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Are Bose-Einstein condensates affected by gravitational attraction? In sufficient quantity, do Bose-Einstein condensates exert a gravitational force?

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    $\begingroup$ Any form of energy contributes to gravity, in a way that is determined quantitatively by general relativity. $\endgroup$
    – Danu
    May 5, 2014 at 15:25

2 Answers 2

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Yes, Bose-Einstein condensates are affected by gravity. Most condensates are formed in laser traps and often (especially in the early experiments) the lasers must be turned off to get a good image of the condensate, with the consequence that many images of condensates (again, especially from the early experiments) show them falling.

An example (source):

falling BEC

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Atomic condensates are subjected to gravity as every massive particle is. What do you mean by 'in sufficient quantity'? In any theoretical treatment of a BEC I know of gravity is not taken into considerations as obviously the effects on the dynamics to the atomic level are negligible. However, yes, there is always a gravitational attraction between the atoms of the condensate. The answer to the question 'does an atomic BEC exert gravitational attraction on other massive objects' is still the same: yes it does as it is massive.

Recently researchers claimed they obtained a photon condensate. In that case gravitational forces wouldn't be present as photons are massless.

To go even further, if the graviton was found to exist, it may form a BEC as it is predicted to be a spin-2 particle (ergo a boson). Speculations on graviton BEC exist related to black holes physics.

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    $\begingroup$ I think you are wrong saying that the light does NOT gravitate... I hope experts can add something. $\endgroup$
    – Py-ser
    Aug 5, 2014 at 7:11
  • $\begingroup$ The whole point of my answer (which is also the reason why rob's is not relevant) is that 1) the question is not well posed, 2) gravity does of course act on the condensed atoms as they are massive but plays no role in the dynamics of the condensation. $\endgroup$
    – Semola
    Aug 5, 2014 at 12:34
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    $\begingroup$ If gravity is bending of space-time, and photon's energy contribute to the tensor, then they influence gravity. This is my impression, but again I am not an expert. Also, probably this is off-topic, but I was curious :) $\endgroup$
    – Py-ser
    Aug 6, 2014 at 0:18
  • $\begingroup$ @LucaMingarelli: light has a nonzero stress-energy tensor, and therefore, a nonzero gravitational field. $\endgroup$ Oct 15, 2014 at 20:00
  • $\begingroup$ For instance, it is pretty trivial to create a recollapsing cosmology containing only radiation. $\endgroup$ Oct 15, 2014 at 20:01

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