Quantum Gravity Theory and Interpretations of QM

[Curious6]

I was wondering once a consistent quantum gravity theory would be devised (I have in mind especially string theory or loop quantum gravity) what would happen to quantum mechanics interpretations. Would these all be abandoned? Would a new interpretation come up? I mean by this for example, would a quantum gravity theory disprove the Copenhagen Interpretation or Many Worlds? Is there any relationship?

 

[marlon]

I think not (though i don't think we can be sure) since LQG uses the elements of QM.

Besides whatever the outcome may be, we will never abandon the concept of QM since it describes the atomic behaviour very accurately.

We didn't abandon Newtonian physiscs once GTR was constructed, right ?
We just talk about regimes in that case, where is a theory valid and where is it not.

regards
marlon

 

[marcus]

I think not (though i don't think we can be sure) since LQG uses the elements of QM.

Besides whatever the outcome may be, we will never abandon the concept of QM since it describes the atomic behaviour very accurately.

We didn't abandon Newtonian physiscs once GTR was constructed, right ?
We just talk about regimes in that case, where is a theory valid and where is it not.

regards
marlon

I agree with each point Marlon makes here. quantizing gravity is more a matter of confirming QM by extending it to cover more physics, and it may even involve some improvements in QM---making it work for gravity too.

It is always possible that extending quantum theory to cover the geometry of spacetime will trigger a revolution in the concepts of QM and bring people to a new interpretation of it, and John Baez has speculated about this possibility recently in a philosophical essay called Quantum Quandaries.
I will get a link for it. I am not recommending this point of view since I basically agree with Marlon that it looks like LQG is quantizing a classical theory in a more or less usual way (sorry guys, no revolution this time!).
But we should also take account of different opinions like in Baez essay.

 

[sol2]

I will have to look at what John saids, Marcus.

I agree with Marlon as well.

The fact is the geometricizatin of quantum gravity needs to answer how QM will evolve. That is what all the fun is about between LQG and STrings and those who had modified," Three Roads to Quantum Gravity".

A lot of also know that GR has to evolve too. Bohr wanted this compromise( from my perspective, a man who rejects the work of another as infantile degrations [Bohr's example of Einstein sremaining thirty years of unproductiveness], screams the loudest about how one truly feels?) and so did Schrodinger. They must of thought Einstein to be a stubborn man? :rofl:

Many bright minds are working at it from different perspectives, curious6.

 

[marcus]

John Baez
Quantum Quandaries: A Category-Theoretic Perspective

discussion at SPR
https://www.physicsforums.com/showthread.php?t=18633&highlight=quandaries

To appear in a book called Structural Foundations of Quantum Gravity
eds. Steven French, Dean Rickles and Juha Saatsi, Oxford U. Press.

preprint:
http://www.arxiv.org/abs/quant-ph/0404040

exerpts from the abstract:

"General relativity may seem very different from quantum theory, but work
on quantum gravity has revealed a deep analogy between the two. ...We show how this accounts for many of the famously
puzzling features of quantum theory: the failure of local realism, the
impossibility of duplicating quantum information, and so on. We argue
that these features only seem puzzling when we try to treat Hilb as
analogous to Set rather than nCob, so that quantum theory will make
more sense when regarded as part of a theory of spacetime..."

he argues that since there are still things that puzzle people about QM it is possible that a better understanding of Quantum Theory itself could come out of quantum gravity. And he explores an analogy between GR and QM that shows up in taking a category-approach to each. why does QM use Hilbert space and why does GR use cobordisms (space time continua connecting one geometry to another) and what is in common between hilbertspaces and cobordisms as abstract categories

dont get the idea that I am advocating this, but it is a good balance to a more commonsense view.

 

[sol2]

Another interpretation that aligns with Smolins views is all You just have to understand the flavour this issue is given, and distinct tastes or smells, are very compelling if you know what your looking at.

One thing I would like to say is, I have found a deeper explanation philospohically that is governing Smolins thoughts on this approach, that help me understand the divergence and method by which he maintains LQG. Why Marcus possibly maintains it as well. I have gather together my thoughts here, as the idea here, is to capture that true essence.

https://www.physicsforums.com/showpost.php?p=308810&postcount=8

We must agree here that a philosophical idealism is emitted form both positions. I knowthis now of Smolin and now I knowthis O fJohn Baez. This does not limit my perceptions and endeavors on their approach, but I listen attentively, to how their perspectives have been formed.

 

[Demystifier]

In
http://arxiv.org/abs/hep-th/0407228
http://arxiv.org/abs/hep-th/0601027
I suggest the following: If you require that QFT should be manifestly space-time covariant, then the Bohmian deterministic interpretation of quantum theory naturally emerges. In particular, a new formulation of quantum gravity that contains the Wheeler-DeWitt equation as a special case is derived.