International 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...

Determination of the interaction impedance of helix slow-wave structures - Vacuum Electronics Conference, 2000. Abstracts. International

The computer simulation of helix travelling-wave tubes requires accurate information about the phase velocity, interaction impedance and attenuation of the helix slow wave structure at each frequency. This has received considerable attention, from the pioneering work of Pierce onwards, and it is possible to compute or measure the phase velocity with sufficient accuracy. The methods available fo...

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...