contained in the early work by John von Neumann, sometimes called the reduction postulate. According to the reduction postulate, each measurement causes the wavefunction to "collapse" to a pure eigenstate of the measurement basis. In the context of this effect, an "observation" can simply be the absorption of a particle, without an observer in any conventional sense. However, there is controversy over the interpretation of the effect, sometimes referred to as the "measurement problem" in traversing the interface between microscopic and macroscopic. Closely related (and sometimes not distinguished from the quantum Zeno effect) is the watchdog effect, in which the time evolution of a system is affected by its continuous coupling to the environment.

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General Board / " la folie... pas du tout"
« on: December 11, 2008, 09:33:42 PM »


"He Loves Me, He Loves Me Not" is a clever French film that begins as a romance and ends up as a thriller. I personally like this kind of story, in which nothing you see at the beginning is what it seems. [The most famous example, perhaps, is Alfred Hitchcock's "Vertigo"] While this movie might prove too deceptive and cynical [or even a bit cruel] for some viewers, I think it wll prove rewarding for those who like films that `think outside the box'. The movie begins much like any standard romance. Angelique [Audrey Tautou], a promising young artist, is madly in love with Loic [Samuel Le Bihan], a successful cardiologist. She sends some flowers and a painting she did to his office to show her affections. She is house sitting for a family who has gone away for a year. Her life seems almost perfect until it dawns on her that the doctor doesn't keep the promises he makes to her -- he doesn't show up for dates, he refuses to leave his wife, etc. Slowly, she sinks into a depression. She later plots her revenge against her `unfaithful' man. But what is really going on between these two?

Tautou is the French actress who charmed audiences around the world a while back as "Amelie." Here, she proves she is more than a big smile, wide eyes and an odd hairdo; in fact, she looks completely different. She is a most accomplished actress. Samuel Le Bihan is first rate as the object of her affection. The movie is in French with English subtitles. These do not bother me in the least, but I am well aware that some people refuse to watch a movie in a foreign language. I say that that's their loss.


I'm British and am not really supposed to like the French -- I'm not sure why, I think it's something to do with Agincourt, Napoleon and the Eurovision Song Contest. Despite this I am frankly enamored with them because they're so much cooler than we could ever be. It is because they are so comfortable in their own skin that they can get away with movies which would be embarrassing if made by the British and ghastly if made by the Americans. " la folie... pas du tout" falls into this category. Sartre had a gift for doing philosophy in a hip, wine drinking, story telling, bohemian way. This movie has done a disturbing, psychological, tragic romance in a beautiful, sumptuous, fist-bitingly lovely way. I'm sure it's something to do with being French.

The only thing that irked me was that the script and plot were both repeatedly, albeit momentarily, clumsy. For a movie so graceful in terms of acting and direction it was sad that the screenplay couldn't quite keep pace. On the upside the acting was great. I'm probably biased as it's only a profound laziness that stops me stalking Audrey Tautou, but she was marvelous. The story moved quickly and even the marginally avant garde perspective shift was beautifully achieved. The conclusion is wonderfully dark and leaves you feeling that the plot has been going somewhere and that you've arrived there quite unexpectedly.

Had the script been a little more polished I'd have given it more marks. Having said that I don't expect that anybody involved in the movie will be crying themselves to sleep because some random internet bloke has given them 8 out of 10.

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General Board / Re: Presidential Hopeful ...
« on: December 11, 2008, 09:18:06 PM »
The case against Blagojevich just gives a glimpse of the gangsterism and money-grubbing that characterize official politics in the U.S., involving both big business parties. Democratic and Republican officeholders routinely trade government favors for cash, whether in the form of campaign contributions or outright bribes. While it appears that the governor of Illinois is a particularly crude, foul-mouthed and stupid practitioner of capitalist politics, he is not an aberration. Conversations similar in substance, if not style, to those made public in the Blagojevich probe will be taking place today in government offices and political headquarters in every state and throughout Washington DC.

The scandal is clearly only in its early stages, however. The affidavit itself bears the signs of having been written in haste, and the decision to use that procedure rather than present an indictment to a grand jury suggests that Fitzgerald made a last-minute decision to have Blagojevich arrested, perhaps to forestall the governor appointing himself as a successor to Obama. He now must hold a preliminary hearing or formally indict Blagojevich within 20 days.

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