4,948 research outputs found
Hyperfine structure of S-states in muonic deuterium
On the basis of quasipotential method in quantum electrodynamics we calculate
corrections of order and to hyperfine structure of S-wave
energy levels of muonic deuterium. Relativistic corrections, effects of vacuum
polarization in first, second and third orders of perturbation theory, nuclear
structure and recoil corrections are taken into account. The obtained numerical
values of hyperfine splitting meV (1S state) and
meV (2S state) represent reliable estimate for a
comparison with forthcoming experimental data of CREMA collaboration. The
hyperfine structure interval meV can be used for precision check of quantum
electrodynamics predictions for muonic deterium.Comment: 18 pages, 7 figure
Radiative nonrecoil nuclear finite size corrections of order to the Lamb shift in light muonic atoms
On the basis of quasipotential method in quantum electrodynamics we calculate
nuclear finite size radiative corrections of order to the
Lamb shift in muonic hydrogen and helium. To construct the interaction
potential of particles, which gives the necessary contributions to the energy
spectrum, we use the method of projection operators to states with a definite
spin. Separate analytic expressions for the contributions of the muon
self-energy, the muon vertex operator and the amplitude with spanning photon
are obtained. We present also numerical results for these contributions using
modern experimental data on the electromagnetic form factors of light nuclei.Comment: 8 pages, 1 Figur
Towards a Complete Twistorization of the Heterotic String
In and 10 space--time dimensions considered is a string model
invariant under transformations of space--time supersymmetry and
local worldsheet supersymmetry with the both Virasoro constraints solved in the
twistor form. The twistor solution survives in a modified form even in the
presence of the heterotic fermions.Comment: 11 pages, latex, report no. Goteborg-ITP-94-1
On Dimensional Degression in AdS(d)
We analyze the pattern of fields in d+1 dimensional anti-de Sitter space in
terms of those in d dimensional anti-de Sitter space. The procedure, which is
neither dimensional reduction nor dimensional compactification, is called
dimensional degression. The analysis is performed group-theoretically for all
totally symmetric bosonic and fermionic representations of the anti-de Sitter
algebra. The field-theoretical analysis is done for a massive scalar field in
AdS(d+d) and massless spin one-half, spin one, and spin two fields in
AdS(d+1). The mass spectra of the resulting towers of fields in AdS(d) are
found. For the scalar field case, the obtained results extend to the shadow
sector those obtained by Metsaev in [1] by a different method.Comment: 30 page
Emission of ions and charged soot particles by aircraft engines
In this article, a model which examines the formation and evolution of chemiions in an aircraft engine is proposed. This model which includes chemiionisation, electron thermo-emission, electron attachment to soot particles and to neutral molecules, electron-ion and ion-ion recombination, ion-soot interaction, allows the determination of the ion concentration at the exit of the combustor and at the nozzle exit of the engine. It also allows the determination of the charge of the soot particles. For the engine considered, the upper limit for the ion emission index EI<sub>i</sub> is of the order of (2-5) x10<sup>16</sup> ions/kg-fuel if ion-soot interactions are ignored and the introduction of ion-soot interactions lead about to a 50% reduction. The results also show that most of the soot particles are either positively or negatively charged, the remaining neutral particles representing approximately 20% of the total particles. A comparison of the model results with the available ground-based experimental data obtained on the ATTAS research aircraft engines during the SULFUR experiments (Schumann, 2002) shows an excellent agreement
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