Vacuum Value Research Articles

Exact Solutions of Quantum Massive Spin-1 Field Equations and Their Application to the Hawking-Unruh Effect

A generalisation of the Stueckelberg aCtion is implemented to describe spin-1 fields propagating in a four-dimensional Rindler manifold. Exact solutions of the field equations are obtained and the expectation value in the Minkowski vacuum state of the Rindler particle number operator is evaluated in the massive and massless cases. Further on, the energy-momentum tensor expectation value in the Rindler vacuum is computed and its qualitative behavior is analysed. In the zero mass limit we rederive the results obtained by other methods. Like this case, in the massive one it is shown that the energy-momentum spectrum is not Planckian. For small values of the mass, this spectrum is characterised by the Bose distribution function apart from a modification generated by a reduced density of states factor which is explicitly calculated.

The cosmological constant and volume-preserving diffeomorphism invariants

Observables in the quantum field theories of ( D − 1)-form fields, A , on D-dimensional, compact and orientable manifolds, M, are computed. Computations of the vacuum value of the energy-momentum tensor, 〈 T ab 〉, on manifolds without boundaries, find it to be the metric times a function of the volume of spacetime, Ω(M). Whereas, on manifolds with boundaries, 〈 T ab 〉 is of the form due to a cosmological constant. The correlation functions of another set of operators give intersection numbers on M. Furthermore, a similar computation for products of Wilson area operators results in a function of the volumes of the intersections of the submanifolds the operators are defined on. In addition, scalar field couplings are introduced and potentials are induced after integrating out the A -field. Lastly, the thermodynamics of the pure theories is found to be analogous to the zero-point motion of a scalar particle.

Electric field effects on the quantum efficiency of CsI photocathodes in gas media

We have measured the quantum efficiency (QE) of CsI photocathodes as a function of the electric field strength in a parallel-plate geometry, in CH 4, C 2H 6 and i-C 4H 10 both in charge collection and multiplication modes. It was found that in the collection plateau the QE value in gases is lower compared to that of vacuum and is independent of the field; in gas media the QE starts to increase at the transition between collection and multiplication modes and reaches the vacuum value at high gas gain. We explain this effect by a decrease of the electron-molecule elastic backscattering while entering the multiplication mode. We conclude that the electric field effects observed here, would also apply for other photocathodes and gas mixtures. An enhancement of the QE after microdischarges was observed and is discussed in detail.

A multiconfiguration self-consistent reaction field response method

A multiconfiguration self-consistent reaction field linear response method is presented for calculating frequency-dependent molecular properties as well as electronic excitation energies and transition moments of solvated molecules. Sample calculations are presented of a solvated water molecule and show a substantial dependence on the properties of the surrounding solvent. The solvent effect cannot be described as a correction to the vacuum value involving simple scalar factors.

Hidden gravity in open-string field theory.

We clarify the nature of the graviton as a bound state in open-string field theory: The flat metric in the action appears as the vacuum value of an OPEN string field. The bound state appears as a composite field in the FREE field theory.

RS 7 Reliability of apical dye sealability studies with and without vacuum removal of air inclusions

The reliability of two commonly used methods of sealability testing, dye leakage under normal atmospheric pressure and dye leakage in a vacuum, was tested using a repeated studies design. Forty extracted teeth were instrumented and obturated using lateral condensation of gutta-percha and Sealapex® sealer. One half of the teeth were placed in India ink under normal atmospheric pressure and the other half underwent air evacuation before immersion in the ink. After 24 hours the teeth were removed from the ink and rendered transparent for linear leakage analysis. A second study, repeated within the exact parameters of the first, was performed approximately one month later. MannWhitney U tests indicated that there was no significant difference between the air and vacuum groups or within each group (air or vacuum) between trials, indicating that the methodology is repeatable and that application of vacuum did not enhance the reliability. Most of the teeth placed under vacuum showed evidence of vacuum induced artifacts that may negate the vacuum's value as a research tool.

What can we learn from a second phi meson peak in ultrarelativistic nuclear collisions?

