Arcadian Functor

occasional meanderings in physics' brave new world

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Marni D. Sheppeard

Sunday, August 02, 2009

The Imperial Force

If you missed the recent London debate between the Dark Side proponent, Andrew Jaffe, and sensible theorist, Subir Sarkar, there is an Imperial podcast available. I also enjoyed the review on the Physics World blog:
Sarkar was second to take the stage and he put forward a very different view. He immediately urged us - along with all working cosmologists - to abandon this “ridiculous” notion of a mysterious repulsive fluid that allegedly fills 75% of the universe.
The waning power of the Dark Force was in evidence at the debate, with onlookers asked to vote on whether or not they thought DE existed. As Physics World reports:
Despite this being just a bit of fun, it was still interesting to see Sarkar sweep to victory by such a significant margin.


Anonymous Rude and Inconsiderate said...

Some of us egotists don't exactly disagree with the idea that 75% of the energy of the universe behaves as a repulsive fluid. Beware of bias, Marni.

August 02, 2009 9:13 AM  
Blogger Kea said...

Dear anonymous coward. Wow, you're a bright spark, aren't you? It's the job of a theoretical physicist to be biased ... by the DATA ... which now indicates that the repulsive fluid idea is wrong. That's right, wrong. Who cares what egotists, or non egotists, think. Only the data, and good ideas, count.

August 02, 2009 8:50 PM  
Blogger Kea said...

Andrew Jaffe has a new post.

August 02, 2009 9:15 PM  
Anonymous Anonymous said...

Thanks for the link, but Jaffe's post is in favour of dark energy! What flawed data "indicates that dark energy is wrong"?

If you object to both non-anonymous comments (which you claim egotistical) and anonymous comments (which you claim cowardly), you're just inventing reasons to object to anything.

August 02, 2009 9:43 PM  
Blogger Kea said...

To begin with, watch and digest this. Then look at Riofrio's old graphs and blog posts ... carefully.

To clarify: it is clear that the Dark Force might work OK as an effective description, and is certainly needed if one wishes to apply GR on cosmological scales. But any proponent of a truly quantum cosmology cannot be happy with the application of old physical ideas (and that includes the graviton exchange picture) to such astounding data.

August 02, 2009 10:13 PM  
Anonymous Anonymous said...

The experimental data do not disfavor dark energy. Ms. Sheppeard is basically just a crackpot who is against any mainstream idea. In her universe, dark energy, the Higgs mechanism, and supersymmetry are all just frauds imposed by the 'imperial' powers to suppress truth-seekers like her. Please, give me a break.

August 03, 2009 5:10 AM  
Anonymous kneemo said...

Without a complete theory of quantum gravity, it's difficult to address the problem of observed accelerated expansion. If one assumes that M-theory and its low energy limit, supergravity, are good approximations to a final theory of quantum gravity, its possible to make some educated guesses, however.

Back at ICGTMP 26, Ramzi Khuri discussed his simple model, where repulsive velocity-dependent interactions of moving extremal Reissner-Nordstrom black holes result in an accelerating, expanding universe. Such results also hold generally, whenever the velocity-dependent Lagrangian takes the form L=1/2(mv^2)(1+f(r)v^2), (f(r) being a monotonically decreasing function of separation r), as in the case of supersymmetric strings and branes.

Charged, extremal black holes arise naturally, in compactifications of D=11 supergravity down to D=4, and should have observable effects in our universe, if M-theory is accurate. Whether one refers to such effects as "dark energy" or "repulsive fluid", is quite harmless given our early theoretical understanding of the subject.

August 03, 2009 1:01 PM  
Blogger Kea said...

Hi kneemo. M theory black holes certainly provide us with valuable insights, but I disagree that labelling everything 'dark energy' is not harmful. The Dark Force does not explain anything. I prefer Louise's clear, predictive words from 2003/2004: ...but normal Gaussian distribution predicts that 68% of mass will lie in regions of overdensity. Such regions will have collapsed into singularities, appearing as great voids between sheets of galaxies. The missing 68% of the Universe ascribed to Dark Energy may be hidden within those voids.

August 03, 2009 7:51 PM  
Blogger BCooper108 said...

This comment has been removed by the author.

August 04, 2009 3:28 AM  
Blogger L. Riofrio said...

Bravo for this post! The anonymous cowards out there are getting desperate, along with the rest of the dark side.

August 04, 2009 3:30 AM  
Anonymous Stuffy said...

An open question... Kea (whoever she really is)
Einstein's Telescope: The Hunt for Dark Matter and Dark Energy in the Universe by Evalyn Gates

August 04, 2009 4:13 AM  
Blogger kneemo said...

... but I disagree that labelling everything 'dark energy' is not harmful. The Dark Force does not explain anything.

Yes, I agree it does not explain anything. My point was that the problem seems to require a mathematical understanding that is beyond even the top theorists. If anything, M-theorists should be actively engaged in this debate as the physics far transcends the framework of GR.

August 04, 2009 12:22 PM  

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