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Thread: Instigating a Bosenova

  1. #1 Instigating a Bosenova 
    Administrator KALSTER's Avatar
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    First a quote from the NIST page on recent Bose-Einstein Condensate experiments:

    Working at JILA, physicist Carl Wieman's [pronounced wy-man] team has explored tuning the self-interaction of atoms in a BEC. By making a BEC in a particular isotope of rubidium, rubidium-85, and then changing the magnetic field in which the BEC is sitting, the team is able to adjust the wavefunction's self-interaction between repulsion and attraction. If the self-interaction is repulsive, all the parts of the wavefunction push each other away. If it is attractive, they all pull towards each other, like gravity. Achieving a pure BEC in rubidium-85 required the cloud of atoms to be cooled to about 3 billionths of a degree above absolute zero, the lowest temperature ever achieved.
    Making the self-interaction mildly repulsive causes the condensate to swell up in a controlled manner, as predicted by theory. However, when the magnetic field is adjusted to make the interaction attractive, dramatic and very unexpected effects are observed.
    The condensate first shrinks as expected, but rather than gradually clumping together in a mass, there is instead a sudden explosion of atoms outward. This "explosion," which actually corresponds to a tiny amount of energy by normal standards, continues for a few thousandths of a second. Left behind is a small cold remnant condensate surrounded by the expanding gas of the explosion. About half the original atoms in the condensate seem to have vanished in that they are not seen in either the remnant or the expanding gas cloud.


    They change the properties of the magnetic field trapping the BEC, but how does that affect the forces present in between the constituent atoms? Do they simply tune the field so that it cancels out repulsive forces by destructively interfering with them? Can this only be done with BEC’s because of the uniformity of the wavefunction the atoms collapsed to? Does it mean that the virtual force-carrier particles of each field (van der Waal?) interfere with each other and cancels out? What happens to the energy then, or does it simply revert to the ground zero point energy? What do they mean when they say that “this procedure caused the BEC to implode and shrink beyond detection”?


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  3. #2 Re: Instigating a Bosenova 
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    Quote Originally Posted by KALSTER
    First a quote from the NIST page on recent Bose-Einstein Condensate experiments:

    Working at JILA, physicist Carl Wieman's [pronounced wy-man] team has explored tuning the self-interaction of atoms in a BEC. By making a BEC in a particular isotope of rubidium, rubidium-85, and then changing the magnetic field in which the BEC is sitting, the team is able to adjust the wavefunction's self-interaction between repulsion and attraction. If the self-interaction is repulsive, all the parts of the wavefunction push each other away. If it is attractive, they all pull towards each other, like gravity. Achieving a pure BEC in rubidium-85 required the cloud of atoms to be cooled to about 3 billionths of a degree above absolute zero, the lowest temperature ever achieved.
    Making the self-interaction mildly repulsive causes the condensate to swell up in a controlled manner, as predicted by theory. However, when the magnetic field is adjusted to make the interaction attractive, dramatic and very unexpected effects are observed.
    The condensate first shrinks as expected, but rather than gradually clumping together in a mass, there is instead a sudden explosion of atoms outward. This "explosion," which actually corresponds to a tiny amount of energy by normal standards, continues for a few thousandths of a second. Left behind is a small cold remnant condensate surrounded by the expanding gas of the explosion. About half the original atoms in the condensate seem to have vanished in that they are not seen in either the remnant or the expanding gas cloud.


    They change the properties of the magnetic field trapping the BEC, but how does that affect the forces present in between the constituent atoms? Do they simply tune the field so that it cancels out repulsive forces by destructively interfering with them? Can this only be done with BEC’s because of the uniformity of the wavefunction the atoms collapsed to? Does it mean that the virtual force-carrier particles of each field (van der Waal?) interfere with each other and cancels out? What happens to the energy then, or does it simply revert to the ground zero point energy? What do they mean when they say that “this procedure caused the BEC to implode and shrink beyond detection”?

