# Questions tagged [spinors]

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### Physical interpretation of spinor parameter $\epsilon$ in supersymmetry

Studying supersymmetry, I came across the introduction of the idea of SUSY field variations involving spinor parameters $\epsilon_{\alpha}$ under which actions must be invariant. This spinor parameter ...
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### Are super-symmetrical complements of physically realised theories (scalar, tensor, Yang-Mills etc.) compellingly first-order differential equations?

I made the observation that all super-symmetrical extensions of "standard" theories (SM and GR) are given by first order differential equations. In particular if in case of EFEs the super-...
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### Spinor covariant derivative conventions

The covariant derivative of a spinor $\psi$ is given by $$\nabla_\mu \psi = \partial_\mu \psi + \Omega_\mu \psi$$ where $\Omega_\mu$ is the spin connection. In equation (7.227) of Geometry, Topology ...
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### When a Hilbert space's state vector becomes a spinor?

Given a Hilbert space $\mathcal{H}$, we pick up some state vector $| \psi\rangle$ which lives in the Hilbert space $\mathcal{H}$. The $| \psi\rangle$ is a vector of the Hilbert space satisfies the ...
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### Rotation of a Spinor

I have a question about an intuitive approach on spinors as certain mathematical objects which have certain properties that make them similar to vectors but on the other hand there is a property which ...
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### How precisely can we set up a spin measurement of an atom about a particular axis?

The standard treatment is that once we measure a spin along the z-direction, it will be aligned with +1 or -1 spin along the z-direction. Then, when we measure it again along the z-direction, it has a ...
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### Scattering in QM/NRQM vs QFT

As discussed in this question: How does a wave packet get scattered? And shown in, for example, this video: https://www.youtube.com/watch?v=iq4lGVznr_8 In quantum mechanics particles are scattered due ...
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### What does the adjoint of a QFT Dirac plane-wave spinor represent, physically?

So, using the Dirac spinor notation for plane-wave electrons and positrons from HERE, and the definition of the adjoint of $\psi$ = $\psi^{*T} \gamma^0$, and applying that to the "up" ...
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### Finding spin up/spin down eigenstates along some arbitrary direction

So let's say I have some particle in some arbitrary state where its ket vector is given as a linear combination of the spin up eigenstate and the spin down eigenstate. The magnitude square of a, which ...
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### Normalization for Clebsch-Gordan Decomposition in Symmetrized Spinor Representation

In various references, including Rovelli's "Quantum Gravity," a method is presented for calculating the Clebsch-Gordan decomposition of two spin states. Suppose we have two spins with $j_{1}$...
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### Eigenspinor of helicity of electrons

I am reading the chapter in Griffth's introduction to elementary particle. By solving the momentum space Dirac equation and requiring the solution of the spinor to be the eigenspinor of the helicity ...
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