Non-vanishing Vacuum State
If the quantum field theory can be accurately described through perturbation theory, then the properties of the vacuum are analogous to the properties of the ground state of a quantum mechanical harmonic oscillator (or more accurately, the ground state of a QM problem). In this case the vacuum expectation value (VEV) of any field operator vanishes. For quantum field theories in which perturbation theory breaks down at low energies (for example, Quantum chromodynamics or the BCS theory of superconductivity) field operators may have non-vanishing vacuum expectation values called condensates. In the Standard Model, the non-zero vacuum expectation value of the Higgs field, arising from spontaneous symmetry breaking, is the mechanism by which the other fields in the theory acquire mass.
Read more about this topic: Vacuum State
Famous quotes containing the words vacuum and/or state:
“When a daughter tries suicide
and the chimney falls down like a drunk
and the dog chews her tail off
and the kitchen blows up its shiny kettle
and the vacuum cleaner swallows its bag
and the toilet washes itself in tears ...”
—Anne Sexton (1928–1974)
“The health of the soul is something we can be no more sure of than that of the body; and though a man may seem far from the passions, yet he is in as much danger of falling into them as one in a perfect state of health of having a fit of sickness.”
—François, Duc De La Rochefoucauld (1613–1680)