According to present-day understanding of what is called the vacuum state or the quantum vacuum, it is "by no means a simple empty space", and again: "it is a mistake to think of any physical vacuum as some absolutely empty void." According to quantum mechanics, the vacuum state is not truly empty but instead contains fleeting electromagnetic waves and particles that pop into and out of existence.
The QCD vacuum of quantum chromodynamics is the object of study in the relativistic heavy ion collider and the large hadron collider, and is related to the so-called vacuum structure of strong interactions.
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.
For a relativistic field theory, the vacuum is Poincaré invariant. Poincaré invariance implies that only scalar combinations of field operators have non-vanishing VEV's. The VEV may break some of the internal symmetries of the Lagrangian of the field theory. In this case the vacuum has less symmetry than the theory allows, and one says that spontaneous symmetry breaking has occurred. See Higgs mechanism, standard model and Woit.
In principle, it is possible for the experimental electrical permittivity ε of the vacuum state to deviate from the defined scalar value ε0 of the electric constant due to quantum corrections to Maxwell's equations. These theoretical developments are described, for example, in Dittrich and Gies. In particular, the theory of quantum electrodynamics predicts that vacuum should exhibit nonlinear effects that will make it behave like a birefringent material with ε slightly greater than ε0 for extremely strong electric fields. Explanations for dichroism from particle physics, outside quantum electrodynamics, also have been proposed. Active attempts to measure such effects have been unsuccessful so far.
WIPO ASSIGNS PATENT TO PACKAGING TECHNOLOGIES & INSPECTION, FOR "AT REST VACUUM STATE FOR VACUUM DECAY LEAK TESTING METHOD AND SYSTEM" (AMERICAN INVENTORS)
Jun 01, 2011; GENEVA, June 1 -- Publication No. WO/2011/063227 was published on May 26. Title of the invention: "AT REST VACUUM STATE FOR...
US Patent Issued on Oct. 1 for "At Rest Vacuum State for Vacuum Decay Leak Testing Method and System" (New Jersey Inventors)
Oct 01, 2013; ALEXANDRIA, Va., Oct. 1 -- United States Patent no. 8,544,315, issued on Oct. 1."At rest vacuum state for vacuum decay leak...
US Patent Issued to Samsung Mobile Display on Sept. 6 for "Electroluminescent Display Device Provided with a Photonic Crystal Layer Incorporating Voids in a Vacuum State" (South Korean Inventors)
Sep 09, 2011; ALEXANDRIA, Va., Sept. 9 -- United States Patent no. 8,013,514, issued on Sept. 6, was assigned to Samsung Mobile Display Co....