Questions tagged [cpt-symmetry]

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Which constrained trajectories of an ensemble of charges maintain time reversibility without additional fields?

Maxwell's equations are time reversible, and the fields can be written in terms of the sources via the Lienard-wiechert fields. However, the fields written in terms of the sources alone are not ...
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How do the time reversed retarded solutions to Maxwell's equations maintain T-symmetry?

Maxwell's equations are T-symmetrical in that they remain invariant to a change in the sign of $dt$ if the sign of $B$ and $J$ are also reversed. Hence the corresponding time reversed solution is ...
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84 views

C, P and T transformations of $\phi$ that preserves symmetry

I have a series of exercises regarding C, P and T symmetry but I am not really sure how to start with the problems. If anyone could help me with one of the problems, or show me a few example problems ...
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What is CPT, really?

The naive statement for the "CPT theorem" one usually finds in the literature is "relativistic theories should be CPT invariant". It is clear that this statement is not true as written, e.g. ...
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Decomposing the $\mathcal{N} = 4$ massless graviton supermultiplet

I'm trying to solve the following exercise: Construct the physical states of the $\mathcal{N} = 4$ massless graviton supermultiplet, starting from a Clifford vacuum of helicity $λ_0 = 0$. Decompose ...
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47 views

Electric dipole moment (EDM) and CP violation

It's well known that a non-zero value for the electric dipole moment (EDM) would imply CP violation. If we consider the interaction Hamiltonian of an EDM $d$ with an electric field $\vec{E}$, $$ H = -...
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QED $PC$ conservation

I'm trying to prove that the QED Lagrangian $$\mathscr{L}=\bar{\psi}(i\!\!\not{\!\partial}-m)\psi - \frac{1}{4}F^{\mu\nu}F_{\mu\nu} - J^\mu A_\mu$$ Is invariant under P and C. The two fields transform ...
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Where can I get an introduction to the CPT symmetry?

Are there any good books that provide a good background to the CPT symmetry? I'd appreciate some references. Books or Public access papers will also suffice.
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Why isn't EM radiation from an accelerated charge time reversible?

Let a charge $q$ enter a constant magnetic field $B$ at 90 degrees, hence radiating EM energy-momentum and spiraling inwards to some point as it slows down. Time reversing this, including the current ...
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145 views

Why aren't black holes antimatter fountains?

As I understand it, nothing can escape a black hole because the only worldlines leading 'out' from the event horizon point backwards in time. As I understand it, antimatter is time-reversed ordinary ...
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Is time reversal of emission and absorption of radiation by a point charge a postulate or consequence of CED?

Suppose a point charge is accelerated by an external field, hence radiating irreversible energy-momentum given by the Lienard-Wiechert fields. We can time reverse this so that the radiation instead ...
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Does it mean time reverses if all particles were antiparticles and vice versa?

First of all, I'm not major in physics and the question might seems stupid, as I'm layman studying for my self-interest and I really don't know much about it. I only think it might open some ...
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83 views

Does charge conjugation symmetry sit in the Lorentz group?

We know the Lorentz group is $O(3,1)$ in 4 dimensional spacetime. We know that there are 4 disconnected components in Lorentz group $O(3,1)$, and https://math.stackexchange.com/q/2204349/ $$\pi_0(\...
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Are all processes time/CPT-reversible, e.g. measurement, stimulated emission, state preparation, Big Bang?

"The CPT theorem says that CPT symmetry holds for all physical phenomena, or more precisely, that any Lorentz invariant local quantum field theory with a Hermitian Hamiltonian must have CPT symmetry." ...
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Does the CPT theorem hold for all spacetime dimensions?

I can't find any reference which mentions the dependence of the theorem on spacetime dimension, but it would be very interesting to know what if any it has!
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CPT transformation for bilinears

In the page 5 of the document 'CPT Symmetry and Its Violation' by Ralf Lehnert (https://core.ac.uk/download/pdf/80103866.pdf), appears a discussion about how the spin-statistics theorem applies to the ...
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Arrow of time and CPT symmetry

It's been a few years since my physics degree. But I've been wondering: if you look at pictures of collisions at CERN, isn't it obvious which way time flows - simply on a probability basis? The ...
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Mathematical representation of Symmetry Transformation

Consider a general Hamiltonian that is made up of three terms $\mathcal{H}$ = term I + term II + term III . Suppose the combination of charge conjugation and parity (CP) is a symmetry of this ...
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252 views

Why is the Higgs $CP$ even?