    Technically they do not pull together, they are pushed together. There is no such thing as attraction.

    You can probably achieve anything they did with common everyday stuff.

    Sincerely,


    William McCormick


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  4. #3  
    Forum Isotope Bunbury's Avatar
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    About half the original atoms in the condensate seem to have vanished in that they are not seen in either the remnant or the expanding gas cloud.
    Fascinating. Where could they have gone?
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  5. #4  
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    They think maybe into molecules that the detector can't detect, but still, as you say, fascinating! And even cooler: Current theory can’t explain it.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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  6. #5  
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    Quote Originally Posted by Bunbury
    About half the original atoms in the condensate seem to have vanished in that they are not seen in either the remnant or the expanding gas cloud.
    Fascinating. Where could they have gone?

    This happens all the time in day to day life. Atoms are forever being pulverized into, electrons their basic composition.

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    William McCormick
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  7. #6  
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    Quote Originally Posted by Bunbury
    About half the original atoms in the condensate seem to have vanished in that they are not seen in either the remnant or the expanding gas cloud.
    Fascinating. Where could they have gone?
    In this I suspect McCormick is roughly correct. Those atoms passed into the depths.

    Here're lyrics to a bossa nova classic, The Girl From Ipanema. Remember those atoms in this mood. They're not gone, really, just different, and out of reach.

    Tall and tan and young and lovely, the girl from Ipanema goes walking
    And when she passes, each one she passes goes - ah
    When she walks, she's like a samba that swings so cool and sways so gently
    That when she passes, each one she passes goes - aah
    Ooh But he watches so sadly, How can he tell her he loves her,
    Yes he would give his heart gladly,
    but instead when she walks to the sea,
    she looks straight ahead not at him,
    Tall, and tan, and young, and lovely, the girl from Ipanema goes walking
    And when she passes, he smiles - but she doesn't see
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  8. #7  
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    Quote Originally Posted by KALSTER
    They think maybe into molecules that the detector can't detect, but still, as you say, fascinating! And even cooler: Current theory can’t explain it.
    Molecules being larger than their constituent atoms, you might think they should be easier to detect than atoms. :?
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  9. #8  
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    Quote Originally Posted by Bunbury
    Quote Originally Posted by KALSTER
    They think maybe into molecules that the detector can't detect, but still, as you say, fascinating! And even cooler: Current theory can’t explain it.
    Molecules being larger than their constituent atoms, you might think they should be easier to detect than atoms. :?
    Yes I agree. I have no idea how they detect them though :? . Another possibility is that the atoms where accelerated out of the magnetic trap.

    From the NIST site:
    "The fate of the missing atoms is still an open question, but the researchers suspect that they wind up either accelerated so greatly that they escape the trap undetected, or perhaps form molecules that are invisible to the detection system."

    Some brainfood provided on another forum:

    Feshbach Resonances and the BEC-BCS crossover

    Some more in-depth explanations of the BEC-BCS Crossover (PDF)
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
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  10. #9  
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    It could also be possible that the attractive forces make the BEC dense enough so that it creates an intense gravitational field within itself (after all, a black hole does not gain mass before its critical point, it only becomes denser). This could grow to such an extent that a singularity is formed in the core, which then takes in 1/2 of the matter, subsequently sending it to another place. Only 1/2 is taken because of the exponential attraction, which causes a break in the consecutive matter attraction well, leaving the rest behind. This amount left behind no longer possesses the critical mass necessary to reside in such a small space, and therefore explodes outwards. Essentially it is like a weight pushing a spring down to a certain point, then suddenly the weight vanishing causing the spring to immediately return back to its state without the weight.

    Hahaha, well, its appears after googeling "black hole" and "bosenova" that many other people have the same idea that I have. I guess I am not that crazy after all. Mmmmm......

    http://wapedia.mobi/en/Talk:Bosenova
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