Quantcast
  • Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.

News

PO is now at the Physics Department of Bielefeld University!

New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback

Attributions

(propose a free ad)

Site Statistics

205 submissions , 163 unreviewed
5,047 questions , 2,200 unanswered
5,345 answers , 22,709 comments
1,470 users with positive rep
816 active unimported users
More ...

  Quantum gravity: How can the microscopic degrees of freedom of space-time be determined?

+ 1 like - 0 dislike
453 views

Researchers in quantum gravity seem to agree that space-time is emergent: it is made of many microscopic degrees of freedom, most probably of Planck size. Google Scholar lists many proposals: loops, chain mail, strings, trinions, twistors, causal sets, to name just a few. It seems that all these proposals are interesting and most of them yield general relativity in some suitable limit. 

So far, there seems to be no consensus.  But many researchers work on their own model since 20 or 30 years. How do they know that they are working on the best model? Or on the correct model?  

How can or could an outsider determine which of these proposals is correct? What is the best way to compare the proposals against each other? In the end, the question is this: What is the best criterium to find out what space-time is made of?

asked Dec 18, 2022 in Chat by Michael [ no revision ]
recategorized Dec 18, 2022 by Arnold Neumaier

So far none is proved correct; what is promising depends on who judges. To form an opinion on what is promising one must study them all or wait till there is agreement. People work on one or two of the options hoping to illuminate their consequences so that one can possibly decide in the future what has a chance to succeed.

Well, in physics "waiting til there is agreement" is not the way to do research. We look for arguments, not for agreement. The question is about which arguments should be used - not about which authorities we should follow.

Different authorities suggest following different lines of argument. Thats how science proceeds when there is no agreement.

The question was precisely about the arguments / criteria! What are they?

Your question asks far too many questions simultaneously.

All researcher favor their own arguments and criteria. The criteria are vague and the argument convince only their supporters. otherwise there would be agreement. Don't expect to get a list of all the many possibilities!

1 Answer

+ 0 like - 0 dislike

Your question was:

           What is the best criterium to find out what space-time is made of?

There is only one criterion in physics: correspondence with observations.

Every theory of quantum gravity needs to reproduce general relativity in the classical limit.

And every theory of quantum gravity has to reproduce quantum theory and particle physics.

At present, no theory fulfils the last criterium: no theory explains elementary particles and gauge interactions. So, at present, the answer is simple: no theory agrees with observation. 

answered Jan 14, 2023 by Butterfly [ no revision ]

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
p$\hbar$ysicsOv$\varnothing$rflow
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
Please complete the anti-spam verification




user contributions licensed under cc by-sa 3.0 with attribution required

Your rights
...