# Tagged Questions

Parity inversion P amounts to the sign flip of an odd number of coordinates (reflection). A parity-symmetric theory conserves P; since P²=I, the eigenvalues of P are 1 or -1. May be also used for formally analogous global, discrete, Z₂ symmetries, such as R- or G-parity.

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### 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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### Conjugation Operator General Question

I’m sitting here reading my particle physics book, and the Conjugation Operator is defined as: $C = -(-1)^{S+1}(-1)^{L}$, where $L =$ relative angular momentum for the $q\overline{q}$ pair for a ...
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### Different definitions of the parity transformation for the Dirac spinors

There are two definitions of the parity transformation acting on the Dirac spinors: $\Psi_P = \eta \gamma^0 \Psi$ with $\eta = i$ ($P^2=-1$ as in Srednicki) and $\eta=1$ ($P^2=+1$ as in Peskin & ...
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### How do we know that elementary particles possess definite parity?

As I was reading Griffiths' "Introduction to Elementary Particles" Wiley 2008, on chapter 4 "Symmetries", the question stroke me. The same as Parity operator (inversion in 3-dimensional space) we ...
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### What are the actual conventions for the standard model particles' intrinsic parities?

It is known that by fixing the intrinsic parity of three particles with linearly independent quantum numbers B, L and Q, the other particles' parities are fixed by the request that parity be conserved ...
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### Is $PT$ always a symmetry in (2+1)D?

Is the combination of parity $P: (x,y,t)\to (-x,y,t)$ (sometimes also called reflection $R$) and time reversal $T: (x,y,t)\to (x,y,-t)$ always a symmetry in (2+1)D theories with Lorentz or Galilean ...
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### Definition of partity in quantized Dirac Theory.

I'm studying from the book "An Introduction to Quantum Field Theory" from Michael E. Peskin and Daniel V. Schroeder, and I read the following: "The operator P should reverse momentum of a particle ...
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### Wu experiment beta decay

maybe it's a stupid question. But in Wu experiment she showed that parity in not conserved in beta decay. So how to say on general that this is true for any weak force interaction?
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### Physical meaning of parity in nuclear decays

I think it has to do with asymmetry in direction during emission of decay products .also what is implied physically when we say parity is violated in beta decays? I cannot imagine 'l' having an odd ...
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### Behavior of the Electric- and Magnetic-field under time reversal and parity

