Student colloquium - Mads Andresen: Physics of the Quantum Vacuum: The effects of quantum fluctuations
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Supervisor: Nikolaj Thomas Zinner
Unlike its classical counterpart, the quantum vacuum is far from empty. For quantum fields, fluctuations are always present, even in their lowest energy state. This results in a very dynamic quantum vacuum filled with energy and virtual particles jumping in and out of existence as direct consequences of these fluctuations. The effects of quantum fluctuations include: 1) Spontaneous emission, which can be explained as the interaction of an excited atom with the vacuum state E-field. 2) The Casimir effect, in which two perfectly conducting plates in vacuum experience a force due to a change in the vacuum energy between them compared to the vacuum outside. A change which is caused by the new boundary conditions on the electromagnetic fields between the plates.
There are still open questions about the physical significance of vacuum energy. The infinite vacuum energy in quantum electrodynamics seems entirely inconsistent with a finite cosmological constant, and attempts to correct this have, so far, led to a cosmological constant many magnitudes larger than the known value.