Cosmological Constant Problem: Pre-Req Knowledge for Paper

In summary, the professor wants me to read through a paper that I don't understand and I need GR to understand it.
  • #1
Junaid456
5
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My professor wants to give me (and another kid) a problem in quantum cosmology. To that end, he asked me to read through his recent paper that appeared in the Physical Review Letters. He said that I should be able to go through it since all the paper employs is (quantum) scalar field theory, which you have been doing as part of your studying QFT in the summer.

I, however, upon looking at the paper am clearly stmped as I can't make a word out of it. To me, it seems heavy on GR and a lot of other stuff I haven't done.

Please let me know what do you think is the average amount of pre-requsite knowldge to go through the paper. I think my professor seemed to have rushed into giving me this paper:

ArXiv link: http://arxiv.org/pdf/1508.07664v2.pdf

PRL link: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061302

Thanks!
 
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  • #2
Junaid456 said:
To me, it seems heavy on GR

It does look to me like background in GR would be needed to follow this paper. Specifically, you would need to at least have some exposure to the Einstein Field Equation, the physical meaning of the stress-energy tensor, the meaning of isometries and Killing vector fields, and the ADM formalism. Any GR course or textbook will cover the first three (in fact Sean Carroll's online lecture notes, which are free, cover them). The last item might not be covered in all sources; it's covered in MTW, but MTW is very comprehensive. (I can't remember offhand how much it is covered in Wald.)
 
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Likes vanhees71
  • #3
Well, my two cents: I think your professor had a wrong judgement. You definitely need GR to understand that paper.
 
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Likes vanhees71
  • #4
Well, I'd address the professor again and ask him about sources, from where to learn the needed background. The length restriction of PRL doesn't make these papers easy to follow for the non-expert anyway (although it's most probably very interesting and high-quality research given that it's published in PRL). So I'd ask for additional background material and/or help with questions.
 
  • #5
I don't think he means that no GR is needed. He is only talking about the prerequisites from QFT. You need only scalar field theory and nothing more complicated from QFT. The GR is probably understood, or he assumes that you know some say you've taken a course.
 

1. What is the cosmological constant problem?

The cosmological constant problem is a major issue in modern cosmology that arises from the discrepancy between the predicted value of the cosmological constant, a term in Einstein's equations of general relativity that describes the energy density of empty space, and the observed value. The predicted value is estimated to be 120 orders of magnitude greater than the observed value, leading to the question of why the cosmological constant is so small.

2. What is the significance of the cosmological constant in our understanding of the universe?

The cosmological constant is important because it has a significant impact on the expansion rate of the universe. It is responsible for the accelerated expansion of the universe, which was first observed in the late 1990s and led to the discovery of dark energy. The value of the cosmological constant also affects the overall geometry of the universe and its ultimate fate.

3. What are some proposed solutions to the cosmological constant problem?

There are several proposed solutions to the cosmological constant problem, but none have been universally accepted. Some theories suggest that the observed value may be a result of the cancellation of different contributions to the cosmological constant, while others propose modifications to general relativity or introduce new particles or fields that could explain the small value of the cosmological constant.

4. How does the cosmological constant problem relate to other unanswered questions in cosmology?

The cosmological constant problem is closely linked to other unanswered questions in cosmology, such as the nature of dark energy and the ultimate fate of the universe. It is also connected to the problem of vacuum energy, which refers to the energy associated with empty space and is thought to play a role in the cosmological constant.

5. What is the current state of research on the cosmological constant problem?

The cosmological constant problem remains an active area of research in cosmology, and scientists continue to explore potential solutions and new theories to explain the observed discrepancy. Advances in observational techniques and technology, such as precision measurements of the cosmic microwave background radiation, may provide new insights into the nature of the cosmological constant and help resolve this long-standing problem.

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