The behavior of the electric- $\mathbf{E}$ and the magnetic-field $\mathbf{B}$ und time reversal and parity can be calculated in different ways. My first solution is to study the transformation ...
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I have a problem I cannot solve on my own. I have given two states $\psi_1$ and $\psi_2$ and an Operator $O$ such that $P \psi_1 = \epsilon_1 \psi_2$, $P \psi_2 = \epsilon_2 \psi_2$ and $POP^{-1} = ... 1answer 64 views ### Parity operator with other operators I need to show the following: $$P x P^{-1} = -x, \ P p P^{-1} = -p, \ P L P^{-1} = L$$ where$P$is the parity operator and$x$,$p$and$L$are the position, momentum and angular momentum ... 1answer 68 views ### How can parity be meaningful in an affine space? I've recently begun a course in QFT (within a Physics Master's), and despite (admittedly limited) reading I can't get my head round the idea of parity. Here's what I think I understand: the Minkowski ... 1answer 72 views ### Demonstration that the$\langle f(x)\rangle$of an odd function$f(x)=-f(-x)$of position$x$in a symmetric potential well$V(x)=V(-x)$is null Consider a potential infinite well, which borders are$x=-a$and$x=a$. I pretend to demonstrate that the expected value of a odd function$f(x)$, i.e.,$\langle f(x)\rangle$, is null. We have the ... 1answer 81 views ### Regarding parity conservation in the decay$\omega \to \pi^0 \,\pi^+\, \pi^-$I'm somewhat confused by this decay. Associated vertex seem to be related to QCD residual terms contributing to the nuclear force, therefore they should manifest conservation of Isospin and Parity. ... 1answer 81 views ### “This operator is odd under parity” In problem 8.10 of Schaum's Quantum Mechanics they say: "We see that under the parity operator$r \rightarrow r$,$\theta \rightarrow \pi - \theta$and$\phi \rightarrow \pi + \phi$.. since ... 0answers 85 views ### Intrinsic parity When we apply parity on a field two times, we demand that we should get back the same field. This gives us,$P^{2} =1$, which implies,$ P \psi = e^{i \theta} \psi$. This extra phase factor is ... 1answer 72 views ### Is the decay of the positive Kaon into 3 pions a weak processs or strong one? The strangeness is not conserved in the decay of the positive Kaon into 3 pions. so this decay should be a weak process but on the other hand parity is conserved in this decay. Kaon has odd parity and ... 0answers 28 views ### Solutions to time-independent Schrödinger's equation with symmetrical (even) potential [duplicate] A problem from Griffith's Introduction to Quantum Mechanics asks to prove the following: Given a symmetric potential$V(x)(=V(-x))$, the solutions to the time-independent Schrödinger's equation ... 0answers 69 views ### Correct way to define parity of two parafermions I am checking the literature on parafermions and it seems that people define the parity of two parafermions to be$\gamma_{a}^{-1}\gamma_{b}$. Is this definition always valid? How does one come up ... 2answers 149 views ### Does charge conjugation affect parity? Notice that these transformations do not alter the chirality of particles. A left-handed neutrino would be taken by charge conjugation into a left-handed antineutrino, which does not interact in ... 0answers 99 views ### Parity of$n$-photon system The$C$-parity (charge conjugation) of an$n$-photon system is given by$(-1)^n$. If I'm not totally wrong, the intrinsic parity of a photon is$(-1)$. What is the parity$P$of a system of$n$... 1answer 420 views ### What's the idea behind Wu's experiment? Madame Wu discovered the parity violation in beta-decays. To do so, she took some Co-60 nuclei, which decay via beta-decay in Ni-60 with emission of electron, antineutrino and 2 gamma rays. She ... 2answers 247 views ### Spin, isospin, parity etc. in nuclear physics I have one question regarding these quantum numbers. When I read through my textbook, it sometimes just says something like: "And this atoms ground state has$J^{\pi} = 0^+$and isospin$+1$" - as an ... 0answers 37 views ### What are the parity of particles? [duplicate] When looking to see if particle collisions/decays are possible and what force they act through, how do you know the parity of particles to know whether they act through weak force? Is there a grouping ... 0answers 80 views ### Are mass terms forbidden in the Lagrangian because of parity violation or because fermions live in a complex representation? Normally one argues that we can't write down Lorentz AND gauge invariant mass terms, because of parity violation, i.e. l-chiral and r-chiral fields transform differently. This means that mass terms ... 0answers 79 views ### Is Witten's claim that gauge group representations get exchanged with its dual under parity correct? I'm currently reading Physics and Geometry by Witten, which I really liked up to the point where he claimed that we exchange representations$R$and$\tilde R$under parity transformations, where$R$... 0answers 71 views ### How can I prove that$\gamma^0$is the parity operator for Dirac fields? [closed] How can I prove that the parity operator on a Dirac field is$\gamma^0$? I was trying to prove it through Lorentz transformations but failed shortly. 1answer 99 views ### How is$J^{PC}$value experimentally determined for new types of particles? How is$J^{PC}$value experimentally determined for new types of particles? For example, this paper says ... Angular correlations in B+→X(3872)K+ decays, with X(3872)→ρ0J/ψ, ρ0→π+π− and J/ψ→μ+μ−, ... 1answer 113 views ### What's difference between C parity and charge? I know C parity as an operator : $$C\psi=\pm\psi$$ has two eigenvalues like parity operator P. But what I wonder is, i.e, is it true to say for a negative charged particle has (-) eigenvalue? If not ... 1answer 230 views ### Particle physics: Why is J^P called spin parity if J is the total angular momentum? Here is the question I am working on: "The Ξ- has spin parity=½+. It decays through the weak interaction into a Λ0 and a π- meson. If the spin parity of the Λ0 particle is 1/2+ and the spin parity of ... 0answers 101 views ### Fujikawa's method for 2+1-dimensional parity anomaly? Fujikawa's chiral rotation method is applied to calculate 3+1 dimensional chiral anomaly in many textbooks, but is there any counterpart of that method in deriving 2+1 dimensional parity anomaly, i.e. ... 1answer 368 views ### What is the definition of parity conservation? I searched quite hard, and am still confused what is the exact definition of parity conservation? For example, we have quantum system with initial state$\Phi_i$, and after decaying it comes to final ... 1answer 58 views ### Parity transformation is proper orthochronous? In 3+1 dimensional spacetime the parity transformation is $$P^\mu_{\;\,\nu}=\begin{pmatrix}+1&&&\\&-1&&\\&&-1&\\&&&-1\end{pmatrix}.$$ This is ... 0answers 90 views ###$\mathbb{Z}_2$topological insulators which obey inversion symmetry as well According to Fu & Kane (2006), systems with simultaneous time-reversal invariance and inversion symmetry have their$\mathbb{Z}_2$topological invariant given by the product of the parity ... 0answers 225 views ### Spin, parity, etc. conservation in decays/reactions I have a long list of short physics questions I'm reviewing, and there are several that ask about whether certain decays or reactions are allowed. Clearly these questions are testing my knowledge of ... 1answer 67 views ### Wigner's Theorem and discrete Symmetries According to my skript: A pure state is a ray:$\quad\{λψ\}$, where$ψ ∈ \mathcal H$,$||ψ|| =1$fixed and$λ ∈ \mathbb C$,$|λ| = 1$. Pure states are uniquely given by 1-dimensional orthogonal ... 0answers 99 views ### Determining Parity of Decaying Quantum System Show that a particle of spin$1$cannot decay into two identical particles of spin$0$. The$\rho$-meson has spin$1$and can decay into two spinless (spin-$0$)$\pi$-mesons, or pions, with ... 1answer 144 views ### Is the weak interaction Lagrangian invariant under parity transformations? The weak interaction term in the Lagrangian reads $$\bar \Psi \gamma_\mu P_L \Psi W^\mu.$$ Under parity transformations, because of$\Psi \rightarrow \gamma_0 \Psi$and$\gamma_5 \rightarrow ...
The weak force couples only to left-chiral fields, which is expressed mathematically by a chiral projection operator $P_L = \frac{1-\gamma_5}{2}$ in the corresponding coupling terms in the Lagrangian. ...