BeyondFar Posted June 12, 2021 Posted June 12, 2021 Quantum mechanics introduces the concept of identical particles, and according to the quantum number of spin, particles are divided into two categories: fermions with a half-integer spin and bosons with an integer spin. Are identical particles really exactly the same? In fact, the "identity" here is statistically identical, that is, "identical particles" refer to particles that satisfy the same statistical laws (Fermi statistics and Bose statistics). Specific to a single particle, it can still have different states, such as spin states. There is another difference between individual particles, which is the particle chirality, a brain-burning concept. According to the current theory, the chirality of a particle can be described by its spin or helicity. But the most puzzling thing is how to determine the chirality of a particle, that is, how to determine the direction of the particle's spin? For example, how to distinguish between left-handed electrons and right-handed electrons for electrons? Or, are there really right-handed electronics? Is the electrical polarity of electrons related to spin chirality?
quantumspin Posted June 14, 2021 Posted June 14, 2021 spin, chirality and helicity are all different. firstly spin is not 'spin', its just called that as a hangover from the early days of qm when the the magnetism associated with particles was thought to be due to particles 'spinning' on their own axes (since moving electric fields produce magnetic fields). Besides, a mathematical point particle cannot 'spin', since rotation isnt defined for a mathematical point. The helicity of a particle may change depending on your velocity relative to it, but its chirality is independent of your relative velocity. the difference between chirality and helicity is this: imagine you had a right handed glove and you throw it such that the palm of the glove is always facing the direction of the gloves forward trajectory. The glove can also be rotating about the forward-trajectory-axis, if it rotates clockwise as it moves forward, the glove has right helicity, if anti-clockwise, it has left helicity. But either way it is still a chirally right-handed glove. If you move parallel to the right helical rotating glove, but faster than it, relative to you the glove will be moving in the backwards direction, and therefore, relative to this backward direction as an axis, it will be seen to be rotating anticlockwise, in other words left helical. The notions of 'chirality' and 'helicity' are fundamentally geometric concepts and not specifically only 'properties' of particles. The polarity of the electron is not related to chirality, the mass basis electron is a mixture of both left and right electrons. see the video: link to commercial site removed by moderator per rule 2.7 and like and comment. I will answer if I can.
swansont Posted June 14, 2021 Posted June 14, 2021 On 6/12/2021 at 6:43 PM, BeyondFar said: Quantum mechanics introduces the concept of identical particles, and according to the quantum number of spin, particles are divided into two categories: fermions with a half-integer spin and bosons with an integer spin. Are identical particles really exactly the same? In fact, the "identity" here is statistically identical, that is, "identical particles" refer to particles that satisfy the same statistical laws (Fermi statistics and Bose statistics). Specific to a single particle, it can still have different states, such as spin states. There is another difference between individual particles, which is the particle chirality, a brain-burning concept. They only obey these statistics if they are identical, so yes, they are exactly the same
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