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BEC and RELATIVITY

  1. Dec 9, 2005 #1
    From a few days I was thinking that the fifth state of matter Bose-Einstein Condensate will obey the rules of Relativity!
    ...if practicals have been done on that please, tell me the results that were found.:confused:
     
  2. jcsd
  3. Dec 9, 2005 #2
    can u please give a hint how relativity in BEC?
     
  4. Dec 11, 2005 #3
    Actually, in the discussion of "Underlying the cause of inertia" on the forum of Physics somewhere, it was being arisen that the cause of inertia may be the energy or the unstable particles possessed by ther matter which are charged or energised.

    Now, BEC doesn't possess any energy ( having zero kelvin temperature ) and I think that BEC is the most stable ( the absolute rest predicted by Isaac Newton ). If it doesn't have any energy so it mustn't follow the laws of gravitation, inertia, and relativity and much more...

    if, there is any misconfusion please clarify me.
     
  5. Dec 11, 2005 #4

    ZapperZ

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    This is wrong.

    1. You should never use the internet, even PF, as your primary source of info.

    2. BEC doesn't just occur at 0K. If it does, we'd never have one. He4 condenses close to 4K. Superconductivity, which forms composite bosons and condenses into a BE state, can form at temperature as high as 130K.

    3. You need to look at the theory and discovery of BE condensate (not just what is on here) and see where exactly "relativity" comes in if you want to make these kinds of assertion.

    Zz.
     
  6. Dec 31, 2005 #5
    What else is there?
     
  7. Dec 31, 2005 #6

    Dr Transport

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    Publications in well respected journals is always your first source of creditable information about a subject.... The internet is full of material that is just plain wrong, written by crack-pots who haven't a clue and can't be held accountable for their rantings.
     
  8. Dec 31, 2005 #7
    What??

    Unless Carl Weiman was wrong about his own nobel prize winning experiment when he lectured me, then even 1/10,000 of a degree above 0K does not produce BEC. Now, I forget how close they got to absolute zero, but something around 10^-12K. So, yes, we did have BEC because we got close enough to absolute zero.

    Superconductivity and BEC are two different things even though they both occur close to absolute zero.

    I also, to the topic creator, don't see where relativity comes in.
     
  9. Dec 31, 2005 #8

    ZapperZ

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    You are confusing atomic BEC gas, which is what Weiman won the Nobel Prize for, with BEC in GENERAL! Don't believe me? Look at liquid He4. The superfludity of He4 is due to a BE condensation.

    And we know that BCS and BEC are NOT that different after all after the recent discovery of fermionic condensate (or did you miss the story completely even though it was discover at JILA?). It is a smooth crossover between the two.

    I also wouldn't call Tc=100K as "close to absolute zero".

    Zz.
     
  10. Dec 31, 2005 #9
    Yeah, superfluidity is a special case.

    BCS and BEC are similar, but not the same and with so much yet to be understood about both of them then we should be careful with too many assumptions about their similarity. Dan Dessau, who works on BCS with the JILA group made sure that we understood this during a lecture he did, and I'll be honest that quite a lot was too dense because I haven't gotten into quantum mechanics yet so I didn't really understand it. Anyway, he talked about how He3 superfluidity and He4 superfluidity would be different though they are both special forms of condensed matter, and so how BEC and BCS could have many differences too. I don't really know much about this stuff, so I'm not trying to argue, and if you knew more then I'd want to hear it out of interest.

    I was just surprised how you said we'd never have BEC since it occurs at absolute zero, and clearly we got close enough.
     
    Last edited: Dec 31, 2005
  11. Dec 31, 2005 #10
    Oh yeah, and I'm still confused what this topic was orginally talking about with relativity.
     
  12. Dec 31, 2005 #11

    ZapperZ

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    Whaaaaa????

    Where did I say that? In fact, I clearly said:

    You need to read a little bit more carefully. I cannot defend something I never claim.

    And I know Dan Dessau pretty well. I came out of photoemission spectroscopy of high-Tc superconductors, something he did when he was at Stanford and continues today at Colorado. He4 and He3 both creates BE condensation when they form superfluids, but the mechanisms are different! The formation of cooper pairs in superconductors also can form BE condensation of these composite bosons. Again, the mechanism is different. But they are all GENERICALLY BE condensates.

    Zz.
     
  13. Dec 31, 2005 #12
    Hmm, okay, I thought you were claiming we haven't gotten to absolute zero. The way I understand it, since it is a statistic that if 100% of the atoms are grounded then that should be absolute zero, so 0K is definitely possible and I thought it had been done with Wieman and others since.

    Right, the electrons form Cooper pairs, which are generically BE condensate, but still different from absolute zero BEC.

    That's cool you Dan though. He's a really good prof.
     
  14. Dec 31, 2005 #13
    No group has ever achieved absolute zero.

    Just because the atoms are in the ground state does not mean they are at absolute zero.
     
  15. Jan 1, 2006 #14
    I don't really understand how they measure the temperature anyway. Because it is a Bose statistic, and if all the atoms are in the ground state then why wouldn't it be absolute zero?
     
  16. Jan 10, 2006 #15

    Gokul43201

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    Mostly, the temperature is calculated from some other measured property of the condensate. Typically, the temperature is estimated by fitting a Gaussian to the atomic cloud or from the envelope of collective oscillations.
    How do you get all the atoms to be in the ground state ? Recall that the BE phase transition is defined as the appearance of a macroscopic order parameter (ground state occupancy). This only requires that there be a "large" number of particles in the ground state - not all of them.
     
  17. Feb 26, 2006 #16
    First of all it's not possible to achieve 0K according to the Third Law of Thermodynamics, which says that 0K will ONLY occur when all of the matter AND energy is randomly distributed across the universe. Which is basically saying it is impossible to achieve this state. "it is impossible to cool a body to absolute zero by any finite process. Although one can approach absolute zero as closely as one desires, one cannot actually reach this limit" check out http://www.infoplease.com/ce6/sci/A0861526.html
     
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