Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Can the findings of the Physics Nobel Laureates of 2011, namely the overpowering existence of dark energy (vacuum energy) have any implications in the quest the combine Quantum Mechanics and General Relativity? Maybe toward a theory of Quantum Gravitation?

share|improve this question
3  
If anybody had done this successfully, chances are we would have heard about it. We haven't, but I don't know of be reason why it's impossible. So I would have to say that nobody knows. –  Peter Shor Dec 10 '11 at 20:03
add comment

2 Answers

YES. The cosmological constant is extremely fine tuned. In a nonsupersymmetric world, bosons contribute enormous zero-point energies to the cosmological constant while fermions contribute an enormous negative amount. For both contributions to cancel in one part in 10 to the 123 is nothing short of miraculous. No other mechanism than unbroken symmetry appears to explain such fine-tuning needed for the evolution of life. Increase the cosmological constant by a few orders of magnitude and sufficient structure formation of galaxies and stars won't happen.

This points to the anthropic principle giving a special role to consciousness and needs a multiverse of pocket universes with different laws of physics. This fits in very nicely with the landscape of compactifications in string theory, and the theory of eternal inflation.

In string theory, any vacuum with a positive cosmological constant has to be metastable, and if so, our phase will have to decay to a more stable vacuum in the future.

As long as we remain in our current phase, the maximum entropy of our causal patch of the universe is bounded by the holographic bound of 10 to the 123.

share|improve this answer
add comment

Dark energy certainly can have implications for unifying QM and GR, in the sense that if we do develop a proper theory of quantum gravity, it should (probably) explain dark energy along with everything else. So any candidate theory that does give the correct density for dark energy becomes much more appealing than one that does not. So in this sense we can use dark energy as a "filter" for candidate QG theories.

However, I doubt that the knowledge of dark energy can lead directly to a quantum theory of gravity. If that were possible without being too difficult, someone would probably have done it already, and as Peter Shor posted in a comment, we probably would have heard about it.

share|improve this answer
1  
I didn't say that if it were possible, it's likely that someone would have done it. I said that if somebody had done it, we would likely know. Thus, since nobody has done it, we can't tell whether it's possible (although I agree it is unlikely). –  Peter Shor Dec 11 '11 at 4:04
    
@Peter my mistake, sorry about that. I've edited to fix it. –  David Z Dec 11 '11 at 4:06
    
What about us living in de Sitter space rather than AdS? I wouldn't be surprised if string theorists argued that ST predicts AdS if we didn't have the observed dark energy. –  JollyJoker Jan 10 '12 at 5:41
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.