Vacuum microarc

The physics of stationary vacuum microarc in a wide interelectrode gap with the perveance corresponding to a geometry of the Müller electron projector type and the Langmuir-Blodgett function α²≥5 is considered on a qualitative level. Under these conditions, the electric field at the cathode can exhibit a significant (severalfold) increase due to a positive space charge of microarc, which makes field electron emission possible. The most important features of the continuity equation, Poisson equation, and thermal conductivity equation describing this system are considered.     

Vacuum Instability

NAbstract Following fresh attempts to resolve the problem of the energy density of the vacuum, we reconsider the case where the cosmological constant is derived from a higher-dimensional version of general relativity, and interpret the gauge-dependence of Λ as a dynamical effect. This leads to a relation between the change in Λ and the line element (action) which is independent of gauge choices and fundamental constants: dΛds² = −6. This implies that the (classical) vacuum is unstable, with implications for particle production.     

The Light-Front Vacuum

We discuss the relation between the trivial light-front vacuum and the non-trivial Heisenberg vacuum.     

Vacuum Cerenkov radiation

Within the classical Maxwell-Chern-Simons limit of the standard-model extension, the emission of light by uniformly moving charges is studied confirming the possibility of a Cerenkov-type effect. In this context, the exact radiation rate for charged magnetic point dipoles is determined and found in agreement with a phase-space estimate under certain assumptions.     

Vacuum Susceptibility Calculation

The vector susceptibility is investigated numerically in the Dyson-Schwinger approach. The results agree with those obtained analytically previously by using a simple gluon propagator.     

Vacuum Boundary Effects

The Casimir effect is highly dependent on the shape and structure of space boundaries. This dependence is encoded in the variation of vacuum energy with the different types of boundary conditions. We analyze from a global perspective the properties of the Casimir energy as a function on the largest space of the consistent boundary conditions M_F\mathcal{M}_{F} for a massless scalar field confined between to homogeneous parallel plates. In particular, we analyze the analytic properties of this function and point out the existence of a third order phase transition at periodic boundary conditions. We also characterize the boundary conditions which give rise to attractive or repulsive Casimir forces. In the interface between both regimes we find a very interesting family of boundary conditions without Casimir effect, and fully characterize the boundary conditions which do not induce any type of Casimir force.     

Vacuum Susceptibility Calculation

The vector susceptibility is investigated numerically in the Dyson-Schwinger approach. The results agree with those obtained analytically previously by using a simple gluon propagator.     

Vacuum phonon tunneling

Field-induced phonon tunneling, a previously unknown mechanism of interfacial thermal transport, has been revealed by ultrahigh vacuum inelastic scanning tunneling microscopy (STM). Using thermally broadened Fermi-Dirac distribution in the STM tip as in situ atomic-scale thermometer we found that thermal vibrations of the last tip atom are effectively transmitted to sample surface despite few angstroms wide vacuum gap. We show that phonon tunneling is driven by interfacial electric field and thermally vibrating image charges, and its rate is enhanced by surface electron-phonon interaction.     

A Characterization of Vacuum

In this note, we use a Killing vector field on a 4-dimensional Lorentzian space-time (M,g), to obtain sufficient conditions for (M,g) to be a vacuum.     

Vacuum Arc Anode Phenomena

This paper briefly reviews anode phenomena in vacuum arcs, specially experimental work. It discusses, in succession, arc modes at the anode, anode temperature measurements, anode ions, transitions of the arc into various modes (principally the anode spot mode), and theoretical explanations of anode phenomena. The two most common anode modes in a vacuum arc are a low current mode where the anode is basically passive, acting only as a collector of particles emitted from the cathode, and a high current mode with a fully developed anode spot. Characteristically this anode spot has a temperature near the atmospheric boiling point of the anode material and is a copious source of vapor and energetic ions. However, other anode modes can exist. A low current vacuum arc with electrodes of readily sputterable material may emit a flux of sputtered atoms from the anode. Usually this sputtered flux will have little effect upon the vacuum arc, but in certain circumstances it could be significant. A vacuum arc doesn't always transfer directly from a low current mode to the anode spot mode. In appropriate experimental conditions, formation of an anode spot may be preceded by the formation of an anode footpoint. This footpoint is luminous, but much cooler than a true anode spot. Finally, (again in appropriate circumstances) several small anode spots may form instead of one large anode spot. With sufficient increase in arc current or arcing time these will usually combine to form a single large active spot.     

