4 ms·

The Superfluid Universe

33 points by bootload 11y ago

tfgg 11y ago
This is a pretty amazing and compelling idea, it feels odd that no one has thought of it before - the article mentions some previous models, what were they?
- selimthegrim 11y ago
  How this article failed to mention Grisha Volovik at all is beyond me. He is be far the most prominent proponent of this school of thought who isn't a cosmologist. The obvious problem with all these models is that the condensed matter theories don't obviously require Lorentz invariance. http://www.amazon.com/Universe-Droplet-International-Monographs-Physics/dp/0199564841 http://www.amazon.com/Universe-Droplet-International-Monogra...
  - selimthegrim 11y ago
    raattgift's comments earlier are almost certainly more correct than mine. I didn't read Khoury's paper throughly. My apologies.
- raattgift 11y ago
  The article is about In http://arxiv.org/abs/1507.01019 http://arxiv.org/abs/1507.01019 which has a long list of references.
donlzx 11y ago
How's it compared to superfluid vacuum theory? https://en.wikipedia.org/wiki/Superfluid_vacuum_theory https://en.wikipedia.org/wiki/Superfluid_vacuum_theory
- contravariant 11y ago
  This theory requires the 'dark matter' to be in its superfluid phase in galaxies, but in a different phase outside. Also, an important difference between dark matter and empty space is that the expansion of the universe doesn't generate more dark matter but does generate more space. This is what distinguishes dark matter from dark energy.
- raattgift 11y ago
  They're pretty much entirely unrelated. In http://arxiv.org/abs/1507.01019 http://arxiv.org/abs/1507.01019 the authors lean on research into axions as extensions to the Standard Model and on Bose Einstein Condensate research in ordinary matter, and proposes a temperature (~ 1 mK) below which the light axion-like gas condenses into a superfluid. It's firmly rooted in General Relativity and is proposed as an ordinary matter field in the GR sense. The field content feels and generates curvature just like all the fields in the Standard Model. Its non-removable vacuum background is the standard four-dimensional smooth connected Lorentzian manifold. Superfluid vacuum theory (SVT) is a family of emergent gravity theories that aims to replace General Relativity by proposing that a superfluid with lattice spacing at Planck scale is part of the non-removable background and the dynamics of gravitation take place in the superfluid. At low temperatures, and at low particle energies, the superfluid reproduces GR. This approach to emergent gravity was tried with non-superfluid fluids historically, and those attempts failed in the face of detailed study of objects in our sky that are bright in extreme UV and higher frequencies. Emergent gravity theories tend to get more complicated (e.g., SVT theories have variously introduced mechanisms to suppress dissipation effects, and introduced rotation and/or phase transitions in the background superfluid) when they have to match recent successes of General Relativity. When you have to keep making substantial changes to your theory to match observables predicted using GR a century ago, it's a bad sign.
  - deleted 11y ago
    [deleted]
effie 11y ago
> First predicted in 1924 by Einstein and the Indian physicist Satyendra Bose, this whole class of ultra-cold superfluids is now known as Bose-Einstein condensates. No, this whole class of ultra-cold superfluids (referring to fluids similar to superfluid helium) were not "first predicted in 1924", as Mrs. Hosenfelder erroneously writes. It is the Bose-Einstein condensate (BEC) that was predicted in 1924, not superfluids. A Bose–Einstein condensate is a state of matter where dilute gas of weakly interacting bosons of cold enough temperature turns into condensate, a different phase of matter. A superfluid was first discovered in liquid helium in 1937-1938 experimentally by Kapitza and independently by Allen and Misener. Liquid helium is no weakly interacting gas, but nevertheless the explanation of its superfluidity in terms of Bose-Einstein condensate was proposed soon after the discovery. Later on it turned out that superfluid helium is no ordinary BEC, but needs quite a different description (interacting particles in liquid). As Balibar writes, "65 years later, the connection between superfluidity and BEC is still a matter of debate and study" https://www.researchgate.net/publication/1935151_Looking_back_at_superfluid_helium https://www.researchgate.net/publication/1935151_Looking_bac... See also https://www.eng.fsu.edu/~dommelen/quantum/style_a/nt_sfnebec.html https://www.eng.fsu.edu/~dommelen/quantum/style_a/nt_sfnebec... https://www.physicsforums.com/threads/superfluidity-helium-3-and-helium-4.640281/#post-4097603 https://www.physicsforums.com/threads/superfluidity-helium-3... There are also other superfluids that are not BEC, like superfluid helium 3. It is fermionic condensate, not BEC. I remember from my studies of physics that all this was quite a common knowledge in the circles of cold temp physics. I wonder why Mrs. Hossenfelder, a physicist herself, neglects to reflect this basic knowledge in her article. Perhaps she is now more of a pop-sci blogger than a scientist?
effie 11y ago
> "It is impossible to be interested in cosmology today without being interested in dark matter", says Stefano Liberati Mr. Liberati seems to think dark matter is as real and proven as the air we breathe, but forgot that so far it is only one of ideas proposed to explain the speeds of visible bodies. I am sure one can study other ideas that do not depend on the concept of electromagnetically passive matter at all, like different gravity formula or EM mechanisms. Perhaps he meant to say it is impossible to get a grant or get attention without being interested in dark matter, or something like that...

