# Questions tagged [cpt-symmetry]

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### What is relation between CPT invariance & Lorentz invariance, and why mass of particle/antiparticle is different in CPT violation?

(1) I read that CPT theorem can be proved with Lorentz invariance. Also, CPT violation implies Lorentz violation. Is CPT invariance equivalent with Lorentz invariance, or just one-side direction holds?...
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### Time-reversal transformation acts on the Dirac lagrangian with nonabelian gauge field

Time-reversal transformation acts on the Dirac lagrangian with (non)abelian gauge field Since earlier in Time-reversal transformation acts on the Weyl lagrangian with nonabelian gauge field, we ...
72 views

### Time-reversal transformation acts on the Weyl lagrangian with nonabelian gauge field

I would like to show time-reversal transformation acts on the Weyl lagrangian in the familiar 4 dimensional space-time. My notation follows the same as Peskin QFT book, such as that of chapter 3. I ...
1 vote
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### Regarding the action of Time reversal on Dirac spinors

I'm inquring about the difference between notions of time reversal found in Streater & Wightman's "PCT, Spin and Statistics, and All That", and this accepted answer from Chiral Anomaly. ...
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### Does the CPT theorem imply $CP=T$?

Does the CPT theorem imply $CP=T$? That is, does it imply that the action of Charge Conjugation and Parity inversion on some representation of the Lorentz group, is the same as doing a time reversal? ...
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### Help me understand the CPT signatures of different physical quantities

I am an engineer and not a trained physicist, but still I am fascinated by symmetries and I want to understand them. Specifically, in a paper ¹ I found the below table which covers a large number of ...
128 views

### Why is CPT symmetry necessary to prove the spin-statistics theorem?

I was reading the Wikipedia article on the spin-statistics theorem. It has a section going through a "suggestive bogus argument", where they rotate products of fields. To show why it doesn't ...
65 views

### Sign discrepancy in CPT theorem

I'm reading Fundamentals of Neutrino Physics and Astrophysics by Carlo Giunti and Chung W. Kim (2007). In chapter 2 section 11.5, they talk about the CPT theorem and how each fermion bilinear ...
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1 vote
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### $C$, $P$, $T$ symmetry of $O(3)$ non-linear sigma model

Consider the $O(3)$ nonlinear sigma model with topological theta term in 1+1 D: $$\mathcal{L}=|d\textbf{n}|^{2}+\frac{i\theta}{8\pi}\textbf{n}\cdot(d\textbf{n}\times d\textbf{n}).$$ The time reversal ...
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### Is CPT a unitary symmetry or an antiunitary symmetry?

Is CPT a unitary symmetry or an antiunitary symmetry, such as the free Dirac theory of fermion $\psi$ in Chapter 3 of Peskin's QFT book? Since T is antiunitary symmetry, P is unitary symmetry, C is ...
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### Complex conjugation in time-reversal $T$ symmetry v.s. in charge conjugation $C$ symmetry

How is the complex conjugation $K$ of time-reversal symmetry $T$ differed by the complex conjugation of charge conjugation $C$? How are they differed from each other? For instance, take the Dirac ...
1 vote
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### Zee's book on QFT on the spin-1/2 state has $T^2=-1$, why not $T^2=+1$

In Zee's book on QFT, p.103, he showed that the spin-1/2 state has $T^2=-1$ by finding that the $T = UK$ has a matrix $U\propto \sigma_2$ and a complex conjugation $K$. However, how do we know that we ...
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### How do the boundary conditions on lattice fields ensure that the particle has the correct symmetries in the perspective of CPT theorem?

Imagine for simplicity that we have scalar fields. Why don't we just impose on it the symmetries dictated by CPT theorem instead of using the boundary conditions as given in literature? A detailed ...
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### Why might violation of Lorentz symmetry imply violation of CPT symmetry?

Several articles that I am currently reading have suggested that violating Lorentz symmetry (equivalence of physical law in all inertial reference frames) implies the violation of CPT (charge-parity-...
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### How does Lorentz invariance link in with CPT symmetry?

I'm reading several articles on the relation between Lorentz symmetry (invariance under Lorentz transformations) and CPT symmetry; however, they all invoke high-level mathematics which I cannot ...
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1 vote
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### Polchinski's notes on CPT and Spin-Statistics

On Polchinski's website for Physics 221B, QFT, Winter 2015, there is a link that is supposed to contain notes on CPT and Spin-Statistics, but the link is dead. Does anybody have these notes, and if so ...
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