Why was it always assumed that the Higgs boson is a CP even particle? I understand that experimentally, it just is so but I am under the impression that before its discovery people took it to be CP ...
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Antiparticles, CPT and leptogenesis

When people are being careful they'll tell you that antiparticles are the CPT conjugates of particles. You can't say that they are C conjugates or CP because these, while they do reverse the charge, ...
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316 views

C and T Symmetry of Free Dirac Lagrangian

I want to show the $C$ and $T$ symmetry of the free Dirac Lagrangian $$\mathcal{L}=\overline{\psi}\left(i\gamma^\mu\partial_\mu-m\right)\psi.$$ Following the notation of Peskin, Schroeder, we have ...
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2answers
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Why is it important that the combination of charge, parity & time reversal symmetry not violated?

If looking for more particles or decays that violate CP symmetry can explain why there is so few antimatter in the known universe, I guess finding things that violate CPT symmetry might helps clear up ...
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128 views

Is time reversal symmetry true on the microscopic level?

I often hear that on the microscopic level, time-reversal symmetry is true for all physical processes. However, I can easily come up with counterexamples that seem to disprove this: Two particles of ...
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Does the weak force obey the CPT symmetry? How?

I have read that the weak force does not obey the charge symmetry, the parity symmetry, and the time reversal symmetry. Then how does it obey the CPT symmetry?
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What are the assumptions that $C$, $P$, and $T$ must satisfy?

I am not asking for a proof of the $CPT$ theorem. I am asking how the $CPT$ theorem can even be defined. As matrices in $O(1,3)$, $T$ and $P$ are just $$ T = \begin{pmatrix} -1 & 0 & 0 & ...
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How is a half-odd integer spin field defined in the Wightman axioms?

Can anyone give me a proper definition of 'half-odd integer spin fields' in terms of the Wightman axioms? I'm trying to prove the anti-unitarity of the PCT operator in 'PCT, Spin and Statistics, and ...
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What operator gives the mass of a particle?

Talking about why a particle and its antiparticle have the same mass, my professor said the Hamiltonian commutes with TCP, so mass is conserved. I don't understand that.
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Clarifying PT symmetry

I understand that if a Hamiltonian remains invariant under the following transformations then it is PT invariant, \begin{eqnarray} \mathrm{Parity \; reversal:} \; \; \hat{p} \to -\hat{p} \; \; \...
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Does reversing time give parity reversed antimatter or just antimatter?

Feynman's idea states that matter going backwards in time seems like antimatter. But, since nature is $CPT$ symmetric, reversing time ($T$) is equivalent to $CP$ operation. So, reversing time gives ...
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What is the definition of the charge conjugation?

I seem to have troubles finding definitions of the charge conjugation operator that are independant of the theory considered. Weinberg defined it as the operator mapping particle types to ...
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200 views

Clarification on CPT symmetry

CPT symmetry, as I understand it, holds that if all charge, parity, and time were reversed (a mirror-image antimatter time-reversed universe), that universe would behave identically to our current ...
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CPT symmetry as it applies to matter/antimatter

I've heard/read a couple different definitions for antimatter: it is charge-reversed matter (typical definition, for the lay person at least), or it's time-reversed matter (as described in QED). ...
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chiral symmetry condensate and 2SC, CFL breaking C, P and T symmetry?

Because we know that chiral symmetry condensate causes the chiral symmetry breaking, and it produces Goldstone modes of pseudo-scalars, so I believe that chiral symmetry breaking also breaks the T ...
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Is N=6 SUSY gravitino multiplet self-CPT?