The decay width of a phi meson is reduced from its vacuum value as its mass decreases in hot hadronic matter as a result of the partial restoration of chiral symmetry. This reduction is, however, cancelled by collisional broadening through the reactions $\phi\pi\to KK^*$, $\phi K\to\phi K$, $\phi\rho\to KK$, and $\phi\phi\to KK$. The resulting phi meson width in hot hadronic matter is found to be less than about 10 MeV for temperatures below 200 MeV. If hadronic matter has a strong first-order phase transition, this narrow phi meson with reduced mass will appear as a second peak in the dilepton spectrum in ultrarelativistic heavy ion collisions. We discuss use of this second phi peak to determine the transition temperature and the lifetime of the two-phase coexistence region in the case of a strong first-order phase transition. We also discuss using the peak to determine the range of temperatures over which the transition occurs in the case of a smooth but fast change in the entropy density.

Electron extraction from a CsI photocathode into condensed Xe, Kr, and Ar

We have studied the electron extraction from a CsI photocathode into gaseous (0–55 atm) and liquid Xe, Kr, and Ar. Two experimental setups were used. In the first one the photocathode was irradiated with a UV lamp and the photocurrent was directly measured. In the liquid phase, the QE was 2–3 times higher than that in vacuum for LXe and LKr. In LAr, 50% of the vacuum value was achieved. For Xe at a pressure higher than 50 atm, we observed that the QE increased with increasing pressure and gave a value higher than that measured in vacuum. In the second setup, 5.5 MeV alpha particles were used as the source of ionization and scintillation in the liquids, and both the charge and scintillation signals were measured. From the scintillation signal, the intrinsic energy resolution was measured to be 2.8%, 5.2% and 8.4% FWHM, respectively, in LXe, LKr and LAr. Stable operation was demonstrated for all three cryogenic liquids.

PHOTOEMISSION CALCULATION WITH KRONIG-PENNEY MODEL

Photoemission calculations have been performed using the Kronig-Penney model and including photon field variation with the help of a simple model, where the dielectric response in the surface region is a local function linearly interpolated between the vacuum value and the experimentally measured bulk value. Results with different dielectric functions are also presented.

The coupling of quark and gluon condensates in hot and dense systems

Two lagrangians, which implement the QCD scale anomaly, are used to study the coupling of quark and gluon condensates in dense and hot matter. The response of the system strongly depends on the assumed value of the vacuum gluon condensate. For a low value of this vacuum gluon condensate, quark and gluon condensates feel simultaneously the chiral phase transition while for a larger value, the gluon condensate keeps its vacuum value and the quark condensate is the only order parameter of the transition. We also calculate in both models the equation of state of nuclear matter.

Quark condensate at finite baryon density.

We discuss a recently derived, model-independent relation that expresses the value of a medium-modified quark condensate in terms of the vacuum value of the condensate and the value of the nucleon sigma term, [sigma][sub [ital N]]. Our goal is to calculate the value of the quark condensate in nuclear matter, [l angle]NM[vert bar][ital [bar q]](0)[ital q](0)[vert bar]NM[r angle], using some standard many-body techniques. Here, we comment on the mean-field calculations of Cohen, Furnstahl, and Griegel and others. We then calculate the value of the nuclear matter quark condensate using linear response theory. In a sigma-dominance model, the linear response calculation relates the modification of the vacuum condensate to the matrix element of the operator [ital [bar q]q] taken between a state of the sigma meson and the vacuum. (That matrix element may be used to define a sigma decay constant, [ital f][sub [sigma]].) We also provide some additional insight into the relation between the dynamics of the quark condensate and the scalar fields of relativistic nuclear physics.

Nonlinear self-consistent theory for crossed-field devices.

