• 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.


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


(propose a free ad)

Site Statistics

205 submissions , 163 unreviewed
5,079 questions , 2,229 unanswered
5,348 answers , 22,758 comments
1,470 users with positive rep
819 active unimported users
More ...

  Strong CP Problem

+ 6 like - 0 dislike

So, as far as I know, the Strong CP Problem in QCD results from the theta angle term in the action: $i\theta\int_X F_\nabla\wedge F_\nabla$ where $\nabla$ is the gauge connection and $X$ is a manifold on which the theory is defined. This term obviously breaks CP symmetry with non-zero choice of theta angle. Correct me if I am wrong.

At any rate, experimental evidence has shown CP symmetry to be a consistent aspect of QCD, and the Strong CP Problem is essentially to discover CP violation or to prove CP symmetry in the lagrangian. Now, I am wondering about the particulars of various solutions to the problem. In particular, is it necessary to fabricate a new particle such as the axion, or are there (hypothetically) simpler and more easily verifiable ways of solving the problem?

Also, how important is the problem? In other words, would making experiment and theory consistent warrant a Nobel Prize? Or is it simply an irritating discrepancy that is not fundamentally important to our understanding of the Standard Model?

This post imported from StackExchange Physics at 2014-11-28 11:30 (UTC), posted by SE-user ciao
asked Nov 27, 2014 in Theoretical Physics by ciao (30 points) [ no revision ]

I was about to ask a similar 1st question... the CKM model doesn't explain all the experimental outcomes, particularly for charm/anticharm. CKM is already complex, thus a sample patch is not expected to handle the phenomena. Recent papers, background and links Observation of CP violation in charm decays .More data will help...

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:
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