The Effect on the Lifetime of an Atom Undergoing a Dipole Transition Due to the Presence of a Resonating Atom

First order perturbation analysis of atom lifetime undergoing dipole transition due to presence of resonating ato

Properties of Bose-Mesons

The Thesis contains an analysis of the properties of the pi-meson. Current meson theory is used in an attempt to distinguish between possible meson types. After a survey of the experimental data involving mesons as real particles, there is a brief summary of the theory involved. An approximate method is proposed for the computation of cross-sections for meson processes involving matrix elements over exact nucleon eigenstates. The validity of this approach, the distorted wave approximation, is considered in detail for spin zero mesons. Comparison is also made with other phenomenological approaches. The distorted wave approximation is used to calculate cross-sections for the production of pi-mesons in nucleon-nucleon collisions under certain simplifying assumptions concerning the nuclear forces. For a final continuous nuclear relative motion, it is found that low energy nucleon states are favoured. This, in the case of a final neutron-proton system, together with a large contribution from transitions to a final bound deuteron, leads to a meson spectrum well peaked at the highest allowed energies in agreement with recent experiments. The total cross-section depends more on the shape and size of the inter-nucleon potential than on the meson type, but the spectrum at a given angle, and, more particularly, the angular distribution, are critically dependent on the parity of the meson produced. A comparison with experiment favours scalar mesons. There is also a consideration of the relatively small cross-section for the production of neutral pi-mesons in the observations of simple collisions. The absorption of pi-mesons by nuclei is then discussed on the assumption that capture takes place from the close shells of the meson-nuclear system. Detailed calculations are presented for the direct capture by heavy nuclei, and for various capture processes in Deuterium. When compared with recent observations, the selection rules for the absorption of mesons in light nuclei favour pseudoscalar mesons. The final problem considered is of a different character, and consists of a field theoretical calculation using Pauli regulators with the Feynman technique. It concerns the decay of heavy neutral bosons to two pi-mesons through an assumed nucleon coupling. Comparison is made with the various V-meson decays reported in cosmic ray photographs. Chapter Six summarises the contemporary position of the relation of meson theory in the light of the calculations presented in this paper, with experiment

Explaining Violation Traces with Finite State Natural Language Generation Models

An essential element of any verification technique is that of identifying and communicating to the user, system behaviour which leads to a deviation from the expected behaviour. Such behaviours are typically made available as long traces of system actions which would benefit from a natural language explanation of the trace and especially in the context of business logic level specifications. In this paper we present a natural language generation model which can be used to explain such traces. A key idea is that the explanation language is a CNL that is, formally speaking, regular language susceptible transformations that can be expressed with finite state machinery. At the same time it admits various forms of abstraction and simplification which contribute to the naturalness of explanations that are communicated to the user

Microscopic Theory of Spontaneous Decay in a Dielectric

The local field correction to the spontanous dacay rate of an impurity source atom imbedded in a disordered dielectric is calculated to second order in the dielectric density. The result is found to differ from predictions associated with both "virtual" and "real" cavity models of this decay process. However, if the contributions from two dielectric atoms at the same position are included, the virtual cavity result is reproduced.Comment: 12 Page

Improved LeRoy-Bernstein near-dissociation expansion formula. Tutorial application to photoassociation spectroscopy of long-range states

NDE (Near-dissociation expansion) including LeRoy-Bernstein formulas are improved by taking into account the multipole expansion coefficients and the non asymptotic part of the potential curve. Applying these new simple analytical formulas to photoassociation spectra of cold alkali atoms, we improve the determination of the asymptotic coefficient, reaching a 1% accuracy, for long-range relativistic potential curve of diatomic molecules.Comment: This article is part of Daniel Comparat's PhD thesis available at http://tel.ccsd.cnrs.fr

Spatial Control of Photoemitted Electron Beams using a Micro-Lens-Array Transverse-Shaping Technique

A common issue encountered in photoemission electron sources used in electron accelerators is the transverse inhomogeneity of the laser distribution resulting from the laser-amplification process and often use of frequency up conversion in nonlinear crystals. A inhomogeneous laser distribution on the photocathode produces charged beams with lower beam quality. In this paper, we explore the possible use of microlens arrays (fly-eye light condensers) to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes. We also demonstrate the use of such microlens arrays to generate transversely-modulated electron beams and present a possible application to diagnose the properties of a magnetized beam.Comment: arXiv admin note: text overlap with arXiv:1609.0166

Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core.

Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass of Cladophora surveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by "top-down" (consumer release) rather than "bottom-up" (growth promoting) controls

Scaling Symmetries of Scatterers of Classical Zero-Point Radiation

Classical radiation equilibrium (the blackbody problem) is investigated by the use of an analogy. Scaling symmetries are noted for systems of classical charged particles moving in circular orbits in central potentials V(r)=-k/r^n when the particles are held in uniform circular motion against radiative collapse by a circularly polarized incident plane wave. Only in the case of a Coulomb potential n=1 with fixed charge e is there a unique scale-invariant spectrum of radiation versus frequency (analogous to zero-point radiation) obtained from the stable scattering arrangement. These results suggest that non-electromagnetic potentials are not appropriate for discussions of classical radiation equilibrium.Comment: 13 page