advanced_notions:quantum_field_theory:qcd_vacuum

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advanced_notions:quantum_field_theory:qcd_vacuum [2018/05/05 11:52] jakobadmin ↷ Links adapted because of a move operation |
advanced_notions:quantum_field_theory:qcd_vacuum [2018/05/05 12:39] (current) jakobadmin ↷ Links adapted because of a move operation |
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{{ :theories:quantum_theory:quantum_field_theory:pendulum-300x165.png?nolink&150|}} | {{ :theories:quantum_theory:quantum_field_theory:pendulum-300x165.png?nolink&150|}} | ||

- | A field in physics can be imagined as something like mattress. At every point in space we have an [[models:basic_models:harmonic_oscillator|harmonic oscillator]] and these oscillators are connected. (See the laymen explanation of [[theories:quantum_field_theory|Quantum Field Theory]]). In this picture, the vacuum state is when all these oscillators sit still. In a quantum field theory, this is never possible because there are always vacuum oscillation. Particles are then excitations of these ground state mattress. | + | A field in physics can be imagined as something like mattress. At every point in space we have an [[models:basic_models:harmonic_oscillator|harmonic oscillator]] and these oscillators are connected. (See the laymen explanation of [[theories:quantum_field_theory:canonical|Quantum Field Theory]]). In this picture, the vacuum state is when all these oscillators sit still. In a quantum field theory, this is never possible because there are always vacuum oscillation. Particles are then excitations of these ground state mattress. |

This picture is quite good but misses one crucial thing. There can be tunneling processes in the vacuum. The thing is that if we study the vacuum carefully, we notice that the vacuum state is not so simple as a set of harmonic oscillators that move a little. Instead much better approximation is a set of connected pendulums. At each point in space, we have a pendulum instead of an oscillator and these pendulums are connected. | This picture is quite good but misses one crucial thing. There can be tunneling processes in the vacuum. The thing is that if we study the vacuum carefully, we notice that the vacuum state is not so simple as a set of harmonic oscillators that move a little. Instead much better approximation is a set of connected pendulums. At each point in space, we have a pendulum instead of an oscillator and these pendulums are connected. | ||

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This is an important distinction, because in a quantum theory a pendulum can do something in addition to the usual small vacuum oscillation around its minimum. The pendulum can tunnel such that moves once around its revelation and ends up again in its ground position. While such a process would require usually a lot of energy, in a quantum theory it can happen even at minimum energy, i.e. when the quantum pendulum is in a ground state. This is known as a tunneling process. In this specific context, the tunneling is also called an instanton process. | This is an important distinction, because in a quantum theory a pendulum can do something in addition to the usual small vacuum oscillation around its minimum. The pendulum can tunnel such that moves once around its revelation and ends up again in its ground position. While such a process would require usually a lot of energy, in a quantum theory it can happen even at minimum energy, i.e. when the quantum pendulum is in a ground state. This is known as a tunneling process. In this specific context, the tunneling is also called an instanton process. | ||

- | These processes are important, because we need to take them into account when we do calculation in [[theories:quantum_field_theory|quantum field theory]]. All particles are exictations above the ground state and describe the ground state properly, we need to take these tunneling processes into account. | + | These processes are important, because we need to take them into account when we do calculation in [[theories:quantum_field_theory:canonical|quantum field theory]]. All particles are exictations above the ground state and describe the ground state properly, we need to take these tunneling processes into account. |

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advanced_notions/quantum_field_theory/qcd_vacuum.txt · Last modified: 2018/05/05 12:39 by jakobadmin

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