33 points by bootload 11y ago

tfgg 11y ago

This is a pretty amazing and compelling idea, it feels odd that no one has thought of it before - the article mentions some previous models, what were they?

selimthegrim 11y ago
How this article failed to mention Grisha Volovik at all is beyond me. He is be far the most prominent proponent of this school of thought who isn't a cosmologist. The obvious problem with all these models is that the condensed matter theories don't obviously require Lorentz invariance. http://www.amazon.com/Universe-Droplet-International-Monographs-Physics/dp/0199564841 http://www.amazon.com/Universe-Droplet-International-Monogra...
- selimthegrim 11y ago
  raattgift's comments earlier are almost certainly more correct than mine. I didn't read Khoury's paper throughly. My apologies.
raattgift 11y ago
The article is about In http://arxiv.org/abs/1507.01019 http://arxiv.org/abs/1507.01019 which has a long list of references.

donlzx 11y ago

How's it compared to superfluid vacuum theory? https://en.wikipedia.org/wiki/Superfluid_vacuum_theory https://en.wikipedia.org/wiki/Superfluid_vacuum_theory

contravariant 11y ago
This theory requires the 'dark matter' to be in its superfluid phase in galaxies, but in a different phase outside. Also, an important difference between dark matter and empty space is that the expansion of the universe doesn't generate more dark matter but does generate more space. This is what distinguishes dark matter from dark energy.
raattgift 11y ago
They're pretty much entirely unrelated. In http://arxiv.org/abs/1507.01019 http://arxiv.org/abs/1507.01019 the authors lean on research into axions as extensions to the Standard Model and on Bose Einstein Condensate research in ordinary matter, and proposes a temperature (~ 1 mK) below which the light axion-like gas condenses into a superfluid. It's firmly rooted in General Relativity and is proposed as an ordinary matter field in the GR sense. The field content feels and generates curvature just like all the fields in the Standard Model. Its non-removable vacuum background is the standard four-dimensional smooth connected Lorentzian manifold. Superfluid vacuum theory (SVT) is a family of emergent gravity theories that aims to replace General Relativity by proposing that a superfluid with lattice spacing at Planck scale is part of the non-removable background and the dynamics of gravitation take place in the superfluid. At low temperatures, and at low particle energies, the superfluid reproduces GR. This approach to emergent gravity was tried with non-superfluid fluids historically, and those attempts failed in the face of detailed study of objects in our sky that are bright in extreme UV and higher frequencies. Emergent gravity theories tend to get more complicated (e.g., SVT theories have variously introduced mechanisms to suppress dissipation effects, and introduced rotation and/or phase transitions in the background superfluid) when they have to match recent successes of General Relativity. When you have to keep making substantial changes to your theory to match observables predicted using GR a century ago, it's a bad sign.
- deleted 11y ago
  [deleted]

effie 11y ago

> First predicted in 1924 by Einstein and the Indian physicist Satyendra Bose, this whole class of ultra-cold superfluids is now known as Bose-Einstein condensates. No, this whole class of ultra-cold superfluids (referring to fluids similar to superfluid helium) were not "first predicted in 1924", as Mrs. Hosenfelder erroneously writes. It is the Bose-Einstein condensate (BEC) that was predicted in 1924, not superfluids. A Bose–Einstein condensate is a state of matter where dilute gas of weakly interacting bosons of cold enough temperature turns into condensate, a different phase of matter. A superfluid was first discovered in liquid helium in 1937-1938 experimentally by Kapitza and independently by Allen and Misener. Liquid helium is no weakly interacting gas, but nevertheless the explanation of its superfluidity in terms of Bose-Einstein condensate was proposed soon after the discovery. Later on it turned out that superfluid helium is no ordinary BEC, but needs quite a different description (interacting particles in liquid). As Balibar writes, "65 years later, the connection between superfluidity and BEC is still a matter of debate and study" https://www.researchgate.net/publication/1935151_Looking_back_at_superfluid_helium https://www.researchgate.net/publication/1935151_Looking_bac... See also https://www.eng.fsu.edu/~dommelen/quantum/style_a/nt_sfnebec.html https://www.eng.fsu.edu/~dommelen/quantum/style_a/nt_sfnebec... https://www.physicsforums.com/threads/superfluidity-helium-3-and-helium-4.640281/#post-4097603 https://www.physicsforums.com/threads/superfluidity-helium-3... There are also other superfluids that are not BEC, like superfluid helium 3. It is fermionic condensate, not BEC. I remember from my studies of physics that all this was quite a common knowledge in the circles of cold temp physics. I wonder why Mrs. Hossenfelder, a physicist herself, neglects to reflect this basic knowledge in her article. Perhaps she is now more of a pop-sci blogger than a scientist?

effie 11y ago

> "It is impossible to be interested in cosmology today without being interested in dark matter", says Stefano Liberati Mr. Liberati seems to think dark matter is as real and proven as the air we breathe, but forgot that so far it is only one of ideas proposed to explain the speeds of visible bodies. I am sure one can study other ideas that do not depend on the concept of electromagnetically passive matter at all, like different gravity formula or EM mechanisms. Perhaps he meant to say it is impossible to get a grant or get attention without being interested in dark matter, or something like that...