Peccei–Quinn theory | Wikipedia audio article скачать в хорошем качестве

Peccei–Quinn theory | Wikipedia audio article

This is an audio version of the Wikipedia Article: https://en.wikipedia.org/wiki/Peccei%... Listening is a more natural way of learning, when compared to reading. Written language only began at around 3200 BC, but spoken language has existed long ago. Learning by listening is a great way to: increases imagination and understanding improves your listening skills improves your own spoken accent learn while on the move reduce eye strain Now learn the vast amount of general knowledge available on Wikipedia through audio (audio article). You could even learn subconsciously by playing the audio while you are sleeping! If you are planning to listen a lot, you could try using a bone conduction headphone, or a standard speaker instead of an earphone. Listen on Google Assistant through Extra Audio: https://assistant.google.com/services... Other Wikipedia audio articles at: https://www.youtube.com/results?searc... Upload your own Wikipedia articles through: https://github.com/nodef/wikipedia-tts Speaking Rate: 0.7809576868126455 Voice name: en-AU-Wavenet-D "I cannot teach anybody anything, I can only make them think." Socrates SUMMARY ======= In particle physics, the Peccei–Quinn theory is a well-known proposal for the resolution of the strong CP problem. It was formulated by Roberto Peccei and Helen Quinn. The theory proposes that the QCD Lagrangian be extended with a CP-violating term known as the θ term. Because experiments have never measured a value for θ, its value must be small if it exists. Peccei–Quinn theory predicts that the small θ parameter is explained by a dynamic field, rather than a constant value. Because particles arise within quantum fields, Peccei–Quinn theory predicts the existence of a new particle, the axion. The potential which this field carries causes it to have a value which naturally cancels, making the θ parameter uneventfully zero. Peccei–Quinn symmetry presents θ as a functional component—a global U(1) symmetry under which a complex scalar field is charged. This symmetry is spontaneously broken by the vacuum expectation value obtained by this scalar field, and the axion is the massless Goldstone boson of this broken symmetry. This Peccei–Quinn symmetry is inexact because it is anomalously broken by QCD instantons. If there is a compensatory term canceling the QCD anomaly breaking term, the axion becomes an exactly massless Goldstone boson and θ is no longer fixed. The effective potential of the axion is the summed potential above the QCD scale; with the potential term induced by nonperturbative QCD effects. If the axion is fundamental, or emerges at a scale far higher than the QCD scale, then the dimension 5 axion coupling term a T r [ F ∧ F ] {\displaystyle a\mathrm {Tr} [F\wedge F]} is suppressed by 1 / Λ {\displaystyle 1/\Lambda } where Λ {\displaystyle \Lambda } is the scale of the axion. Because of this, in order for θ to be so small at the minimum of the effective potential, the bare potential has to be many orders of magnitude smaller than the instanton induced potential, compounded by the Λ {\displaystyle \Lambda } factor. This requires quite a bit of reconciliation with an approximate global symmetry, for which there is no current explanation.