A closed, nonlinear set of fluid equations that is based on the electron guiding-center orbits and is generally applicable to the analysis of crossed-field, slow-wave devices, is developed. The equations are used to model the behavior of the crossed-field amplifier. The dielectric response from the spoke charge is self-consistently included. A mean-field approximation is introduced to express the effect of the spoke charge on the rf mode profile. The dielectric modifications are then parametrized by an average amplitude factor \ensuremath{\Lambda}^ and an average phase shift \ensuremath{\psi}^ from the vacuum values. In the synchronous with the rf signal frame of reference the streamlines follow the equipotential surfaces of the transformed fields. In the steady state, the flow is incompressible. A uniform-density, constant-height electron hub feeds the current spokes. The secondary electron production at the cathode is computed self-consistently through the secondary-emission coefficient and the average impact energy. The spoke current is determined by the difference of the E\ifmmode\times\else\texttimes\fi{}B drift at the top of the hub from the rf phase velocity. At small space-charge density relative to the Brillouin density, the dielectric corrections enter as a rotation ${\mathit{e}}^{\mathit{i}\mathrm{\ensuremath{\psi}}\mathrm{^}}$ of the complex growth rate relative to the growth without spoke self-fields. The numerical solutions for arbitrary space charge are compared with previous results without spoke-field effects. An increase in the rf gain and in the anode dc current is observed at any given operation point, despite a small drop in the efficiency. It is concluded that the increase in the rf field strength in the anode-cathode space, caused by the spoke self-field, compensates for the detuning effects from the modifications on the rf mode profile. In reentrant devices, the recycling of the space charge further increases the output power and the level of noise generated by the output-input feedback.

Ionization-induced defocusing of intense laser pulses in high-pressure gases

Two-dimensional simulation results are presented for the case of an intense ultrashort laser pulse propagating through an initially neutral high-pressure gas. The combined effects of diffraction and ionization lead to self-defocusing of the pulse, which reduces the peak intensity from its vacuum value and restricts the maximum achievable plasma density. The effects of gas pressure and focusing geometry are investigated, and the impact of defocusing on relevant experiments is discussed.

PPP method for analysis of electromagnetic fields in inhomogeneous media

A perturbation/iterative method (the PPP method) is proposed for the analysis of electromagnetic fields in inhomogeneous media. It consists of increasing the values of the parameters the medium at all points in small increments, starting from their vacuum values, and computing the induced sources by means of the total field (the incident field, plus that of the induced sources as obtained in the preceding step). Thus, in all the perturbation/iterative steps the total excitation field is known, and therefore the solution of any problem using the method is based solely on the expression for the field of an elemental source in a vacuum. The method appears to be very versatile, conceptually the simplest possible and remarkably rapid. It also has extremely low memory requirements even for very large problems, provided that computing time is not critical. In addition, it can be combined very efficiently with other available methods, e.g. with the method of moments for the analysis of conducting antennas in a vacuum to analyse such antennas in the presence of arbitrary dielectric or magnetic bodies.

Skin compliance: Measuring skin consistency in the spinal region of healthy children and adults

A vacuum tissue compliance meter was used for objective documentation of soft tissue consistency in the spinal region of 20 healthy children and 20 healthy adults. The paraspinal measurements were taken at levels C6, T1, T3, T6, T10, L3 and L5 with increasing vacuum values of between 2 and 25 kPa. Differences between the spinal levels were significant. The greatest amount of skin compliance was found at level C6; levels decreased from the cervical to the lumbar level with a slight increase at level T10. The children were shown to have more skin compliance than the adults, and the females more than the males. Both intra- and inter-observer reliability were satisfactory. Measurements on both sides correlated highly. No significant differences could be found between the measurements of the two investigators. The maximum regional differences were measured using a vacuum of 15 kPa. There was no significant difference between measuring the skin in the morning or afternoon. Skin compliance was not related to sub...

Weird muonium diffusion in solid xenon

Muon and muonium spin rotation and relaxation parameters were studied in liquid and solid xenon. The small diamagnetic fraction (∼10%) observed in condensed xenon is believed to be Xeμ +. The muonium hyperfine frequency was measured for the first time in liquid Xe and was found to be in agreement with the vacuum value. A nonmonotonic temperature dependence of the muonium relaxation rate probably indicates that muonium diffusion in solid Xe is of quantum nature.

