Can Quantum Gravity Explain Inflation After the Big Bang?

[friend]

I wonder if quantum gravity effects can explain Inflation after the Big Bang? For example, in Loop Quantum Gravity, there are area and volume operators and eigenvalues, etc. Would there be jumps from one volume state to another with time? Thanks.

 

[marcus]

I wonder if quantum gravity effects can explain Inflation after the Big Bang? For example, in Loop Quantum Gravity, there are area and volume operators and eigenvalues, etc. Would there be jumps from one volume state to another with time? Thanks.

There have been papers on both sides of this issue. As a sample, here is a list of 48 papers:
http://arXiv.org/cits/gr-qc/0403106

These are the papers that cited an early work on this by Bojowald et al.
http://arXiv.org/abs/gr-qc/0403106

My personal opinion is that a brief inflationary period does arise in LQC---and is robust or generic. But this naturally arising brief inflation is not enough to produce the "60 e-folds" typically desired for inflation scenarios.

It seems that something must be put in by hand, to get the expansion by the factor e⁶⁰ believed necessary to explain flatness and isotropy.

So what I see happening is that in recent LQC work by e.g. Ashtekar and Singh, they put in an inflaton field to get the conventional amount of inflation. The amount that is automatically occurring in the LQC models is not enough. This is just my personal view, I think opinions about it differ.
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A separate issue is whether, in LQC, you actually need e⁶⁰-fold inflation. The "horizon problem" doesn't exist in a nonsingular model with a bounce because temperature equilibrium can have been achieved prior to bounce. A major motivation for inflation scenarios, namely the CMB temperature isotropy puzzle, is no longer so pressing. Whether and how much inflation is needed remains unresolved, as far as I know.

 

[Entropia]

I understand the curiosity about the potential connection between quantum gravity and inflation after the Big Bang. However, it is important to note that the theory of inflation is still a subject of ongoing research and there is no consensus on its exact mechanism. While there have been some attempts to incorporate quantum gravity into inflationary models, there is currently no conclusive evidence that quantum gravity can fully explain inflation.

In Loop Quantum Gravity, the area and volume operators and their corresponding eigenvalues play a crucial role in understanding the quantum nature of space and time. However, it is not yet clear how these operators and their associated jumps in volume states could be connected to the rapid expansion of the universe during inflation.

Furthermore, the scale at which quantum gravity effects become significant is much smaller than the scale at which inflation is thought to have occurred. This makes it difficult to directly apply the principles of quantum gravity to explain inflation.

In summary, while the connection between quantum gravity and inflation is an intriguing topic, there is still much research to be done before we can fully understand and explain the origins of inflation after the Big Bang.