Vacuum metrics without symmetry

Vacuum metrics admitting null, geodetic, expanding, shear-free congruences are investigated. A new solution is derived which contains three holomorphic functions of a complex variable. It includes, as special cases, a number of well-known solutions such as those of Kerr and Taub-NUT. In general, however, it admits no Killing vectors.This work was supported in part by Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under AFOSR Grant No. 903-67 and National Aeronautics and Space Administration under NASA Grant No. NGL 44-004-001.     

Entanglement from the Vacuum

We explore the entanglement of the vacuum of a relativistic field by letting a pair of causally disconnected probes interact with the field. We find that, even when the probes are initially non-entangled, they can wind up to a final entangled state. This shows that entanglement persists between disconnected regions in the vacuum. However the probe entanglement, unlike correlations, vanishes once the regions become sufficiently separated. The relation between entropy, correlations and entanglement is discussed.     

Vacuum stability and supersymmetry

Radiative effects are shown to cause breakdown of the semiclassical ground state in a massless theory of fermions and spinless bosons when the coupling of fermions to bosons is larger than the boson self-coupling. Supersymmetry forms the boundary, in coupling constant space, separating theories with and without stable semiclassical vacua.     

Vacuum ultraviolet radiation source

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 509–512, March, 1991.     

Vacuum condensates of QCD

We study the properties of QCD vacuum state in this paper. The values of various local quark vacuum condensates, quark-gluon mixed vacuum condensates, and the structure of non-local quark vacuum condensate are predicted by the solution of Dyson-Schwinger Equations in "rainbow" approximation with three sets of different parameters for effective gluon propagator. The light quark virtuality is also obtained in a consistent way. Our all theoretical results here are in good agreement with the empirical values used widely in literature and many other theoretical calculations.     

Vacuum nonsingular black hole

The spherically symmetric vacuum stress-energy tensor with one assumption concerning its specific form generates the exact analytic solution of the Einstein equations which for larger coincides with the Schwarzschild solution, for smallr behaves like the de Sitter solution and describes a spherically symmetric black hole singularity free everywhere.This essay received the fifth award from the Gravity Research Foundation, 1991     

Entropy and Vacuum Radiation

It is shown that entropy increase in thermodynamic systems can plausibly be accounted for by the random action of vacuum radiation. A recent calculation by Rueda using stochastic electrodynamics (SED) shows that vacuum radiation causes a particle to undergo a rapid Brownian motion about its average dynamical trajectory. It is shown that the magnitude of spatial drift calculated by Rueda can also be predicted by assuming that the average magnitudes of random shifts in position and momentum of a particle correspond to the lower limits of the uncertainty relation. The latter analysis yields a plausible expression for the shift in momentum caused by vacuum radiation. It is shown that when the latter shift in momentum is magnified in particle interactions, the fractional change in each momentum component is on the order of unity within a few collision times, for gases and (plausibly) for denser systems over a very broad range of physical conditions. So any system of particles in this broad range of conditions would move to maximum entropy, subject to its thermodynamic constraints, within a few collision times. It is shown that the spatial drift caused by vacuum radiation, as predicted by the above SED calculation, can be macroscopic in some circumstances, and an experimental test of this effect is proposed. Consistency of the above results with quantum mechanics is discussed, and it is shown that the diffusion constant associated with the above Brownian drift is the same as that used in stochastic interpretations of the Schrödinger equation.     

A Rotating Quantum Vacuum

We investigate how a uniformly rotating frame is defined as the rest frame of an observer rotating with constant angular velocity around the z axis of an inertial frame. Assuming this frame to be a Lorentz one, we second quantize a free massless scalar field in the rotating frame and obtain that creation-annihilation operators of the field are not the same as those of an inertial frame. This leads to a new vacuum state—a rotating vacuum. After this, introducing an apparatus device coupled linearly with the field, we obtain that there is a strong correlation between the number of Trocheries-Takeno particles (in a given state) obtained via canonical quantization and the response function of the rotating detector. Finally, we analyze polarization effects in circular accelerators in the proper frame of the electron, making a connection with the inertial frame point of view.