ECONOMISCH VACUUM

Vacuum defects without a vacuum

Topological defects can arise in symmetry breaking models where the scalar field potential V (φ) has no minima and is a monotonically decreasing function of |φ|. The properties of such vacuumless defects are quite different from those of the “usual” strings and monopoles. In some models such defects can serve as seeds for structure formation, or produce an appreciable density of miniblack holes...

Vacuum Energy and Θ–vacuum

The highly non-trivial structure of the θ–vacuum encodes many of the fundamental properties of gauge theories. In particular, the response of the vacuum to the θ–term perturbation is sensitive to the existence of confinement, chiral symmetry breaking, etc. We analyze the dependence of the vacuum energy density on θ around two special values, θ = 0 and θ = π. The existence or not of singular beh...

Vacuum Gauge to Vacuum Pump Valve

Vacuum Birefringence as a Vacuum Emission Process

We argue that the phenomenon of vacuum birefringence in strong inhomogeneous electromagnetic fields can be most efficiently analyzed in terms of a vacuum emission process. In this contribution, we exemplarily stick to the case of vacuum birefringence in a stationary perpendicularly directed, purely magnetic background field extending over a finite spatial extent. Similar field configurations ar...

On vacuum-vacuum amplitude and Bogoliubov coefficients

Even if the electromagnetic field does not create pairs, virtual pairs lead to the appearance of a phase in vacuum-vacuum amplitude. This makes it necessary to distinguish the inand out-solutions even when it is commonly assumed that there is only one complete set of solutions as, for example, in the case of a constant magnetic field. Then inand out-solutions differ only by a phase factor which...