advanced_notions:quantum_field_theory:qcd_vacuum
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advanced_notions:quantum_field_theory:qcd_vacuum [2018/05/03 10:47] jakobadmin |
advanced_notions:quantum_field_theory:qcd_vacuum [2018/05/05 11:52] jakobadmin ↷ Links adapted because of a move operation |
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| <tabbox Intuitive> | <tabbox Intuitive> | ||
| {{ :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: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|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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| - | There is a non-zero energy density of the [[models:qcd|QCD]] vacuum due to [[advanced_tools:non-perturbative_qft|non-perturbative effects]] (source: Eq. 1.26 [[http://inspirehep.net/record/197666||here]]) | + | There is a non-zero energy density of the [[models:standard_model:qcd|QCD]] vacuum due to [[advanced_tools:non-perturbative_qft|non-perturbative effects]] (source: Eq. 1.26 [[http://inspirehep.net/record/197666||here]]) |
| $$ \epsilon_{vac} \simeq -\frac{b}{128\pi^2}\langle 0|(gG_{\mu\nu}^a)^2|0\rangle \simeq 0.5 \mathrm{\ GeV/fm^3}$$ | $$ \epsilon_{vac} \simeq -\frac{b}{128\pi^2}\langle 0|(gG_{\mu\nu}^a)^2|0\rangle \simeq 0.5 \mathrm{\ GeV/fm^3}$$ | ||
advanced_notions/quantum_field_theory/qcd_vacuum.txt · Last modified: 2018/05/05 12:39 by jakobadmin
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