I would like to understand why the $N=6$ gravitino (massless) multiplet $$\left(-\frac32,(-1)^{6},(-\frac12)^{15}, 0^{20}, (+\frac12)^{15}, +1^6, +\frac32 \right)$$ is not CPT self-conjuguate?. It ...
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83 views

How to understand $T^2=(-1)^{N_f}$ in terms of operator matrices on Hilbert space

For a time reversal symmetry operator $\hat{T}$, we have $$\hat{T}^2=(-1)^{N_f}$$ for a fermionic (electronic) system. How do we understand $\hat{T}^2=(-1)^{N_f}$ in terms of operator matrices on the ...
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Is it possible to have renormalisable C-, P-, or T-violating terms in QED?

In a recent paper (1710.01791), Witten claims that there are no renormalisable $\mathrm C,\mathrm P,\mathrm T$-violating terms that can be included in the QED Lagrangian: What does this picture say ...
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Instanton effects on condensates: (pseudo)scalars, (pseudo)vectors, tensor

I have heard that the instanton effect in quark matter causes the di-quark condensate to be Lorentz scalar. As opposed to the Lorentz scalar, there are possibilities that the condensates are Lorentz ...
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221 views

CPT-symmetric initial state

Consider a hypothetical state of the universe such that it coincides with its CPT “mirror-image”. I.e., let us reflect positions of all objects by some plane (parity inversion), reverse all momenta (...
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176 views

How to classify the symmetry $C$, $P$ and $T$?

What is the difference between internal symmetries and space-time symmetries? Where would the $C$, $P$ and $T$ symmetries be classified?
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Discovery of anti-deuteron and the implication of CPT violation

From this review by Antonino Zichichi 2009 and this review from T. D. Lee in 2007, it is said that Dirac is very upset when hearing the discovery of anti-deuteron (anti-matter of deuteron, the nucleus ...
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What feature of QFT requires the C in the CPT theorem?

Classical tensor field theories have a PT theorem, so what changes in a QFT to require charge conjugation to be a part of the theorem? Charge conjugation seems a bit unrelated to space-time, but is an ...
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Why did they need such short lived isotopes to find pear shaped nuclei?

Recently, pear-shaped nuclei have been discovered. This discovery has interesting implications, as noted in this question: Do pear-shaped nuclei really have anything to do with time travel? At the ...
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712 views

C-parity violation evidence

I know about the CP-violation experiments from the 60's and the P-violation from the 50's. But, is there a similar experiment which displays (perhaps historically in the same way as the experiements ...
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Parity conservation in second harmonic generation?

The second harmonic arises from susceptibility of third rank tensor $X^{(2)}$ which have (-1) parity. page 28 Let say two photons are absorbed and one is emitted, so the total change in parity is $(...
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435 views

Conservation of $C$-Parity and $P$-parity

Under what situations are $C$-Parity $C=(-1)^{L+S}$ and/or $P$-parity $P=-(-1)^L$ conserved? ( $L$ here is the relative angular momentum and S is the total intrinsic spin). It would make sense that ...
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588 views

Wave function of particle and antiparticle

The wave functions of particle and antiparticle are related by complex conjugation and wavefunction $Ψ$ must be complex for particle such as $n$, $p$. Is there way to prove this mathematically? Can we ...
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Could an antimatter-dominated end of universe fix CPT?

My question is about the apparent CPT violation of the observed universe, due to the imbalance of matter and antimatter, but first I have a motivating observation: General relativity respects time ...
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Symmetry properties of the scalar potential and the vector potential

How do the scalar potential $\phi(x,t)$ and vector potential $A(x,t)$ behave under the parity and time-reversal transformations?
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Application of CPT invariance : some trivial algebra

I am having some problem in understanding one step in the following algebra. Consider an interaction where initial state is defined as $ \left|i\right> $ and final state by $ \left|f\right> $....
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Is the right-handed antineutrino the CPT conjugate of the left-handed neutrino?

I am working from the book Massive Neutrinos in Physics and Astrophysics by Mohapatra and Pal (which is available here). On page 66, the authors claim that $\psi_{L}$ is the $\mathcal{CPT}$ conjugate ...