Packaging Cooked Turkey Meat Patties while Hot Reduces Lipid Oxidation

ABSTRACTElimination of oxygen by “hot packaging” reduced the 2‐thiobarbituric acid reactive substances (TBARS) value of meat patties by about 50% in control and myoglobin added, and between 30‐40% in ferrous iron added turkey patties, as compared with “cold packaging.” The TBARS values of hot and cold vacuum packaged patties were significantly lower than those of loosely packaged patties after 1 wk refrigerated storage. Most lipid oxidation in meat patties occurred at day 0, and only small changes in TBARS values were observed after 1 wk storage. Although the prooxidants in meat were major factors in promotion of lipid oxidation of cooked meat, hot packaging minimized their effects.

Optical guiding and the relative phase in free-electron lasers

Abstract The relationship between the relative phase (defined as the shift in the wavenumber from the vacuum value integrated over the interaction length) and optical guiding in the free-electron laser is studied. The relative phase must be positive for the refractive guiding of the signal. The relative phase is studied from the standpoint of the low gain regime, and is found to be negative at the low frequency end of the gain band and to increase with increasing frequency until it turns positive at a frequency approximately 10% below the frequency of peak gain. Thus, optical guiding is indicated over a large portion, but not all, of the gain band. A quantitative measure of the optical guiding of the signal is obtained by an analytic formulation of the guiding of the signal, based upon a separable beam approximation in which the evolution of the signal is determined by a Green's function analysis. It is shown that the analytic result is in substantial agreement with the calculation of the relative phase.

Nonlinear σ-model and nucleon structure

The nonlinear σ-model with the Wess-Zumino action describes the nucleon as a soliton and incorporates the non-abelian chiral anomalies. Several studies have shown that the model works well except for the nucleon mass, which comes out consistently too large. We investigate this question beginning with the more general framework of the linear σ-model, which has besides a pseudoscalar meson sector, a fermion or quark sector, a scalar field and an interaction between the fermions via the scalar field. Using a path integral formulation, we express the fermion measure of the model as the product of a Jacobian and an invariant measure. Identifying this Jacobian as exp[iΓwz] , we find that the model breaks up into two parts, when in the pseudoscalar meson sector the scalar field is replaced by its vacuum value. The pseudoscalar part of the model becomes the nonlinear σ-model with the Wess-Zumino actionΓwz. The other part involves chiral fermions, the scalar field and their interaction. We continue this part back to the Minkowski space to determine its ground state and energy levels. We find that for a scalar field that vanishes at smallr, but rises sharply to its vacuum value at someR, the ground state energy of the interacting quark-scalar-field system can be lower than the ground state energy of the non-interacting quark system. This means the interaction between quarks and the scalar field can lead to a condensed ground state or vacuum and can reduce the overall energy of the system (a phase transition as in superconductivity). It is, therfore, not surprising that the nonlinear σ-model predicts too large a nucleon mass, since it implicitly assumes a normal non-interacting vacuum in the quark sector. Quarks are now quasiparticles that appear as excitations of the condensed vacuum. The nucleon structure that emerges from this investigation agrees fully with the phenomenological nucleon structure found from analysis of high energy elasticpp and\(\bar p\)p scattering at CERN ISR and SPS Collider.

Quark and gluon condensates in nuclear matter.

Quark and gluon condensates in nuclear matter are studied. These in-medium condensates may be linked to a wide range of nuclear phenomena and are important inputs to QCD sum-rule calculations at finite density. The Hellmann-Feynman theorem yields a prediction of the quark condensate that is model independent to first order in the nucleon density. This linear density dependence, with slope determined by the nucleon \ensuremath{\sigma} term, implies that the quark condensate is reduced considerably at nuclear matter saturation density---it is roughly 25--50 % smaller than the vacuum value. The trace anomaly and the Hellmann-Feynman theorem lead to a prediction of the gluon condensate that is model independent to first order in the nucleon density. At nuclear matter saturation density, the gluon condensate is about 5% smaller than the vacuum value. Contributions to the in-medium quark condensate that are of higher order in the nucleon density are estimated with mean-field quark-matter calculations using the Nambu--Jona-Lasinio and Gell-Mann--L\'evy models. Treatments of nuclear matter based on hadronic degrees of freedom are also considered, and the uncertainties are discussed.