1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Issue about CPT

  1. Sep 26, 2008 #1
    What is wrong in this reasoning about CPT symmetries?

    Spatial inversion P preserves spin and inverses velocity. (See wikipedia,
    at http://en.wikipedia.org/wiki/P-symmetry )

    Motion or time inversion T inverses both spin and velocity (obvious, see also wikipedia,
    at http://en.wikipedia.org/wiki/T-symmetry ).

    Now, charge conjugation C preserves chirality. ( http://en.wikipedia.org/wiki/Charge_conjugation )
    That means that either spin and velocity are both inverted or they are both preserved.

    But: In either of these two cases, C cannot be equal to TP.
    Now, C=TP is a deep theorem in physics!
    What is wrong in this argument chain?

  2. jcsd
  3. Sep 26, 2008 #2
    Nobody really says that C=PT, not in the sense that you get identical results from applying these two symmetries.

    In a classical world, C, P, and T are all symmetries by themselves. Meaning, you can take a physical process or an area of spacetime and apply C or P or T and you get a new valid process.

    In a quantum world, P is not a symmetry, because it takes valid weak-interaction processes into invalid processes. It is maximally violated by the weak interaction. CP is a lot better. The CPT theorem essentially states that you can take any valid process, apply C, P, and T (reverse spins and replace all particles with antiparticles), and you ALWAYS get a valid process.
  4. Sep 27, 2008 #3
    Oh, I understand. I have read so often that CP and T are either both broken or both
    conserved that I thought that this means that CP equals T. Ok, that is wrong.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Issue about CPT
  1. CPT Symmetry (Replies: 3)

  2. Confinement Issues (Replies: 2)